Method and system for electrochemical reduction of carbon dioxide employing a gas diffusion electrode

[0001] The present invention relates generally in the field of electrochemical reactions, in particular methods and systems for reducing carbon dioxide to reduction products.

Burning fossil fuels in businesses such as power generation, transportation, and manufacturing produces billions of tonnes of carbon dioxide annually. Studies since the 1970s show that increased concentrations of carbon dioxide in the atmosphere can cause changes in Earth's weather, changes in ocean pH, and other potential damaging effects. It is shown. Countries around the world, including the United States, may be looking for ways to reduce carbon dioxide emissions.

[0003] One means may be to convert carbon dioxide into economically valuable substances such as fuels and industrial chemicals. Chemicals that can reduce carbon dioxide emissions and store renewable energy for subsequent use, where energy from renewable sources can be used to convert carbon dioxide. It will be possible to both convert to. Electrochemical and photochemical pathways may be promising mechanisms for carbon dioxide conversion.

[0004] The present invention is a method and system for reducing carbon dioxide. The method accepts hydrogen gas in the anode fluid region of an electrochemical cell containing an anode containing a gas diffusion electrode.<u style="single">To do,</u>Accepts anolyte supply flow in the anolyte region of the electrochemical cell<u style="single">To do,</u>Then, in the cathode liquid region of the electrochemical cell containing the cathode, the cathode liquid supply stream containing carbon dioxide and alkali metal bicarbonate is received.<u style="single">、</u>May include. The method may include applying a potential between the anode and the cathode sufficient to reduce carbon dioxide to at least one reduction product.

[0005] It should be understood that the general description above and the detailed description below are merely examples and explanations and are not necessarily limited to the present invention. The accompanying drawings included in the specification and forming a part thereof show the subject matter of the present invention. These descriptions and drawings together illustrate the principles of the invention.

[0006] Many advantages of the present invention can be better understood by those skilled in the art by reference to the accompanying drawings.

<figref num="1A">FIG. 1A shows a system for producing oxalic acid according to one aspect of the present invention, starting with the electrochemical production of carbon monoxide from carbon dioxide.</figref><figref num="1B">FIG. 1B shows a system according to the present invention for producing oxalic acid using hydrogen halide in an anode solution to co-produce halogen.</figref><figref num="2A">FIG. 2A shows a system for producing oxalic acid according to one aspect of the invention, starting with the electrochemical formation of formate with carbon dioxide.</figref><figref num="2B">FIG. 2B shows the production of oxalic acid via carbon dioxide and hydrogen halide in the anode solution to electrochemically produce formate to co-produce halogen according to one aspect of the present invention. The system for doing so is shown.</figref><figref num="3">FIG. 3 shows a system for producing alkali metal formate using carbon dioxide according to one aspect of the present invention.</figref><figref num="4">FIG. 4 shows a system for electrochemically acidifying an alkali metal oxalate according to one aspect of the present invention.</figref><figref num="5">FIG. 5 shows, according to one aspect of the present invention, for producing alkali metal formate using carbon dioxide and alkali metal chloride brine in an anode solution to co-produce chlorine and alkali metal bicarbonate. Indicates the system.</figref><figref num="6">FIG. 6 shows a system for producing alkali metal formate using carbon dioxide to co-produce chlorine, alkali metal hypochlorite (MOCl), and oxalic acid according to one aspect of the present invention. ..</figref><figref num="7">FIG. 7 shows a system for producing formic acid solutions and oxygen co-products using carbon dioxide and a three-compartment electrochemical cell configuration according to one aspect of the invention.</figref><figref num="8">FIG. 8 shows a system for producing formic acid solution and chlorine co-products using carbon dioxide and HCl and a three-compartment electrochemical cell configuration according to one aspect of the invention.</figref><figref num="9">FIG. 9 shows an oxalic acid solution product and an oxygen co-product using carbon dioxide, a thermal reactor for converting formate to oxalate, and a three-compartment electrochemical cell configuration according to one aspect of the invention. The system for manufacturing is shown.</figref><figref num="10">FIG. 10 shows an oxalic acid solution product and a chlorine co-product using carbon dioxide, a thermal reactor for converting formate to oxalate, and a three-compartment electrochemical cell configuration according to one aspect of the invention. The system for manufacturing is shown.</figref><figref num="11">FIG. 11 shows a system using formic acid produced in an electrochemical system for use in an off-peak power energy storage system according to one aspect of the invention.</figref><figref num="12">FIG. 12 is a schematic diagram showing an electrochemical cell using hydrogen GDE for the anodic reaction in the production of oxalic acid from the reduction of carbon dioxide according to one aspect of the present invention.</figref><figref num="13">FIG. 13 is a schematic diagram showing an electrochemical cell using hydrogen GDE for the anodic reaction and carbon dioxide GDE for the cathodic reaction in the production of alkali metal formate from the reduction of carbon dioxide according to one aspect of the present invention. Is.</figref><figref num="14">FIG. 14 is a schematic diagram showing three different anode GDE structures used within an electrochemical cell in the production of alkali metal formate from the reduction of carbon dioxide according to one aspect of the invention.</figref><figref num="15">FIG. 15 is a schematic diagram showing three different cathode GDE structures used within an electrochemical cell in the production of alkali metal formate from the reduction of carbon dioxide according to one aspect of the invention.</figref><figref num="16">FIG. 16 is a schematic diagram showing an electrochemical cell using a hydrogen GDE and a weir-type solution distribution system for the anodic reaction in the production of alkali metal formate from the reduction of carbon dioxide according to one aspect of the present invention.</figref><figref num="17">FIG. 17 shows an electrochemical cell using hydrogen GDE for the anodic reaction and carbon dioxide GDE for the cathodic reaction in the production of alkali metal formate from the reduction of carbon dioxide according to one aspect of the present invention. It is a schematic diagram which shows the type solution distribution system.</figref><figref num="18">FIG. 18 shows a potential chemical derivative, starting with oxalic acid as the initial chemical feed material, according to one aspect of the invention.</figref><figref num="19">FIG. 19 shows, according to one aspect of the present invention, electrochemically converting carbon dioxide to oxalic acid, then electrochemically converting it to glycolic acid, and converting glycolic acid to glycerin by reductive amination. The system for.</figref><figref num="20">FIG. 20 shows an electrochemical cell for reducing oxalic acid to produce a glyoxylic acid product according to one aspect of the invention.</figref><figref num="21">FIG. 21 shows a batch reactor system for converting glyoxylic acid to glycerin according to one aspect of the invention.</figref>

[0007] Here, the disclosed subject matter shown in the accompanying drawings will be described in detail. [0008] The present disclosure describes methods and systems for reducing carbon dioxide. The method receives hydrogen gas in the anode fluid region of the electrochemical cell containing the anode containing the gas diffusion electrode; receives the anode fluid supply flow in the anode fluid region of the electrochemical cell; the cathode of the electrochemical cell containing the cathode. In the liquid region, it may include accepting a cathode liquid supply stream containing carbon dioxide and alkali metal bicarbonate; The method may include applying a potential between the anode and the cathode sufficient to reduce carbon dioxide to at least one reduction product.

[0009] Further, the present disclosure describes methods and systems for producing carboxylic acid-based chemicals such as carboxylic acids and salts. In this method, an electrochemical cell and a cathode reduction reaction can be used to generate carbon monoxide (CO) or alkali metal formate from a carbon dioxide supply material. A thermal reaction involving the addition of a small amount of alkali metal hydroxide catalyst can be used, for example, to combine two alkali metal formate molecules into an alkali metal oxalate product.

[0010] Alkali metal oxalates can then be converted to oxalic acid by a membrane-based electrochemical acidification process, in which protons (H) formed at the anode.⁺Alkali metal ions can be replaced with alkali metal ions (M).⁺) Can be captured as alkali metal hydroxides (MOH) at the cathode and recirculated for use as alkali metal hydroxides for use in thermal intermolecular condensation process unit operations.

[0011] Alternatively, alkali metal oxalates are HCl, HBr, HI, H.₂SO₄, H₃PO₄It can be converted to oxalic acid by treatment with mineral acids such as. For example, sodium oxalate can be treated with an aqueous HCl solution to produce an oxalic acid solution containing NaCl. Oxalic acid can be extracted from the solution by extraction with an organic solvent such as alcohol, ether, halo organic compound, ketone, amide, or ester. Useful solvents include methanol, ethanol, propanol, diethyl ether, methyl ethyl ether, methyl tert-butyl ether, tetrahydrofuran, dioxane, methylene chloride, chloroform, carbon tetrachloride, chlorobenzene, dichlorobenzene, methyl acetate, ethyl acetate, propionate. Examples include, but are not limited to, methyl, ethyl propionate, acetone, butanone, dimethylformamide, N-methylpyrrolidone and the like. Oxalic acid can also be recovered from solution by crystallization from aqueous solution. Crystallization may require concentration of the solution by evaporation and / or by cooling the solution.

[0012] After removing the oxalic acid, the aqueous solution containing the salt (eg NaCl) can be recirculated by sending it to the anodic solution compartment of the electrochemical cell. Halide ions (eg chlorides) can be oxidized to form halogens (eg chlorine). Halogen can be isolated from the anodic fluid stream after draining from the anodic fluid compartment of the electrochemical cell. Halogen can react with hydrogen produced during the hot or burning reaction of hydrogen, for example alkali metal formate, to alkali metal oxalate. Hydrogen can also be obtained from other sources. Mineral acids (eg, HCl) formed by the reaction of hydrogen with halogen can be used to acidify alkali metal oxalates to complete the cycle. The energy (heat or electrical energy) produced by reacting halogen with hydrogen can be captured and used in other processes (eg in a thermal or burning reaction) or elsewhere.

[0013] Prior to elaborating any aspect of the invention, these aspects may not be limited in this application by the structural or functional details shown in the following description or in the drawings. Should be understood. It may be possible to carry out or carry out different embodiments in different ways. It should also be understood that the expressions and terminology used herein are for illustration purposes only and should not be considered limiting. In the present specification, the use of terms such as "etc.", "contains", or "has", and variations thereof generally includes the matters listed thereafter and their equivalents, and further matters. Is intended to be. Moreover, unless otherwise indicated, technical terms can be used according to normal usage. Furthermore, it is intended that similar reference numbers may represent similar components and their equivalents.

[0014] With reference to FIG. 1A, for the production of a dicarboxylic acid, such as oxalic acid, according to one aspect of the invention, which begins with the electrochemical production of formate from the electrochemical reduction of carbon dioxide. System 100 is shown. The system 100 can include an electrochemical cell 110. The electrochemical cell 110 (also referred to as a container, electrolytic cell, or cell) can be implemented as a divided cell. The divided cell may be a divided electrochemical cell and / or a divided photoelectrochemical cell. The electrochemical cell 110 can include an anode liquid region and a cathode liquid region. The anolyte and catholyte regions can refer to compartments, sections, or generally enclosed spaces, etc., without departing from the scope and intent of the present invention.

[0015] The cathode liquid region may include a cathode. The anode liquid region can include an anode. An energy source (not shown) allows an electric potential to be generated between the anode and cathode of the electrochemical cell 110. The potential may be a DC voltage. The energy source can be configured to supply a variable voltage or constant current to the electrochemical cell 110. The separator allows the flow of ions between the anolyte region and the catholyte region to be selectively controlled. Separators can include ionic conductive polymer-based membranes, ionic conductive inorganic materials, polymer / inorganic-based membrane combinations, or diaphragm materials such as stretched PTFE (polytetrafluoroethylene).

[0016] The electrochemical cell 110 undergoes electrochemical reduction of carbon dioxide in the electrochemical cell to carry out sulfuric acid (H).₂SO₄) Is used, it can be operated to produce carbon monoxide (CO) and hydrogen as cathode products, and oxygen as an anode product.

[0017] The CO produced from the electrochemical cell 110 can be separated from hydrogen and then sent to the thermal reactor 120. The thermal reactor 120 can react carbon monoxide with an alkali metal hydroxide such as KOH by a thermal intermolecular condensation reaction to form an alkali metal formate. The thermal reactor 120 can be operated to carry out a pyrolysis reaction or a carbonylation reaction, which may be a reaction that introduces CO into organic and inorganic chemical structures.

The alkali metal formate formed from the thermal reactor 120 can be sent to another thermal reactor 130. The thermal reactor 130 can carry out a second thermal intermolecular condensation reaction using alkali metal hydroxides (eg KOH) that can accelerate the reaction to produce alkali metal oxalates. System 100 in FIG. 1 shows a thermal reactor 120 and a thermal reactor 130, but it is intended that a single thermal reactor can be used with respect to the system 100 without departing from the scope and intent of the present invention. To.

[0019] The alkali metal oxalate from the thermal reactor 130 can be dissolved in water and sent to the electrochemical acidifying electrolytic cell 140. The electrochemical acidification electrolytic cell 140 can generate a dicarboxylic acid such as oxalic acid and KOH together with oxygen and hydrogen by-products. The electrochemical acidifying electrolytic cell 140 may be a membrane-based unit containing at least three regions including an anode region, one or more central ion exchange regions, and a cathode region. An energy source (not shown) can generate a potential sufficient to generate oxalic acid between the anode and cathode of the electrochemically acidifying electrolytic cell 140. The alkali metal oxalate can be passed through the central ion exchange region, where the alkali metal ions can be substituted with protons, where the substituted alkali metal ions are sent through the adjacent membrane into the cathode region. To form alkali metal hydroxides (eg KOH). The anodic reaction can generate oxygen and hydrogen ions using an acid such as sulfuric acid.

[0020] In another embodiment, the hydrogen by-products obtained from the electrochemically acidifying electrolytic cell 140 can be used as a fuel for producing water vapor, or other hydrogen-based methods such as hydrogenation processes. It can be used in chemical processes.

[0021] Dicarboxylic acids such as oxalic acid products can be purified to produce the final purified product, or can be used with reduction or catalytic hydrogenation processes such as electrochemical reduction, such as monoethylene glycol. Can be further treated as a chemical intermediate for the production of other products.

[0022] The aqueous KOH solution from the electrochemically acidified electrolytic cell 140 can be sent to the evaporator 150. The evaporator 150 evaporates water from the KOH aqueous solution product using steam or other heat source and has a water content of 5% or less depending on the needs in the electrochemical cell 110 and the thermal reactor 120. It can be changed to a concentrated aqueous solution and / or a solid.

[0023] With reference to FIG. 1B, a system for co-producing bromine by producing a dicarboxylic acid such as oxalic acid in an anolyte using a hydrogen halide such as HBr, according to one aspect of the invention. 105 is shown. System 105 operates with a less energy-intensive electrochemical process using HBr as the anode solution in the anode region of the electrochemical cell 110 and the electrochemically acidified electrolytic cell 140, resulting in a significantly lower anode. Bromine and hydrogen ions can be generated at the potential. Bromine can then be used in reactions that produce bromination chemical products such as bromination organic compounds such as bromoethane, which can then be converted to alcohols such as ethanol or a series of thermochemistry. It can be converted to monoethylene glycol in the reaction. The system 105 shown with the thermal reactor 120 and the thermal reactor 130 is intended to be implemented using a single thermal reactor without departing from the scope and intent of the present invention. To.

[0024] Referring to FIG. 2A, a system 200 for producing a dicarboxylic acid, such as oxalic acid, according to one aspect of the invention, which begins by electrochemically producing formate with carbon dioxide. It is shown. System 200 can provide another system for producing oxalic acid produced by system 100 of FIG. 1A and system 105 of FIG. 1B, respectively.

The system 200 can include an electrochemical cell 110. Electrochemical cell 110 is CO₂Electrochemical reduction of carbon dioxide using an alkali metal carbonate and / or alkali metal bicarbonate cathode feed stream that can be formed from the reaction of alkali metal hydroxide with sulfuric acid (H₂SO₄) Is used, it can be operated so as to be produced together with oxygen as an anode product. The concentration of the alkali metal formate product solution from the cathode solution compartment of the electrochemical cell 110 ranges from 1% to 30% by weight or more, preferably 5% to 20% by weight as formate, based on formate ions. It may be in the range of% by weight. The corresponding% by weight of the alkali metal formate, eg, alkali metal formate, can be based on the molecular weight of the alkali metal compound.

[0026] The alkali metal formate can be sent to the thermal reactor 120. The thermal reactor 120 carries out a thermal intermolecular condensation reaction by adding a small amount of catalyst such as alkali metal hydroxide (eg KOH) that can increase the conversion yield to produce alkali metal oxalate. Can be done.

[0027] The alkali metal oxalate from the thermal reactor 120 can be dissolved in water and sent to the electrochemical acidification electrolytic cell 140. The electrochemical acidification electrolytic cell 140 can generate a dicarboxylic acid such as oxalic acid and KOH together with oxygen and hydrogen by-products. The electrochemical acidifying electrolytic cell 140 may be a membrane-based unit containing at least three regions including an anode region, one or more central ion exchange regions, and a cathode region. The alkali metal oxalate can be passed through the central ion exchange region, where the alkali metal ions can be substituted with protons, where the substituted alkali metal ions are sent through the adjacent membrane into the cathode region. To form alkali metal hydroxides such as KOH. The anodic reaction can generate oxygen and hydrogen ions using an acid such as sulfuric acid.

[0028] In another embodiment, the hydrogen by-products obtained from the electrochemically acidifying electrolytic cell 140 can be used as a fuel to generate water vapor, or hydrogen such as in a chemical hydrogenation process. It can be used in subprocesses that can be used.

[0029] Dicarboxylic acids, such as oxalic acid products, can be purified to produce the final purified product, or other products, such as monoethylene glycol, using electrochemical reduction or thermochemical processes. Can be further treated as a chemical intermediate for the production of.

[0030] The aqueous KOH solution from the electrochemically acidified electrolytic cell 140 can be sent to the evaporator 150. The evaporator 150 evaporates water from the KOH aqueous solution product using steam or other heat source and has a water content of 5% or less depending on the need in the electrochemical cell 110 or the thermal reactor 120. It can be changed to a concentrated aqueous solution and / or a solid.

[0031] with reference to FIG. 2B, according to one aspect of the invention, such as oxalic acid, via the electrochemical formation of a formate with a halogenated halogen in the anode solution using carbon dioxide. A system 205 for producing dicarboxylic acids and co-producing halogens such as bromine has been shown. System 205 may be similar to System 200, which can use hydrogen halides such as HBr as the anolyte in the anode region of the electrochemical cell 110 and the electrochemical acidifying electrolytic cell 140. The electrochemical cell 110 is capable of producing bromine and hydrogen ions at a significantly lower anode potential. Bromine can then be used in reactions that produce bromination chemical products such as bromoethane, which can then be converted to alcohols such as ethanol or monoethylene glycol in a series of thermochemical reactions. Can be converted to.

[0032] With reference to FIG. 3, a system 300 for producing formates such as alkali metal formates using carbon dioxide according to one aspect of the invention is shown. FIG. 3 shows the electrochemical reduction of carbon dioxide in the production of the alkali metal formate shown in the electrochemical cells 110 of FIGS. 2A and 2B. The electrochemical cell 110 can include an anodic solution inlet / supply stream 310 and a cathode solution inlet / supply stream 312 for producing the product 314. Product 314 is an excess of alkali metal bicarbonate (KHCO)₃) May be a solution of alkali metal formate. The anode liquid region 320 can be provided with a titanium anode 322 having an anode electrode catalyst coating facing the cation exchange membrane 330. The anode mesh screen 332 may be a folded expanded titanium screen with an anode electrocatalyst coating, providing spacing and contact pressure between the anode 322 and the cation exchange membrane 332. The cation exchange membrane 330 selectively controls the flow of ions between the cathode solution region 340 and the anode solution region 320.

[0033] The cathode liquid region 340 can be provided with a mounted cathode 342, which may be a metal electrode having an active electrocatalyst layer on the front side facing the membrane 330. A high surface area cathode structure 344 can be mounted between the surface of the cathode 342 and the cationic film 330 using direct contact pressure.

[0034] As shown in FIGS. 1A and 2A, the anodic solution region 320 may be supplied by a stream 310 which may include an anodic solution containing an aqueous sulfuric acid electrolyte solution. The flow 310 can be introduced into the anode fluid region 320 and flow through the folded anode screen 332 through the vicinity of the surface of the anode 322. For the anodic reaction, water is oxygen (O)₂) And hydrogen ion (H)⁺) Or separation into protons can be included. A mixture of gas and liquid from the anolyte region 320 can be discharged as a stream 350, which flows into the anolyte gas / liquid dissociator 354 through the vicinity of a temperature sensor 352 that monitors the solution temperature in the stream. In the dissociator 354, the gas can be exhausted as a flow 356 and the excess anodic fluid overflow is discharged as a flow 358. The flow 360 may be an outlet flow in which the gas from the anode liquid dissociator 354 is reduced, and the deionized water supply flow 362 and the sulfuric acid supply supply flow 364 are added to the recirculation flow to add the acid strength of the anode liquid. ) And maintain volume. The stream 360 to which the streams 362 and 364 are added can then be passed through an optional heat exchanger 370 with a cooling water supply 372, which then becomes the stream 310 supplied into the anolyte region 320.

[0035] The electrochemical cell 110 can include a cathode liquid region 340 containing a cathode 342 having an electrocatalyst surface facing the membrane 330. A high surface area cathode structure 344 can be mounted between the membrane 330 and the cathode 342 by the contact pressure with the cathode 342 to conduct current into the structure. A thin expanded plastic mesh insulation screen (not shown) can be used at the interface between the high surface area structure 344 and the membrane 330 to minimize direct contact of the high surface area cathode material with the membrane 330. it can.

[0036] The feed stream 312 can be fed into the cathode fluid region 340 and flow through the high surface area structure 344 and across the surface of the cathode 342, where carbon dioxide, electrolysis at the applied currents and potentials. The cathodic reduction reaction between the liquid and the cathode material produces an outlet current 314 containing formate.

[0037] Flow 314 may be the product of the outlet solution and gas mixture from the cathodic reaction, which passes in the vicinity of the pH monitoring sensor 374 and the temperature sensor 352 and then into the cathodic air / liquid dissociator 380. Flowing, where the gas is discharged as flow 382, the cathode / electrolyte overflow is discharged as flow 384, and the gas-depleted flow is discharged as flow 386 from the dissociator. The flow 386 can then be introduced at the inlet of the cathode fluid recirculation pump 390, which is then fed through a heat exchanger 392 with cooling water 372 and then through the vicinity of the temperature sensor 352. A new catholyte electrolyte feed stream 394 can be metered into the stream 386, which regulates the pH of the catholyte stream flow into the catholyte region 340 and controls the overflow rate of the product. It can be used to set the formate product concentration and the pH is monitored by sensor 374. The carbon dioxide stream 396 can be weighed into the stream introduced into the cathode solution region 340 as the stream 312.

[0038] In another embodiment, as shown in FIGS. 1B and 2B, the sulfuric acid-containing anodic solution shown in FIGS. 1A and 2A is replaced with an anodic solution containing hydrogen halide (eg, HBr) at the anode. Halides (eg, bromine) and hydrogen ions can be produced at lower potentials than required to produce oxygen. Halides can then be used in reactions that produce halide chemical products, such as bromoethane in reactions with alkanes such as ethane, which can then be converted to alcohols (eg ethanol). , Or can be converted to monoethylene glycol in a series of thermochemical reactions.

[0039] With reference to FIG. 4, a system 400 for electrochemically acidifying alkali metal oxalates according to one aspect of the invention is shown. The electrochemical acidifying electrolytic cell 140 includes an anode liquid region 402, a central ion exchange region 408 separated by cationic ion exchange membranes 406a and 406b on each side, and a cathode liquid region 410 (where alkali). It can contain metal hydroxides (eg, which can form KOH). Hydrogen ions (H) in the anolyte region 402 if potential and current can be applied to the cell⁺) Or protons can then be sent through the adjacent membrane 406a into the central ion exchange region 408. For example, an alkali metal oxalate (eg, alkali metal oxalate) product solution 405 produced in a thermal reactor (120 in FIG. 1A and 130 in FIG. 2B, respectively) can be passed through the central ion exchange region 408, where The alkali metal ion in the solution stream is replaced with a proton, thereby acidifying the solution to form a dicarboxylic acid such as oxalic acid. Flow 456 and substituted alkali metal ions can be sent into the cathode solution region 410 through the adjacent cation exchange membrane 406b, where they are hydroxide ions (OH) formed from the water reduction reaction at the cathode.^-) To form a flow of alkali metal hydroxides (eg KOH) 434.

[0040] The electrochemically acidifying electrolytic cell 140 can contain input and supply streams 430 and 432, which are a solution of a dicarboxylic acid (eg, oxalic acid) 456, an anode solution region 402 to oxygen 420, and a cathode solution region 410. KOH442 can be produced from. The anode region 402 can include a titanium anode 404 having an anode electrode catalyst coating facing the cation exchange membrane 406a. The central ion exchange region 408 can include a plastic mesh spacer to maintain space in the central ion exchange region between the cation exchange membranes 406a and 406b. In some cases, another material used within the central ion exchange region may be to use a cationic ion exchange material to increase the conductivity of the electrolyte in solution in the ion exchange region. It can also help capture and exchange cations such as potassium and improve the efficiency of proton exchange by cations. The cathode liquid region 410 can include the cathode 412.

[0041] The anodic fluid region 402 can be provided with a feed-inflow 430 containing sulfuric acid, which flows through the anodic fluid region 402 and is discharged as a flow 414 containing gas and liquid to the temperature sensor 416. It can be sent through the vicinity into the anodic fluid dissociator 418, where the gas is discharged as a stream 420 and the liquid overflows as a stream 422. The gas-reduced flow 424 can be expelled from the anolyte dissociator 418 and flows through the deionized water flow 426 and the sulfuric acid replenishment flow 428 to maintain the strength of the acid electrolyte in the anolyte region 402. It can be weighed in. The flow 424 can be sent through an optional heat exchanger 426 having a cooling water supply flow 428 to cool or maintain the temperature of the flow 424, which is introduced into the anolyte region 402 as the flow 430. To do.

[0042] The catholyte region 410 may include a feed stream 432 that may be an alkali metal hydroxide (eg, KOH) recirculating in the catholyte loop, which in the catholyte region 410. Introduced and flowed through the vicinity of the cathode 412, thereby hydrogen gas and hydroxide (OH)^-) Ions can be generated, and alkali metal hydroxides are formed by combining the alkali metal ions that cross the film 406b with the hydroxide ions that are formed at the cathode 412 by the reduction of water. The outlet flow 434 from the catholyte region 410 may contain alkali metal hydroxides and hydrogen gas from the cathodic reaction, which is sent through the vicinity of the temperature sensor 436 and then into the catholyte dissociator 438. Here, the hydrogen gas 440 can be separated from the catholyte solution, which is discharged from the cathode liquid dissociator 438 as a recirculation flow 444, and the alkali metal hydroxide product overflow flow 442 is discharged. The recirculation flow 444 can be sent through a voluntary recirculation pump 446 and then through a voluntary heat exchanger 448 with a cooling water supply 450. This stream can then be sent through the vicinity of the temperature sensor 452, and then a deionized water-added stream 454 can be added to the stream to control the alkali metal hydroxide concentration in the catholyte recirculation loop. Reintroduce into catholyte region 410 as flow 432.

[0043] In another embodiment, the anodic solution containing sulfuric acid is replaced with an anolyte containing hydrogen halide, such as HBr, at a much lower potential than is required to generate oxygen at the anode. Bromine and hydrogen ions can be generated.

[0044] Figure 5 shows, for example, a sodium-based sodium formate capable of producing sodium formate from the electrochemical reduction of carbon dioxide, then converting sodium formate to sodium oxalate, which in turn can be converted to oxalic acid. A schematic diagram of the system 500, which is another aspect of operating the system using compounds, is shown. This system produces oxalic acid in addition to two additional by-products, which may be sodium bicarbonate and sodium hydroxide.

[0045] The electrochemical cell 502 can be configured in the same manner as the electrochemical cell shown and described in FIG. 3, except that the supply solutions used in the anode solution and the cathode solution are modified. The electrochemical cell 502 can include a cathode liquid compartment 506 and an anode liquid compartment 504, and preferably an ion permeable separator 503, which is a cationic ion exchange type membrane. A feed stream 522 of saturated NaCl brine can be introduced into the cathode solution compartment 504 of the electrochemical cell 502, where the chloride ions of the NaCl salt solution can be oxidized to chlorine gas at the anode in the anode compartment 504. .. As the chloride ion of the NaCl salt is oxidized at the anode, the sodium ion moves in the potential field and is sent through the separator 503 into the cathode solution compartment 506.

[0046] The anodic solution product stream 508 from the cathodic solution compartment 504 contains a mixture of chlorine gas and a brine solution with reduced NaCl. The chlorine gas can then be separated or dissociated as a flow 510 from the flow 508 as a co-product, and the separated depleted brine solution stream 512 then dechlorinates the depleted brine and of the solid NaCl salt. The bed is used to resaturate the brine solution with NaCl, and then the metal and hardness components (eg Ca) from the brine solution.⁺, Mg⁺, And Ba⁺) To generate a purified saturated NaCl brine solution stream 522 at the level of impurities commonly used to achieve longevity operation of the separator 503, which is the anode solution compartment of the formate cell 502. It can be processed in a series of steps commonly used in a chloride-alkali process, including performing a brine purification step that electrolyzes within 504.

[0047] Chlorine gas 510 can then be treated in a variety of ways, such as removing water from the gas by condensation, and then chlorine gas is for producing a variety of useful co-products from the system. EDC (ethylene dichloride) is produced, for example, to produce sodium hypochlorite by reacting with NaOH, to produce HCl by reacting with hydrogen, and by reacting with an external supply of ethylene. It can be used to react with organic substances for such reasons. Many other reaction by-products produced with chlorine gas 510 can be recalled.

[0048] Residual chlorine from brine solution 512 depleted with brine dechlorination unit 514 and with selected reducing agents, including sodium sulfite, sodium hyposulfite, activated carbon, and hydrogen peroxide. Can be removed. The dechlorinated brine can then be sent to the brine saturater unit 516, where the depleted brine NaCl concentration is included in a bed of solid salt crystals in a brine satulator (usually called a bleiner). Can be used to increase the concentration of NaCl from 150 to 240 g / L to 300 to 320 g / L of NaCl. Saturated brine is then subjected to a brine purification system 518 (usually a chemical precipitation step to remove most of the hardness components in the solution by adding NaOH and sodium carbonate under alkaline conditions, then filtering and precipitation. The hardness component-containing solids that have been removed may then be subjected to an ion exchange purification step using a chelated ion exchange resin bed to include reducing the hardness level in the brine to typically 20-50 ppb or less. Can be sent through). The sulfate component in the brine is either due to chemical precipitation or in a commercial system that uses nanofiltration to preferentially remove the sulfate from the brine, eg Aker. It can be reduced by using the SRS system sold by Chemetics. Purified chemicals can also include HCl and NaOH used to regenerate the chelated ion exchange column. Flow 520 may be an outflow containing precipitated carbonates, sulfates, and metal effluents from the precipitation of saturated brine solution, which must be processed and recirculated back into the process for disposal. The substance can be minimized. The purified brine solution 522 can then be delivered into the anodic solution compartment 504 of the electrochemical cell 502. Recirculation of the anolyte loop is not shown, but the flow velocity of the brine can be measured so that the desired brine concentration is maintained in the anolyte loop and overflow flow 508 of the electrochemical cell, and the brine concentration is usually The amount of NaCl is in the range of 150 to 240 g / L. In one aspect, the anode fluid brine concentration can be operated at lower NaCl concentrations, such as as low as about 100-140 g / L, which reduces chlorine efficiency and produces more by-products in the chlorine gas stream. Oxygen can be produced, which can be useful in reducing the flow of brine through the brine purification system and reducing the cost of processing brine.

[0049] A solution supply that may be an aqueous mixture of sodium formate, sodium bicarbonate, and dissolved carbon dioxide, which may include gaseous carbon dioxide components that may be in the form of gaseous microbubbles. Stream 548 can be sent into the cathode solution compartment of electrochemical cell 502. Preferably in the cathodic compartment 506 incorporating a high surface area cathode structure, carbon dioxide can be electrochemically reduced to formate, which is sodium ion (Na) passing through the adjacent separator 503.⁺) Can be combined to form sodium formate. In addition, hydrogen (H) at the cathode₂Hydroxide ions (OH) due to inefficient side reactions of the cathode forming)^-) Can be produced, and these hydroxide ions can react with carbon dioxide to form sodium carbonate in the cathode solution solution. Sodium carbonate can then be further reacted with excess carbon dioxide to form sodium bicarbonate. In addition, other sodium ions can be combined with carbonic acid and other possible carbon dioxide equilibrium species at the operating cathode solution pH to further form additional sodium carbonate and sodium bicarbonate.

[0050] The reduction reaction products can be discharged as stream 524, where they can be separated or dissociated into gas stream 526 and solution stream 530. The gas stream 526 can be sent into the separator 528 to separate carbon dioxide from the by-products hydrogen so that they can be reused or recirculated in other system 500 unit operations. Can be done. The gas separator 528 may be any suitable membrane-based or molecular sieve pressure swing gas separation unit capable of separating carbon dioxide and hydrogen. The separated gas can then be further purified and compressed as needed for recirculation or reuse in the process.

[0051] Solution flow 530, primarily containing sodium formate and sodium bicarbonate, then recirculates flow 532, which can be recirculated back to the cathodic compartment of electrochemical cell 502, and generated logistics 531. It can be divided into (which can be sent to the evaporator-crystallizer 550). The recirculation flow 532 can be provided with several input streams, such as a carbon dioxide introduction stream 534 and, in some cases, a sodium bicarbonate stream 536 from the reactor-dissolver unit 560, on the side discharged from the stream 532. The stream 538 can be sent into a voluntary electrochemical acidification cell 540 to allow the acidification generation stream 546 to return into the stream 532 to prevent sedimentation in the stream 532 and the cathodic compartment 506. Addition water can be added to the stream as needed, and all of the inputs / discharges into the stream 532 can finally be sent into the catholyte compartment 506 as a solution stream 548.

[0052] The electrochemical acidification cell 540 can be used to acidify a small portion recovered from the cathode fluid loop stream 532 and then reintroduce it into the anode fluid recirculation stream 532 as the stream 546. it can.

[0053] The electrochemical acidification cell 540 may have the same design as the acidification cell shown in FIG. Sulfuric acid can be used in the anodic solution of the cell to generate oxygen and hydrogen ions by the anodic reaction, as the formate stream 538 passes through the ion exchange compartment in the cell. It can be used to acidify it. The cathodic reaction in this cell may be the reduction of water, thereby hydrogen gas and hydroxide ions (OH).^-) Is generated. Sodium ions that can be replaced by hydrogen ions sent into the ion exchange compartment can be sent into the cathode solution compartment and combined with hydroxide ions to produce a sodium hydroxide co-product. Hydrogen gas can also be captured for use in the process. Deionized water can be used to control the concentration of NaOH in the acidified cell 540 and in the cathodic compartment as needed to replace the electrolyzed water.

[0054] A cathode liquid-forming stream 531 that may contain high concentrations of alkali metal formates and alkali metal bicarbonates is sent to the evaporator-crystallizer unit 550 to evaporate sufficient water from the solution. Alkali metal bicarbonate crystal products can be continuously precipitated as flow 556, producing a liquid concentrated alkali metal formate stream 554, and a water-producing stream 552, which is condensed. , In the bicarbonate solution solubilizer 572, etc., can be used elsewhere as needed in the process. The evaporator-crystallizer 550 can use water vapor to provide the energy required to evaporate water from the stream 531 which is the flow into the unit. The evaporator-crystallizer 550 may be a multiple evaporator effect unit containing a plurality of units in order to efficiently use the energy of the input steam, or any other suitable type of unit can be used. .. In addition, the evaporator-crystallizer 550 can use mechanical manipulation to further reduce the energy required to generate water vapor, as well as vacuum to evaporate water from the solution. Any suitable evaporator-crystallizer unit or system can contain metallic materials suitable for the operating conditions of the system. Alkali metal bicarbonates can have a solubility in water that can be about 8-10 times higher than alkali metal bicarbonates, so this difference in solubility can be used to use the difference in solution temperature to make alkali metal bicarbonates. The separation can be improved by allowing for easy separation of the alkali metal halide from. Other methods for separating alkali metal formate from alkali metal bicarbonate can be used, including fractional crystallization, cooling crystallization, downflow crystallization and the like. A continuous process can be used for separation, but batch processing can also be used.

[0055] In a further embodiment, if the amount or ratio of alkali metal bicarbonate is less than 1:10 to 1:20 or less with respect to alkali metal formate, alkali metal bicarbonate is added. CO in Na-Carate Liquid Dryer 5₂Can be pyrolyzed and not recovered due to recirculation. This method can reduce the cost of additional processes in performing the separation and recirculation of alkali metal bicarbonate from alkali metal formate.

The alkali metal bicarbonate crystal stream 556 from unit 550 may be in the form of an aqueous slurry, which is then separated, washed, dried and dried by any suitable mechanism. The salt product 558 can be produced. Devices such as centrifuges and vacuum belt filters can be used to separate the alkali metal bicarbonate crystals from the 556 slurry stream, and the mother liquor from the water rinse can be recirculated back to the unit 550. it can. The alkali metal bicarbonate product 558 is also recrystallized or further purified by any suitable mechanism to produce a final product with a purity suitable for special applications such as food grade quality products. You can also get it. A portion of the slurry of stream 556 or the alkali metal bicarbonate product of stream 558 can be used as stream 560 in the reactor-dissolver 561 and used with the additional carbon dioxide gas stream 563 to alkalinize. Metal carbonates can be converted to alkali metal bicarbonates. The reactor-dissolver 561 can also be provided with a NaOH input stream 562, which can then be converted to alkali metal bicarbonate. NaOH can be supplied from one or both of the electrochemical acidification units 540 and 576 if required.

[0057] Alkali metal formate stream 554 may be a concentrated alkali metal formate solution containing 50% by weight or less water, preferably 40% by weight or less water, more preferably 30% by weight or less water. .. The formate solution stream 554 may be viscous and may contain 0.1% to 30% by weight of alkali metal bicarbonate depending on the water solubility of the alkali metal bicarbonate in the alkali metal formate solution. .. The solution concentrations of the alkali metal formate and the residual alkali metal carbonate can be varied as needed to achieve the desired final residual alkali metal bicarbonate concentration in the alkali metal formate solution. The alkali metal formate stream 554 can then be sent to an alkali metal formate liquid dryer, where residual water can be removed by any suitable means, such as vacuum evaporation. The alkali metal formate may be an alkali metal formate melt containing a small proportion of water in the range of 0.01% by weight to 5% by weight as water. May have alkali metal bicarbonate between 1% and 20% by weight. The alkali metal formate melt stream 566 can then be delivered into the alkali metal formate thermal reactor 568 for high temperature thermal conversion (kali) of the alkali metal formate to alkali metal oxalate. NaOH, sodium hydride, sodium hydride, sodium ethoxide, sodium methoxide, KOH, potassium hydride (KH), potassium ethoxydo (KOEt), potassium methoxide (KOMe), potassium tert-butoxide (KOtBu), etc. Suitable catalysts such as 567 can be added therein before sodium hydride is introduced into the thermal reactor 568. By introducing catalyst 567, the calcination temperature is lowered and the conversion yield of alkali metal formate to alkali metal oxalate is 50% to 99% or more, preferably 70% to 99% or more. Can help improve to the range of. This reaction can also give suitable yields without the need to add catalyst 567. Hydrogen can be the major reaction by-product from the thermal reactor 568, which can be recovered for use in the process. The thermal reactor 568 has different configurations, such as under partial vacuum, under an inert atmosphere such as nitrogen, or by using any suitable gas capable of improving the efficiency of chemical conversion of formate to oxalate. Can be driven by. It may also be useful to add other chemicals to the thermal reactor 568 to obtain a clean fluid purification product. The thermal reactor 568 may be any suitable type of apparatus capable of heating the alkali metal formate to a suitable temperature and controlling the heat or calcination atmosphere. Thermal reactors 568 include tunnel furnaces, rotary kilns, high temperature spray dryers, high temperature rotating drum / flaker units, fluidized bed reactors, and other commercially available calciners and designs that may be commercially available. Can be mentioned. Can be collected. The thermal reactor 568 has different configurations, such as under partial vacuum, under an inert atmosphere such as nitrogen, or by using any suitable gas capable of improving the efficiency of chemical conversion of formate to oxalate. Can be driven by. It may also be useful to add other chemicals to the thermal reactor 568 to obtain a clean fluid purification product. The thermal reactor 568 may be any suitable type of apparatus capable of heating the alkali metal formate to a suitable temperature and controlling the heat or calcination atmosphere. Thermal reactors 568 include tunnel furnaces, rotary kilns, high temperature spray dryers, high temperature rotating drum / flaker units, fluidized bed reactors, and other commercially available calciners and designs that may be commercially available. Can be mentioned. Can be collected. The thermal reactor 568 has different configurations, such as under partial vacuum, under an inert atmosphere such as nitrogen, or by using any suitable gas capable of improving the efficiency of chemical conversion of formate to oxalate. Can be driven by. It may also be useful to add other chemicals to the thermal reactor 568 to obtain a clean fluid purification product. The thermal reactor 568 may be any suitable type of apparatus capable of heating the alkali metal formate to a suitable temperature and controlling the heat or calcination atmosphere. Thermal reactors 568 include tunnel furnaces, rotary kilns, high temperature spray dryers, high temperature rotating drum / flaker units, fluidized bed reactors, and other commercially available calciners and designs that may be commercially available. Can be mentioned.

[0058] The alkali metal oxalate production stream 570 discharged from the thermal reactor 568 can be cooled and sent to the oxalate solution solubilizer 572, where the solid alkali metal oxalate is dissolved in water. It can be filtered by a variety of available methods to remove insoluble material and give a clear filtration product solution free of suspended solids. Alkali metal oxalate products may contain alkali metal carbonates and / or alkali metal bicarbonates as one or more by-products of scorch. Alkali metal oxalate-alkali metal bicarbonate solution may not require more energy or water vapor for evaporation of water in the evaporator-crystallizer 576, as the solution can be sufficiently concentrated. There is sex.

[0059] The alkali metal oxalate solution stream 574 can then be sent to the electrochemically acidified cell 576, where the alkali metal oxalate solution is sent through the ion exchange compartment of the cell to oxalate. It can be converted to a stream 580 and a carbon dioxide stream 579, which can be produced by acidification of the alkali metal carbonate present in the alkali metal oxalate stream 574. The electrochemically acidified cell 576 can use the same chemistries and configurations as the electrochemically acidified cell 540, producing the co-products oxygen and hydrogen, as well as NaOH as the stream 578.

[0060] Referring to FIG. 6, in another embodiment, according to one aspect of the invention, a dicarboxylic acid such as oxalic acid is produced, starting from the electrochemical formation of formate with carbon dioxide. The system 600 for doing so is shown. In addition to producing another co-product, system 600 can provide another system for producing the oxalic acid produced by systems 100, 105 of FIGS. 1A and 1B.

[0061] System 600 may include an electrochemical cell 610. Electrochemical cell 610 is CO₂Electrochemical reduction of carbon dioxide was carried out using an alkali metal carbonate cathode supply stream that can be formed from the reaction of sodium hydroxide and hydrochloric acid (HCl) (which was purified) as the anode solution. When using an electrochemical unit (which can be produced in an electrochemical unit 670 where a NaCl solution input and supply material can be used), it can be operated to be produced together with chlorine gas as an anode product.

[0062] Alkali metal formate can be sent to thermal reactor 620. The alkali metal formate can be separated from the bicarbonate present in the cathode solution by various means as described in FIG. 5 to provide a suitable feed stream to the thermal reactor 620. The thermal reactor 620 uses alkali metal hydroxides (eg, KOH, NaOH) or other catalysts to perform thermal intermolecular condensation reactions, i.e. CC (carbon-carbon bond) coupling reactions, and alkali metal oxalic acid. Salt can be produced.

[0063] The alkali metal oxalate from the thermal reactor 620 can then be dissolved in water and then sent to the electrochemical acidifying electrolytic cell 630. The electrochemical acidifying electrolytic cell 630 can generate a dicarboxylic acid such as oxalic acid and NaOH together with oxygen and hydrogen by-products. The electrochemical acidifying electrolytic cell 630 may be a membrane-based unit containing at least three regions, an anode region, one or more central ion exchange regions, and a cathode region. Alkali metal oxalate can be sent through the central ion exchange region, where the alkali metal ions can be substituted with protons, where the substituted alkali metal ions are sent through the adjacent membrane into the cathode region. Form NaOH. The anodic reaction can produce chlorine gas when using the HCl feed stream from the electrochemical unit 670. Alternatively, the anodic reaction can produce oxygen and hydrogen gases using different acids such as sulfuric acid. Alternatively, the electrochemical acidifying electrolytic cell 630 may be an electrochemical electrodialysis unit that uses a bipolar membrane to produce oxalic acid and smaller amounts of hydrogen and NaOH.

[0064] The hydrogen by-products obtained from the electrochemically acidifying electrolytic cell 630 can be used as a fuel for the production distribution in another embodiment, or hydrogen can be used as in the chemical hydrogenation process. Can be used in. The chemical hydrogenation process is, for example, hydrogenation of an oxalic acid solution capable of forming high-purity monoethylene glycol (MEG) or of oxalic acid such as dimethyl oxalate (DMO) and diethyl oxalate (DEO). It may be hydrogenation of the ester.

[0065] The aqueous NaOH solution from the electrochemically acidifying electrolytic cell 630 can be sent to the evaporator 640. The evaporator 640 can evaporate water from the NaOH aqueous solution product using steam or another heat source and convert it into a concentrated aqueous solution and / or solid having a moisture content of 5% or less. NaOH is CO in reactor 680₂Can react with the alkali metal bicarbonate solution to form carbon dioxide, which can be sent to the cathode solution compartment in the electrochemical cell 610. NaOH can also be transformed into a solid for use as a catalyst in the thermal reactor 620.

[0066] The electrochemical unit 670 may be an electrochemically acidified electrolytic cell of the type such as the electrochemically acidified electrolytic cell 630, wherein the purified NaCl brine solution is sent into the ion exchange compartment. It can be acidified to generate an HCl-forming stream in the cathode cell and co-produce NaOH and hydrogen. Sulfuric acid can be used as the anode solution to generate oxygen from the oxidation of water. Brine purification and recirculation unit 660 produces purified brine suitable for use in electrochemical unit 670, using NaCl solid feed material and various refined chemicals as needed to produce purified brine. Can be made to. The electrochemical unit 670 may include other types of electrochemical units, such as electrodialysis units that can use bipolar membranes, and any other suitable type of electrolytic cell capable of producing HCl. it can.

[0067] In other embodiments, the system 600 uses chlorine and NaOH produced from the electrochemical unit 670 and the electrochemical acidifying electrolytic cell 630 as co-products from the system, alkali metal hypochlorite. (For example, NaOCl) can also be generated. Alternatively, chlorine can be reacted with an organic substance to produce various chlorinated chemical products such as ethylene dichloride (EDC). MOH can be another product of the process, or it can be converted to alkali metal carbonates or alkali metal bicarbonates, thereby converting additional carbon dioxide into useful chemicals.

[0068] In another embodiment, the alkali metal formate produced in the electrolytic cell 610 is bypassed the thermal reactor 620 and sent directly to the electrochemical acidifying electrolytic cell 630 to directly produce the formic acid product. be able to. Formic acid is the final product, or can be converted to other suitable chemicals such as methyl formate, or reacted with various salts to produce alkali metal formates such as calcium formate. Methyl formate can also be converted by reaction with amines to produce amides such as formamide or dimethylformamide.

[0069] In another aspect, the electrochemical unit 670 may include a two-compartment cell having an anode compartment and a cathode compartment separated by a separator or membrane. In this embodiment, NaCl can be supplied to the anolyte compartment to produce chlorine, and sodium hydroxide and hydrogen are produced in the cathode compartment.

[0070] With reference to FIG. 7, in another aspect, according to one aspect of the invention, a carboxylic acid such as formic acid is produced, starting with the electrochemical formation of formate with carbon dioxide. System 700 for is shown. The system uses three compartments of electrochemical cells, including an anode compartment, a central ion exchange compartment, and a catholyte compartment.

[0071] In the electrochemical cell 701, two ions which are preferably cationic ion exchange type films forming a cathode liquid region or a cathode compartment 704, an anode liquid region or an anode compartment 712, and a central ion exchange compartment 714. Permeable separators 706 and 708 can be included. An anodic solution feed stream 726 containing sulfuric acid electrolyte can be introduced into the anodic solution compartment 712 of the electrochemical cell 701, where water is oxygenated and H in the anodic 710 in the anodic solution compartment 712.⁺Can be oxidized to ions. The anodic fluid flow 716 can be discharged from the anodic fluid compartment 712 and introduced into the anodic fluid dissociator 718, where the oxygen gas 720 can be discharged as an electrochemical cell anodic fluid by-product. The gas-separated solution stream 722 can be expelled from the dissociator 718 and the water stream 724 can be added to the solution stream 722 to maintain water levels within the anolyte system loop. Water loss in the anolyte system loop can be transferred into the ion exchange compartment 714 through the cationic ion exchange membrane 708 by the water consumed from the anodic oxidation reaction and an electrochemical transfer process called electroosmotic resistance. There is H⁺It may be due to the water of crystallization that associates with the ions. The anode 710 can contain any suitable stable electrode material suitable for oxidation of water in the sulfuric acid electrolyte, which can have a long operating life and be stable. The anode can include a metal or non-metal with an electrocatalyst coating for efficient oxidation of water. The anode can also optionally include a gas diffusion electrode (GDE), which does not produce oxygen, but water and H, such as by introducing excess hydrogen into the anode GDE.⁺It can be operated in other electrochemical anode reactions capable of forming ions, which can include suitable catalysts for the hydrogen oxidation reaction at the anode. The GDE anodic reaction with water may be on the order of about 0.100 volts, which is much lower than the half-cell potential for oxidation of water, which is 1.23 volts. It provides a cell operating potential, which corresponds to a much lower operating cost for the electrochemical cell 701. The anodic fluid circulation loop 726 is used to cool the pump (not shown) and the flow 726 before it is introduced into the anolyte compartment 712 to control the temperature of the electrolyte in the anodic fluid compartment 712. A heat exchanger (not shown) can be included.

[0072] In the electrochemical cell 701, a cathode liquid region or compartment 704 having a mounted cathode 702, which may be a metal or non-metal electrode having an active carbon dioxide electrocatalyst layer on the front side facing the membrane 706, is provided. Can be given. The cathode 702 can include the high surface area cathode structure shown and described in FIG. 3 so that it can be efficient in the electrochemical reduction of carbon dioxide to formate. For example, potassium bicarbonate and dissolved CO₂, And in some cases CO₂A flow of electrolyte stream 748 at a suitable flow rate containing a pH controlled electrolyte containing microbubbles can be introduced into the cathode solution compartment 704, where the cathode 702 is subjected to an electrochemical reduction reaction at a suitable potential. The cathode can be efficiently produced in. H introduced into the cathode fluid compartment 704 through the adjacent cation exchange membrane 706⁺The bicarbonate electrolyte is acidified by ions so that CO is given in Reaction 17.₂And in addition to producing water, the pH of the cathode fluid stream within the cathode fluid compartment 704 can be varied. Any other electrode competition reaction at the cathode, such as the formation of hydrogen from the water reduction reaction 4, can be formed and can be present in the cathode solution electrolyte. K discharged from the ion exchange compartment 714 through the cationic ion exchange membrane 706 shown in FIG.⁺The co-movement of ions can supply potassium cations during the catholyte reaction. H⁺Ion and K⁺The ratio of ions can determine the pH of the electrolyte solution flowing through the cathode solution compartment 704. H⁺/ K⁺The ratio can be controlled by controlling the rate of flow of the sodium formate solution 714 into the ion exchange compartment 714.

[0073] Cathodic compartmentalized flow 730 is then sent through the vicinity of pH monitoring sensor 731 (and temperature sensor: not shown) that can be used to monitor and control the pH value of the cathodic fluid flow, and then Can be introduced into the cathodic dissociator 732, where mainly excess CO₂And hydrogen, as well as various gases such as other cathode reduction side reaction gas products such as ethylene, CO, methane, etc., can be separated from the solution stream as a stream 734. These gases can be separated, recovered and recirculated to the process, if desired.

[0074] The catholyte dissociator flow 738 can then be recirculated back to the catholyte compartment 704. CO as flow 740₂, And KHCO to be weighed in₃A solution stream 742 is introduced into the recirculation stream 738 and the resulting stream is then fed through the vicinity of a pH monitoring sensor 743 that measures and controls the pH of the flow mixture 744. The flow 744 is then introduced into the inlet of the circulation pump 746, drained as a solution flow flow 748 and introduced into the cathode liquid compartment 704. CO to be injected₂The flow of the stream is thereby sufficient for the reduction reaction of the cathode 702 in the cathode fluid compartment 704, preferably in excess of CO.₂Is like being given. CO in the electrolyte solution flow introduced into the cathode solution compartment 704₂Fine bubbles are formed, and CO is dissolved in the electrolytic solution.₂CO to form₂Can be injected. KHCO introduced into the cathode fluid flow 738₃The metered feed stream 742 is supplied at a rate or flow rate into the stream 738 sufficient to help maintain the solution stream 744 as a stream 748 in the desired pH range prior to introduction into the cathodic compartment 704. The pH range may be in the range of about 2-12, more preferably in the range of about 3-11, even more preferably in the range of about 4-10. The operating pH range can be determined by the electrochemical properties of the selected cathode electrocatalyst material and the composition of the electrolyte used in the cathode fluid flow. In addition, a heat exchanger (not shown) is used after the circulation pump 746 to bring the cathode solution to a range of about -5 ° C to 80 ° C, more preferably about 0 ° C to 70 ° C, more preferably. It can be cooled to an operating range of about 5 ° C to 60 ° C. The temperature of the cathode solution and the composition of the electrolyte are determined by the CO in the cathode solution electrolyte solution.₂May affect the solubility of.

[0075] The cathode solution dissociator 732 uses potassium formate (K-formate) as residual potassium bicarbonate (KHCO).₃) Can be given with potassium formate production logistics 736, which is from potassium formate to KHCO₃Can be sent to the K-formate-bicarbonate separation unit 750, which can be used to separate. The separation unit can evaporate water from the solution and use the relative solubility of the chemical components in the aqueous solution to efficiently perform the separation, an evaporator-crystallizer, a flow-down membrane evaporator, or steam or It may be any suitable commercial device that uses other energy heating sources and vacuum.

[0076] Separation unit 750 is the outlet KHCO₃Solution-producing Logistics 742 can be generated, which can be metered into the catholyte recirculating solution stream 738 for pH control. The concentration of the solution stream is in the range of about 5% to 60% by weight, or more preferably 10% by weight to 55% by weight, in order to control the amount of water input into the cathode solution electrolyte recirculation flow 748. Can be a range. Separation unit 750 has a water vapor discharge stream 752 from evaporation and, in some cases, excess KHCO.₃A stream 754 can be provided, which can be used to equilibrate the water or potassium compounds in the system if required and can be added to the system as needed.

The separation unit 750 is also KHCO at a level in the range of about 0.1% to 10% by weight, preferably in the range of about 0.1% to 5% by weight, more preferably in the range of about 0.1% to 1% by weight.₃It is also possible to provide a K-formate production stream 756 containing a potassium formate solution that may contain. K-formate production logistics 756 has a concentration of about 5% to 80% by weight, more preferably 10% to 60% by weight, and most preferably 10% to 50% by weight as potassium formate. You can do it.

[0078] The K-formate product distribution 756 can be metered into the ion exchange compartment 714 in the electrochemical cell 701, where it is acidified to produce the formate solution product distribution 728. The flow velocity of the solution flow 756 and the applied operating current of the electrochemical cell 701, which is H passing through the cationic ion exchange membrane 708 and into the ion exchange compartment 714.⁺(May be proportional to ions) determines the amount of potassium removed from potassium formate in solution when producing formic acid product 728. Formic acid product 728 can then be further treated and purified as needed to the final formic acid product, converted to other formate products as a salt, or used as an intermediate in a chemical process. ..

[0079] In another embodiment, as shown in FIG. 11, the formic acid-producing logistics 728 can be used as a hydrogen storage source in an energy storage system for use in supplying power to the power grid during off-peak periods. ..

[0080] Referring to FIG. 8, a system 800 for producing a carboxylic acid, such as formic acid, is shown according to one aspect of the invention, which begins with the electrochemical formation of formate with carbon dioxide. Has been done. System 800 may be similar to System 700, but here the anolyte compartment can generate halogens such as chlorine when a hydrogen halide supply stream such as HCl is used as the anodic solution feed stream. .. In system 800, the anodic solution feed stream 826 contains HCl, which can be supplied into the anodic solution compartment 812 containing the anodic acid 810, which may be suitable for oxidizing HCl to chlorine. The anodic solution compartment outlet flow 816 can then be introduced into the anodic solution dissociator 818, where chlorine is separated from the anodic solution solution stream. If the volume of water in the anodic solution is not in equilibrium, an overflow stream 819 can be used if desired, which can then be recirculated to the system. The recirculation flow 822 from the anodic solution dissociator 818 includes an input water stream 824 that is added to supply water to the anodic solution stream as needed, and chlorine ions that oxidize to chlorine at the anodic 810 in the anodic solution compartment. Can be provided with an HCl supply stream 825 that is metered in to supply. The mixed feed stream 826 can then be introduced into the anodic fluid compartment 812.

[0081] The anodic solution feed stream 826 can also contain a portion of the electrolyte solution as sulfuric acid added as the stream 827, which can function as a supporting electrolyte solution. The amount of sulfuric acid may range from about 0.5% to 20% by weight in the anolyte solution stream 826. In addition to being a supporting electrolyte, sulfuric acid allows the volume or rate of chlorine production from the anolyte compartment 812 to vary, and both chlorine and oxygen production are metered into the anolyte compartment 812. It is proportional to the HCl. Thus, the mass or molar ratios of chlorine to formic acid from System 800 can be varied as needed to meet the requirements of the process used. The molar ratio of formic acid product to chlorine co-product can vary from about 100: 1 to 1: 1 or more preferably in the range of 90: 1 to 1: 0.9.

[0082] The HCl feed stream 825 may be an aqueous solution, in the range of about 5% to 36% by weight as HCl, more preferably in the range of about 10% to 30% by weight as HCl, most preferably about 10% by weight as HCl. It may be in the range of% by weight to 20% by weight. The operating temperature of the anode solution may be in the range of 5 ° C to 80 ° C, more preferably in the range of 10 ° C to 60 ° C. The optimum operating temperature can be selected according to the material composition of the anode 810, where by using some metals such as titanium grade including Pd such as ASTM grades 7, 11, and 17 as substrates. It provides good resistance to HCl, which can provide an upper limit for operating temperature.

[0083] In other embodiments, in the anodic fluid stream 826 introduced into the anodic fluid compartment 812, where bromine may be sought as a co-product from the electrochemical formate system 800. Weigh in HBr. It is possible to ensure that the supported sulfuric acid electrolyte is used to efficiently produce bromine while maintaining a low concentration of tribromide in the anolyte solution. The molar ratio of formic acid product to bromine co-product can vary from about 100: 1 to 1: 1 or more preferably in the range of 90: 1 to 1: 0.9.

[0084] With reference to FIG. 9, in another embodiment, the structure of carbon dioxide, a thermal reactor for converting formate to oxalate, and a trisection electrochemical cell 901 according to one aspect of the invention. A system 900 for producing oxalic acid solution products and oxygen by-products is shown in use. System 900 can use a three-compartment electrochemical cell 901 that includes an anode compartment, a central ion exchange compartment, and a cathode fluid compartment.

[0085] In the electrochemical cell 901, there are two cathode liquid regions or cathode compartments 904, an anode liquid region or anode compartment 912, and preferably a cationic ion exchange type membrane, forming a central ion exchange compartment 914. Ion permeable separators 906 and 908 can be included. An anodic solution feed stream 926 containing sulfuric acid electrolyte can be introduced into the anodic solution compartment 912 of the electrochemical cell 901, where water is oxygenated and H at the anodic 910 in the anodic compartment 912.⁺Can be oxidized to ions. The anodic solution product distribution 916 is discharged from the anodic solution compartment 912, which can be introduced into the anodic solution dissociator 918 where the oxygen gas 920 can be discharged as an electrochemical cell anodic solution co-product. A gas-separated solution stream 922 can be expelled from the dissociator 918 and a water stream 924 can be added to the solution stream 922 to maintain water levels within the anolyte system loop. Water loss within the anolyte system loop can be transferred through the cation exchange membrane 908 into the ion exchange compartment 914 by the water consumed from the anodic oxidation reaction and an electrochemical transfer process called electroosmotic resistance. There is H⁺It may be due to the loss of bound water that associates with the ions. The anode 910 can contain any suitable stable electrode material suitable for oxidation of water in the sulfuric acid electrolyte, which can have a long operating life and be stable. The anode can include a metal or non-metal with an electrocatalyst coating for efficient oxidation of water. The anode can also optionally include a gas diffusion electrode (GDE), which does not produce oxygen, but water and H, such as by introducing excess hydrogen into the anode GDE.⁺It can be operated in other electrochemical anode reactions capable of forming ions, which can include suitable catalysts for the hydrogen oxidation reaction at the anode. The GDE anodic reaction with water may be on the order of about 0.100 volts, which is much lower than the half-cell potential for oxidation of water, which is 1.23 volts. It provides a cell operating potential, which corresponds to a much lower operating cost for the electrochemical cell 901. The anodic fluid circulation loop 926 includes a pump (not shown) and a flow 926 for cooling the anolyte compartment 912 before being introduced into the anolyte compartment 912 to control the temperature of the electrolyte in the anodic fluid compartment 912. A heat exchanger (not shown) can be included.

[0086] In the electrochemical cell 901, a cathode liquid region or compartment 904 having a mounted cathode 902, which may be a metal or non-metal electrode having an active carbon dioxide electrocatalyst layer on the front side facing the film 706, is provided. Can be given. The cathode 702 can include the high surface area cathode structure shown and described in FIG. 3 so that it can be efficient in the electrochemical reduction of carbon dioxide to formate. For example, potassium bicarbonate and dissolved CO₂, And in some cases CO₂A flow of electrolyte stream 948 at a suitable flow rate containing a pH controlled electrolyte containing microbubbles can be introduced into the cathode solution compartment 904, where the cathode 902 is subjected to an electrochemical reduction reaction at a suitable potential. The cathode can be efficiently produced in. H introduced into the cathode solution compartment 904 through the adjacent cation ion exchange membrane 906⁺Ions acidify the bicarbonate electrolyte so that CO is given in Reaction 17.₂And in addition to producing water, the pH of the cathodic fluid stream in the cathodic fluid compartment 904 can be varied. Any other electrode competition reaction at the cathode, such as the formation of hydrogen from the water reduction reaction 4, can be formed and can be present in the cathode solution electrolyte. K discharged from the ion exchange compartment 914 through the cationic ion exchange membrane 906 shown in FIG.⁺The co-movement of ions can supply potassium cations during the catholyte reaction. H⁺Ion and K⁺The ratio of ions can determine the pH of the electrolyte solution flowing through the cathode solution compartment 904. H⁺/ K⁺The ratio can be controlled by controlling the rate of flow of sodium oxalate solution 974 into the ion exchange compartment 914.

[0087] Cathodic compartmentalized flow 930 is then sent through the vicinity of a pH monitoring sensor 931 (and temperature sensor: not shown) that can be used to monitor and control the pH value of the cathodic fluid flow, and then Can be introduced into the cathodic dissociator 932, where mainly excess CO₂And hydrogen, as well as various gases such as other cathode reduction side reaction gas products such as ethylene, CO, methane, etc., can be separated from the solution stream as a stream 934. These gases can be separated, recovered and recirculated to the process, if desired.

The catholyte dissociator flow 938 can then be recirculated back to the catholyte compartment 904. CO as flow 940₂, And KHCO to be weighed in₃The solution stream 942 is introduced into the recirculation stream 938 and the resulting stream is then fed through the vicinity of a pH monitoring sensor 943 that measures and controls the pH of the flow mixture 944. The flow 944 is then introduced into the inlet of the circulation pump 946, discharged as a solution flow flow 948, and introduced into the cathode liquid compartment 904. CO to be injected₂The flow of the stream is thereby sufficient for the reduction reaction of the cathode 902 in the cathode fluid compartment 904, preferably in excess of CO.₂Is like being given. CO in the electrolyte solution flow introduced into the cathode solution compartment 904₂Fine bubbles are formed, and CO is dissolved in the electrolytic solution.₂CO to form₂Can be injected. KHCO introduced in cathode fluid flow 938₃The metered feed stream 942 supplies the solution stream 944 as a stream 948 at a rate or flow rate into the stream 938 sufficient to help maintain the desired pH range prior to introduction into the cathodic compartment 904. The pH range may be in the range of about 2-12, more preferably in the range of about 3-11, even more preferably in the range of about 4-10. The operating pH range can be determined by the electrochemical properties of the selected cathode electrocatalyst material and the composition of the electrolyte used in the cathode fluid flow. In addition, a heat exchanger (not shown) is used after the circulation pump 946 to bring the cathode solution solution in the range of about -5 ° C to 80 ° C, more preferably about 0 ° C to 70 ° C, more preferably. It can be cooled to an operating range of about 5 ° C to 60 ° C. The temperature of the cathode solution 904 and the composition of the electrolyte are determined by the CO in the cathode solution electrolyte solution.₂May affect the solubility of. CO₂Solubility can be increased by reducing the electrolyte concentration, operating at a lower temperature, and operating the electrochemical cell 901 at a higher pressure. Alternatively, the GDE electrode is a CO in the electrode structure.₂Operated at higher partial pressures, CO in solution electrolyte₂The formate cell 901 system has a higher current density (which is CO) because it may not be as limited as the solubility of₂A cathode 902 with GDE-based electrodes can be used which can be operated at (can be on the order of about 33 mM).

[0089] Cathode dissociator 932 contains potassium formate (K-formate) as residual potassium bicarbonate (KHCO).₃) Can be given with potassium formate production logistics 936, which is KHCO from potassium formate solution₃Can be sent to the K-formate-bicarbonate separation unit 950, which can be used to separate as a solid product. The separation unit evaporates water from the potassium formate solution and uses the relative solubility of the chemicals in the aqueous solution to KHCO from potassium formate.₃It may be an evaporator-crystallizer, a run-down membrane evaporator, or any suitable commercial device using steam or other energy heating sources and vacuum capable of efficient separation.

Separation unit 950 is a KHCO with some residual potassium formate.₃KHCO at the outlet that may contain solids / crystals₃A solution-producing logistics 980 can be given. KHCO to be separated₃The amount of residual potassium formate in the solid is about 0.1% to 10% by weight or less, more preferably about 0.1% to 5% by weight or less, and most preferably 0.1% to 2% by weight as potassium formate. Or less than that. KHCO₃KHCO by solid / liquid separation methods such as centrifugation, vacuum filter filtration, etc. used with the methods used to wash / rinse potassium formate from crystals.₃The amount of potassium formate excreted with it can be determined by weight%. Separation unit 950 has a water vapor discharge stream 952 from evaporation and, in some cases, excess KHCO.₃A stream 954 can be provided, which can be used to equilibrate the water or potassium compounds in the system if required and can be added to the system as needed.

[0091] KHCO₃The solid / crystallized logistics 980 can then be sent to the carbonate reaction / dilution vessel 976, where water 941 is added and KHCO₃Dissolve solid 980. In addition, K-oxalate-K₂CO₃K from unit 970₂CO₃Flow 972 is also introduced into container 976. CO₂Gas 978 can be injected into container 976 to completely convert potassium carbonate to potassium bicarbonate according to reaction (14b).

[0092] Flow 942 can be expelled from vessel 976, which can be metered into catholyte recirculating solution stream 938 to control pH in the catholyte loop of electrochemical cell 901. The concentration of solution flow 942 is KHCO to control the total amount of water input into the cathode solution electrolyte recirculation flow 948.₃As in the range of about 5% to 60% by weight, or more preferably KHCO₃It can be in the range of 10% by weight to 55% by weight.

The separation unit 950 is in the range of about 0.1% to 10% by weight or less, preferably from about 0.1% to 5% by weight or less, more preferably from about 0.1% to 1% by weight. Range level KHCO₃A K-formate production stream 956 containing a potassium formate solution which may contain. The K-formate production stream can preferably have a concentration in the range of about 90% to 99.9% by weight as potassium formate, more preferably 98% to 99.9% by weight as potassium formate, with the rest being water. .. Most preferably, the potassium formate stream 956 from the separation unit 950 can contain as little water as possible, which is essentially a melt of potassium formate having a melting point of about 167 ° C. ..

[0094] Preferably, the K-formate production stream 956 can be sent to the thermal reactor 958 as a potassium formate melt, where oxalate at a high conversion rate under specific temperature, atmospheric gas, and reaction time conditions. It can be converted to potassium acid. The thermal reactor 958 can be operated in the range of about 100 to 550 ° C, more preferably about 200 to 500 ° C. The operating temperature can be determined by the decomposition temperature of the alkali metal formate and the optimum temperature for obtaining the highest yield of the alkali metal oxalate product. The residence time of the reaction at the optimum reaction temperature may range from 5 seconds to several hours, so that the device selected to carry out the reaction gives the heating and cooling rates to obtain the optimum conversion yield. Can be designed. This can include the use of cold rotating metals that can quickly cool the hot thermal products after the thermal reaction time is complete.

[0095] A catalyst capable of improving conversion efficiency and temperature can be used. The catalytic flow 957 can be added to the potassium formate melt 956 in the thermal reactor 958. Suitable catalysts for potassium-based cationic systems include KOH, potassium hydride, potassium hydride, potassium ethoxydo, potassium methoxydo, potassium tert-butoxide, etc., which are thermal reactors. It can be added to potassium formate before it is introduced into 958. By introducing the catalyst 957, the calcination temperature is lowered and the conversion yield of alkali metal formate to alkali metal oxalate is 50% to 99% or more, preferably 70% to 99% or more. Can help improve to the range of. The reaction can also give suitable yields without the need to add catalyst 957. The major reaction by-product from the thermal reactor 958 may be hydrogen 960, which can be recovered for use during the process. The thermal reactor 958 has different configurations, such as under partial vacuum, under an inert atmosphere such as nitrogen, or by using any suitable gas capable of improving the efficiency of chemical conversion of formate to oxalate. Can be driven by. It may also be useful to add other chemicals to the thermal reactor 958 to obtain a clean fluid purification product. The thermal reactor 958 may be any suitable type of apparatus capable of heating the alkali metal formate to a suitable temperature and controlling the heat or calcination atmosphere. Thermal reactors 958 include tunnel furnaces, rotary kilns, high temperature spray dryers, high temperature rotating drum / flaker units, fluidized bed reactors, and other commercially available calciners and designs that may be commercially available. Can be mentioned.

[0096] The K-oxalate production stream 962 discharged from the thermal reactor 958 can be cooled and sent to the K-oxalate dissolution tank 964, where the solid K-oxalate 962 is placed in water. It can be dissolved in and filtered by a variety of available methods to remove insoluble material and a clear filtration product solution free of suspended solids can be obtained. If desired, deionized water stream 966 can be added to unit 964. Alkali metal oxalate products may contain potassium carbonate and / or potassium bicarbonate as one or more by-products of calcination. The solution is a potassium oxalate-alkali metal bicarbonate solution through the flow 968 K-formate-K.₂CO₃It can be sufficiently concentrated so that it does not require more energy or water vapor for evaporation of water at the time it can be delivered onto the separation unit 970.

[0097] K-formate-K₂CO₃The separation unit 970 may be an evaporator-crystallizer that removes water, preferably some of the physical water solubility properties of potassium carbonate that can have much higher water solubility than potassium oxalate. It can be used to precipitate and separate potassium oxalate crystals, which can be redissolved and discharged from the separation unit 970 as K-oxalate solution stream 974. Flow 972 may be a solution of potassium carbonate obtained from the separation unit 970, which can be passed over a carbonate reaction / dilution vessel 976, where CO₂Potassium carbonate can be converted to potassium bicarbonate using stream 978. The potassium bicarbonate stream 942 from the carbonate reaction / dilution vessel 976 can then be metered into the cathode fluid stream 938 of the electrochemical cell 901 for pH control.

[0098] K-formate-K₂CO₃The separation unit 970 can use any other suitable mechanism for separating potassium oxalate from potassium carbonate, including nanofiltration, cooling crystallization, and the like .

[0099] The K-oxalate solution 974 obtained from the separation unit 970 can then be passed over the ion exchange compartment 914 of the electrochemical cell 901 and metered into it, where the oxalic acid production stream. Can be converted to 928. The K-oxalate solution stream 974 can have a concentration range of about 5% to 60% by weight, more preferably about 10% to 50% by weight, as potassium oxalate. The metered flow rate determines the conversion rate of potassium oxalate to oxalic acid, which moves from the ion exchange compartment 914 through the adjacent cationic ion exchange membrane 906 into the cathode solution compartment 904.⁺: K⁺It can affect the ion ratio of cations and can affect the pH of the flowing cathode solution electrolyte. The pH control in the cathode solution compartment 904 is the metered flow rate of K-oxalate solution 974 and KHCO.₃It can be determined by equilibration of a combination of metered flow rates of solution 942. As an option, the flow rate of the K-oxalate solution can be set to a set rate and in the cathodic flow loop of electrochemical cell 901, which can include flows 904, 930, 938, 944, and 948. KHCO with pH sensors 931 and 943 for monitoring and control for pH control₃The metered flow rate of solution 942 can be varied.

[00100] The oxalic acid production stream 928 then implements a smaller electrochemical acidification system as described in Figure 4, removing residual potassium ions to lower levels using ion exchange, if necessary. It can be further purified and concentrated, such as increasing the concentration by removing water by evaporation, and any other suitable treatment. The oxalic acid product can then be further converted to esters such as dimethyl oxalate (DMO), diethyl oxalate (DEO), and dibutyl oxalate (DBO), in one example, which in turn hydrogen. It can be converted to monoethylene glycol using a suitable catalyst in the conversion reactor.

[00101] FIG. 10 shows a further additional aspect applied to the system shown in FIG. 9, where the anodic fluid compartment uses a hydrogen halide feed material such as HCl as the anodic fluid feed stream. Can produce halogens such as chlorine. In system 1000, the anodic solution feed stream 1026 contains HCl, which can be supplied into the anodic solution compartment 1012 containing the anodic acid 1010, which may be suitable for oxidizing HCl to chlorine. The anodic solution compartment outlet stream 1016 can then be introduced into the anodic fluid dissociator 1018, where chlorine is separated from the anodic solution solution stream. If the volume of water in the anodic solution is not in equilibrium, an overflow stream 1019 can be used if desired, which can then be recirculated to the system. The recirculation stream 1022 from the anodic solution dissociator 1018 is charged with deionized water stream 1024, which is added to supply water to the anodic fluid stream as needed, and oxidizes to chloride at the anodic acid 1010 in the anodic fluid compartment. An HCl supply stream 1025, which is metered in to supply chloride ions, can be provided. The mixed feed stream 1026 can then be introduced into the anodic solution compartment 1012.

[00102] The anodic solution feed stream 1026 can also contain a portion of the electrolyte solution as sulfuric acid added as stream 1027, which can function as a supporting electrolyte solution. The amount of sulfuric acid may range from about 0.5% to 20% by weight in the anolyte solution stream 1026. In addition to being a supporting electrolyte, sulfuric acid allows the volume or rate of chlorine production from the anolyte compartment 1012 to vary, and both chlorine and oxygen production are metered into the anolyte compartment 1012. It is proportional to the HCl. Thus, the mass or molar ratios of chlorine to formic acid from System 1000 can be varied as needed to meet the requirements of the process used. The molar ratio of formic acid product to chlorine co-product can vary from about 100: 1 to 1: 1 or more preferably in the range of 90: 1 to 1: 0.9.

[00103] The HCl feed stream 1025 may be an aqueous solution, ranging from about 5% to 36% by weight, more preferably from about 5% to 30% by weight, most preferably from about 10% to 20% by weight. It may be in the range of. The operating temperature of the anode solution may be in the range of 5 ° C to 80 ° C, more preferably in the range of 10 ° C to 60 ° C. The optimum operating temperature can be selected according to the material composition of anode 1010, where by using some metals such as titanium grade including Pd such as ASTM grades 7, 11, and 17 as substrates. It provides good resistance to HCl, which can provide an upper limit on operating temperature due to corrosion by HCl.

[00104] In other embodiments, in the anodic fluid stream 1026 introduced into the anodic fluid compartment 1012, where bromine may be sought as a co-product from the electrochemical formate system 1000. Weigh in HBr. The supported sulfuric acid electrolyte can be used to ensure efficient production of bromine by maintaining a low concentration of tribromide in the anolyte solution. The molar ratio of formic acid product to bromine co-product can vary from about 100: 1 to 1: 1 or more preferably in the range of 90: 1 to 1: 0.9.

[00105] With reference to FIG. 11, a system 1100 using formic acid produced in an electrochemical system for use in an off-peak power energy storage system according to one aspect of the invention is shown. Carbon dioxide can be electrochemically reduced to formic acid products and used in energy storage systems to power the power system in applications such as peak power generation and equalization of power loads. The energy storage system 1100 can use the electrochemical formic acid system described as system 700 in FIG. 7 herein as the electrochemical system 1101, which preferably uses the sun, wind, and / as power. Renewable energy source 1102, which may be another energy source, and CO₂CO in addition to recirculation flow 1126₂Source 1104 is used. Formic acid product 1106 from system 1101 can use catalysts 1110, such as catalysts based on platinum, silver, ruthenium, rhodium, gold, or palladium as their metals, oxides, or alloys. It can be catalytically cracked to hydrogen gas in a cracking reactor 1108 in which one or more catalysts and combinations thereof can be used. Furthermore, other catalyst compositions that may be suitable include transition metals, transition metal alloys, and transition metal oxide compositions. These transition metal catalysts can also contain small amounts of platinum group metals and their oxides in their compositions. The catalyst can be physically placed on a fixed packed bed in the decomposition reactor 1108 or suspended in solution. The decomposition reactor 1108 can be heated and circulated using a pump and pressurized. Decomposition reactor 1108 can also include a plug flow design with a recirculation loop.

[00106] Formic acid reacted in the decomposition reactor 1108 flows as CO as 1114.₂Can be converted to CO₂It can be recirculated back into the recirculation stream 1126 to regenerate formic acid from carbon dioxide. The depleted formic acid solution 1112 from the decomposition reactor 1108 can be recirculated to the system 1100 to produce formic acid. Preferably, the decomposition reactor 1108 can be operated with the catalyst system of choice under conditions that do not require extremely high pressures and temperatures.

[00107] Hydrogen product 1116 from the decomposition reactor 1108 can be pressurized using a compressor (not shown) and sent to the fuel cell system 1118, where an oxidizer such as oxygen is applied. It can be used to convert hydrogen to power 1124. Preferably, the fuel cell system 1118 can be of high temperature solid oxide type, which helps maintain the performance of the fuel cell system 1118, which maintains the load and increases the load, the temperature in the system and A natural gas 1120 supply stream can be used to maintain operating conditions. Fuel cell system 1118 is CO₂An outflow 1122 can be provided, which can be proportional to the amount of natural gas used. CO₂Flow 1122 is CO₂Recirculation Recirculates during the recirculation flow 1126. CO₂Equilibrium with feed stream 1104 and additional CO required for energy storage system 1100₂Can be given.

Electrochemical cell design with gas diffusion electrode: [00108] In the reduction of carbon dioxide, a gas diffusion electrode (GDE) can be used in the electrochemical cell. In the anodic compartment, the anodic reaction of the electrochemical cell oxidizes the hydrogen gas introduced into the anodic GDE and hydrogen ions (H).⁺) Or to form a proton. These protons can then be passed through adjacent cation exchange compartments as shown in FIGS. 3 and 4 or into adjacent ion exchange compartments as shown in FIGS. 7 and 9.

[00109] With reference to FIG. 12, a schematic diagram showing an electrochemical cell using hydrogen GDE for the anodic reaction in producing oxalic acid from the reduction of carbon dioxide according to one aspect of the invention is shown. FIG. 12 shows one of the structures of the hydrogen anode GDE as an electrochemical cell 1200 in cross section, and does not show a part of the internal gas passage in the anode current collector. The electrochemical cell 1200 can include an anode current collector containing an internal gas plenum with a large number of microchannels or grooves connected to the hydrogen GDE to uniformly disperse the hydrogen gas and contact the GDE. Can be done. The microchannel can be extended horizontally or vertically. The gas plenum can also include a current collector with a metal mesh or screen-based structure. Hydrogen gas can preferably be introduced into the anode compartment from the upper inlet port within the anode compartment and flow downward into the plenum as shown, and the depleted hydrogen is then at the bottom of the anode compartment. Can be discharged. Hydrogen can be humidified with solvent vapors used in the anolyte compartment, if desired. The anodic current collector may be of carbon or graphite material or may contain metal if it is resistant to the anodic solution electrolyte reaction and the acidity that may form in the anodic solution. Can be done. Hydrogen can also be operated in a parallel or countercurrent configuration.

[00110] An anodic trickle bed solution distributor or percorator can be placed immediately next to the anodic GDE, where the anodic solution can be introduced at the port at the top of the anodic compartment so that the solution can be evenly distributed. The solution is evenly distributed downward along the length of the trickle bed distributor and drained from the bottom of the anode compartment. The solution is fed at a specific flow rate in the range 0.001-10 liters / min or higher, depending on the size of the electrochemical cell, and the anodic GDE is not completely immersed in the anodic solution due to excessive pressure. Good ionic contact with the anodic GDE can be maintained to move the protons into the anodic solution. The flow rate and pressure of the anolyte flow is 10 ma, with the minimum amount of anolyte solution being able to pass through the GDE into the hydrogen gas plenum inside the anode current collector, with sufficient oxidation of the hydrogen gas in the GDE. /cm²~ 1000ma / cm²Range, or more preferably about 50 ma / cm²~ 500ma / cm²It must be such that a reasonable anode current density can be obtained in the range of. The electrochemical cell 1200 can include an anode and an energy source (not shown) that can be operably connected to the cathode, which powers the anode and cathode to reduce carbon dioxide at the cathode. It is intended to be configured to do so. The anode trickle bed may contain as thin a structure as possible, ranging in thickness from about 0.1 cm to 10 cm, preferably in the range of 0.2 to 5 cm, in order to minimize the IR voltage drop. The anodic trickle bed is non-conductive, corrosion resistant, such as PTFE, polypropylene, PVDF, etc. in the form of a screen or convolution so that the solution is evenly distributed as it passes down the anodic GDE structure. It can be composed of polymer plastic. The inlet and outlet ports of the anolyte compartment are designed so that the anolyte flow distribution is uniform along the cross section of the trickle bed at the top and bottom. Alternatively, the trickle bed material can include conductive carbon and graphite, and some hydrogen GDE catalyst can be included on its surface. GDE can be partially attached to a separator or membrane for improved electrical conduction or contact.

[00111] The separator placed between the anode compartment and the cathode compartment is H.⁺Like a cation membrane, which can conduct cations such as ions through the membrane to the cathode compartment and prevent or reduce the amount of anions returning from the cathode fluid compartment to the anode fluid compartment. It may be a membrane type. Correspondingly, if the electrochemical cell design can use intervening ion exchange compartments as in FIG. 7, the cation membrane allows the cation membrane adjacent to the ion exchange compartment to enter the anode solution compartment. The same reverse movement of the anion can be blocked. The cation membrane selected may preferably be stable to solvents and salts in the electrochemical cell, such as Nafion's trade name perfluorinated sulfonic acid membrane. The separator may also be a microporous separator with micropores in the pore size range of 0.001 to 1 micron, as discussed above, which allows bulk flow of solution or solvent from the cathode solution to the anode solution. Limited or controlled. The bulk flow can be controlled by the flow pressure of the cathode solution solution flowing through the cathode solution compartment.

[00112] The cathodic fluid flow is preferably introduced at the bottom of the cathodic fluid compartment and discharged from the top of the cathodic fluid compartment to facilitate gas removal within the cathodic fluid compartment. The flow rate of the cathode solution can be in the range of 0.01 to 10 liters / minute or more, depending on the dimensions of the electrochemical cell and the operating current density. The cathode fluid compartment uses a high surface area cathode structure to electrochemically reduce carbon dioxide in the cathode fluid to formate. Cathode materials that may be suitable are as described in this application. The operating pressure of the catholyte compartment may be in the range of 0.1-5 psig, or 1-30 psig or higher. The operating pressure may be a function of the flow rate of the cathode fluid and the flow resistance of the high surface area cathode structure used.

[00113] A preferred solvent for the anolyte solution is an aqueous solution containing an electrolyte such as sulfuric acid or a non-oxidizing acid, which is optionally a supporting electrolyte. Organic solvents such as methanol or ethanol that are added to the anode solution in an amount of 50% by weight or less can be used, but may be undesirable if they can interfere with the oxidation of hydrogen at the anode. Salts that may be added to the anolyte electrolyte that may interfere with GDE hydrogen oxidation are not preferred.

[00114] In another aspect, the composition of the electrochemical cell can use an anode and cathode GDE structures that are attached to or in direct contact with a cationic membrane separator.

[00115] In a further embodiment, an ionic conductive material such as a solvent-insoluble resin or an ion exchange material such as an ionomer is used or placed between the anodic and cathodic GDEs. It is possible to provide a conductive ion flow path for ions to move. Alternatively, a gel-type membrane can be used that can include an ion exchange structure or the like capable of retaining an ionic group such as phosphoric acid in the structure. These types of membranes that can be used are used or proposed to be used in phosphate fuels and the like.

[00116] With reference to FIG. 13, hydrogen GDE is used for the anodic reaction and carbon dioxide GDE for the cathodic reaction when producing alkali metal formate from the reduction of carbon dioxide according to one aspect of the invention. A schematic diagram showing the electrochemical cell 1300 is shown. The electrochemical cell 1300 can use the same hydrogen GDE anode as the electrochemical cell 1200 in FIG. 12, but also uses a carbon dioxide reduced GDE cathode structure in the cathode solution compartment. The anodic solution GDE can be operated in the same manner as described in the description of the electrochemical cell 1200 in FIG.

[00117] The cathode GDE operates in the same manner except that it can reduce carbon dioxide to form formate in the cathode GDE. The cathode can be provided with a carbon dioxide internal gas plenum to evenly distribute the carbon dioxide into the cathode GDE.

[00118] A cathodic trickle bed solution distributor can be placed immediately next to the cathodic GDE, where the cathodic solution can be introduced at the top of the cathodic compartment of the cell and the solution down along the cell. Distribute evenly and drain from the bottom of the cathode compartment. Alternatively, the flow can be reversed to make the flow vertical. The solution is fed at a specific flow rate in the range 0.001-10 liters / min or higher, depending on the dimensions of the electrochemical cell, and the cathode GDE is not completely immersed in the cathode solution solution due to excessive pressure. Good ionic contact with the cathode GDE can be maintained to move electrons into the solution during the reduction of carbon dioxide. The flow rate and pressure of the cathode fluid flow is 10 ma, with the minimum amount of cathode fluid solution passing through the GDE into the carbon dioxide gas plenum inside the cathode current collector and the reduction of the carbon dioxide gas in the GDE is sufficient. /cm²~ 1000ma / cm²Range, or more preferably about 50 ma / cm²~ 500ma / cm²It should be such that a reasonable cathode current density in the range of is obtained. The electrochemical cell 1300 can include an anode and an energy source (not shown) that can be operably connected to the cathode, which powers the anode and cathode to reduce carbon dioxide at the cathode. It is intended to be configured to do so. The cathode trickle bed has non-conductive corrosion resistance such as PTFE, polypropylene, PVDF, etc. in the form of a screen or convolution so that the solution is evenly distributed as it passes down the cathode structure. Thin structures made of polymeric plastics that are as thin as possible, ranging in thickness from about 0.1 cm to 10 cm, preferably in the range of 0.2 to 5 cm, can be included. The inlet and outlet ports of the cathode fluid compartment are designed so that the liquid flow distribution is uniform along the cross section of the trickle bed at the top and bottom. The GDE cathode may be able to operate under partially or in some cases fully immersed conditions, adjusting the flow conditions and electrolyte to operate the cathode in this mode. be able to.

[00119] Alternatively, the trickle bed material may include conductive carbon and graphite, or optionally a metal, and may include some cathode GDE catalyst on the surface. Alternatively, the electrochemical cell system 1300 in FIG. 13 can be operated using an oxygen-producing anode system instead of hydrogen GDE as the anode structure as shown in FIGS. 3, 5, 7, and 9.

[00120] Referring to FIG. 14, a schematic diagram showing three different anode GDE structures used in an electrochemical cell in producing alkali metal formate from reduction of carbon dioxide according to one aspect of the invention is shown. There is. FIG. 14A shows a carbon cloth carrier structure containing a thin layer containing a catalyst that can be deposited on a carbon powder substrate by various methods such as spraying or precipitation by a suitable method known in the art. The GDE assembly can then be treated further by using a spray application of PTFE or PVDF emulsion, or by immersing the structure in PTFE or PVDF emulsion, which is then dried to remove the emulsion solvent. Can be done. The assembly is then compressed (under pressure) and heated to a temperature near or near the melting point of PTFE or PVDF, allowing the PTFE or PVDF to flow and combine with various components in the GDE structure to form the microstructure. It is possible to form a three-phase structure that is hydrophobic to the liquid in the portion of the catalyst so that hydrogen can still be sent into the pores for causing the oxidation of hydrogen on the surface of the catalyst. Any possible hydrophobic agent can be used as long as they are not soluble in the solvents used in the anode and cathode solutions of the electrochemical cell. These hydrophobic compounds or agents may differ with respect to the anodic solution GDE and the cathode solution GDE. Hydrophobic to solvents used in the anode solution of electrochemical cells, such as polyethylene and polypropylene waxes, superhydrophobic agents, and other materials such as inorganic oxides, silica-based materials, nitrides, borides, etc. Other potentially hydrophobic agents that may have sex can be used. The content of the hydrophobic material in the anode GDE structure is 1% to 80%, preferably 1% to 80% by weight or volume in the GDE structure in order to obtain the required non-wetting and anode GDE performance characteristics. It may be in the range of about 5% to 50%.

[00121] The hydrogen oxidation catalyst used in the anode solution GDE can include noble metals and noble metal oxides and mixtures thereof, such as platinum, palladium, gold, ruthenium, iridium, and silver, and alloys and mixtures thereof. .. The concentration of GDE catalysts such as platinum is 0.5 mg / cm with respect to platinum on the carbon powder carrier.²It's like being economical. The catalyst concentration is approximately 0.01-20 mg / cm for many of these noble metal catalysts.²Range, more preferably 0.1-5 mg / cm²It may be in the range of. More catalysts can be used in the composition if lower cost catalyst materials are available. The carrier for the catalyst may be high surface carbon or graphene, conductive nitrides, carbon nanotubes, conductive titanium suboxides such as Ti.₄O₇And Ti₂It may be another conductive material such as O. The catalyst can be applied by various methods such as electroplating, chemical reduction, chemical precipitation, and chemical vapor deposition. Numerous GDEs have been described in the literature and are commercially available, which can be used as anode GDEs if they may have the suitable hydrophobicity and catalytic activity required for this process.

[00122] FIG. 14B shows the same structure as FIG. 14A, except that it is provided with an additional secondary phase containing carbon powder with a hydrophobic binder / filler in its composition. [00123] FIG. 14C is provided with a thinner metal mesh within the carbon cloth carrier that can provide the structure with mechanical stability and also provide a better conductive structure. The GDE structure shown in Figure 14B is shown, except that the GDE can be operated at high current densities. The metal may be nickel, silver, or any other metal or alloy that is corrosion resistant to anode operating conditions.

[00124] In another embodiment, if further elimination of solvent flow is required, the separator or membrane is attached to the anode GDE structure on one or both surfaces of the anode and / or cathode GDE. Can be made to. In other embodiments, Nafion (perfluorinated sulfonic acid) -based solutions can also be used in the GDE structure to provide additional binding and provide an ionic conductive medium within the GDE structure. Other ionic monomers similar to Nafion can be used, such as ion exchange resin materials and non-halogenated ionomers such as sulfonated polystyrene, sulfonated divinylbenzene and the like. In addition, the anode GDE is also post-treated with a spray to add additional hydrophobic materials or compounds, such as various commercially available superhydrophobic materials, to the internal and external surfaces of the GDE. Can be done.

[00125] Referring to FIG. 15, a schematic diagram showing three different cathode GDE structures 1500 used in an electrochemical cell in producing alkali metal formate from reduction of carbon dioxide according to one aspect of the invention is shown. ing. Figures 15A, 15B, and 15C show high hydrogen overvoltage metals such as indium, tin, bismuth, etc., which are suitable electrolytic catalysts for the reduction of carbon dioxide, for example, for the reduction of carbon dioxide to formate. Has the same relative corresponding structures as in FIGS. 14A, 14B, and 14C, except that can be included. Preferred metal catalysts include, for example, indium, tin, bismuth, lead, silver, gold, zinc as a coating of single and multiple compositions deposited on various metals, carbons, or other conductive carriers. , And cadmium (including these binary and ternary alloys, intermetallic compounds, and combinations). Other suitable catalysts may further include other transition metals such as copper, cobalt, manganese, vanadium, and nickel, which are the preferred metals already mentioned such as indium, tin, and silver. It can be mixed and alloyed with catalysts. Preferred carbon dioxide reduction products such as CO or formate may determine the catalyst of choice for use in GDE. For example, silver-based catalysts may be preferred for efficiently converting carbon dioxide to CO, while indium-tin alloys may be most preferred for reducing carbon dioxide to formate. Most importantly, the stability of the catalyst against the cathode reaction is the key to providing a long-lived cathode for the electrochemical process.

[00126] The catalyst layer may be a high surface area powder containing a metal deposited on a carbon or conductive ceramic substrate, or in the range of 5% to 90% by weight as one or more metals. A composition using a high surface area metal powder which may have a suitable metal composition can be included. Three-dimensional cathode CO using hydrophobic PTFE or other described hydrophobic and ionic conductive polymer material₂It can help provide binding in forming the reduced GDE structure. High surface area metal mesh or cloth structures, or metallized carbon or polymer materials can be used instead of carbon cloth, which may be non-woven or sintered. In addition, a small proportion of the monomer can be added to the GDE composition which can be polymerized to form a rubber or elastomer type structure that does not significantly reduce the conductivity and ionic conductivity of the GDE structure.

[00127] Referring to FIG. 16, an electrochemical cell 1600 using a hydrogen GDE and a weir-type solution partitioning system for an anodic reaction in producing alkali metal formate from carbon dioxide reduction according to one aspect of the invention. A schematic diagram is shown. The electrochemical cell 1600 can include different arrangements of the anolyte solution inlet and anolyte solution outlet ports as compared to the electrochemical cell 1200. Hydrogen can also be operated in a parallel or countercurrent configuration. The electrochemical cell 1600 can include an anode and an energy source (not shown) that can be operably connected to the cathode, which powers the anode and cathode to reduce carbon dioxide at the cathode. It is intended to be configured to.

[00128] Referring to FIG. 17, electrochemical using hydrogen GDE for the anodic reaction and carbon dioxide GDE for the cathodic reaction in producing alkali metal formate from the reduction of carbon dioxide according to one aspect of the invention. A schematic diagram showing cell 1700 and showing a dam-type solution distribution system is shown. The electrochemical cell 1700 includes a dam-type anode liquid flow and cathodic liquid flow solution distributor that uniformly distributes the anode liquid and cathode liquid solutions to the anode liquid and cathode liquid trickle bed distributors, respectively. The electrochemical cell 1700 also shows a different arrangement of solution inlet and outlet flow ports for the anodic and cathodic solutions compared to the electrochemical cell 1300. The electrochemical cell 1700 can include an anode and an energy source (not shown) that can be operably connected to the cathode, which powers the anode and cathode to reduce carbon dioxide at the cathode. It is intended to be configured to.

[00129] In another embodiment, the cathode carbon dioxide GDE structure may be compressed and thermally bonded to a thin porous sheet and then metal or carbon based material or a combination thereof, as shown in FIGS. 12-17. A high surface area metal powder catalytic substrate mixed with a hydrophobic binder that can be further attached to the GDE carrier structure shown can be included. The proportion of the hydrophobic agent in the metal powder catalyst may be in the range of 2% by weight to 95% by weight, more preferably 5% by weight to 80% by weight. Metal powder catalysts can include metals suitable for reducing carbon dioxide to formate and their alloys, such as indium and tin and their alloys. The metal particles can include a plurality of electrocatalyst coatings such as one metal and / or metal oxide plated or coated on another metal or metal oxide. An example of this is an electrocatalyst composed of multiple layers capable of electrochemically reducing carbon dioxide, which can have a synergistic cocatalytic effect and can provide stable long-life performance. It may be a material and a structure. Examples of these are tin particles with an applied surface coating of indium or an alloy of indium and lead or zinc, copper or nickel substrate particles with an applied coating of tin with an upper layer of indium co-electrolytic catalyst. It may be there.

[00130] Further, the metal powder catalyst may contain a metal oxide and a small amount of the noble metal and the noble metal oxide as a coating on the mixture or the electrocatalyst particles. The proportion of these additive components, such as noble metals, may range from 0.001% to 80% or more in the catalyst composition on a weight basis.

Formate CO₂Chemistry of reduction: [00131] CO at the cathode₂The expected chemical reaction of the reduction of is likely to proceed as follows.

As shown in Eq. (1), hydrogen atoms can be adsorbed on the electrode by reducing water.

<chemistry num="1"><img file="JP6599367B2_D0001.tif" /></chemistry>

[00133] As shown in the following formula (2), carbon dioxide can be reduced by hydrogen atoms adsorbed on the cathode surface to form formate, which can be adsorbed on the surface.

<chemistry num="2"><img file="JP6599367B2_D0002.tif" /></chemistry>

As shown in Eq. (3), the formate adsorbed on the surface then reacts with other adsorbed hydrogen atoms to form formic acid, which can be released into solution.

<chemistry num="3"><img file="JP6599367B2_D0003.tif" /></chemistry>

As shown in Eq. (4), the competitive reaction at the cathode may be the reduction of water, where hydrogen gas and hydroxide ions may be formed.

<chemistry num="4"><img file="JP6599367B2_D0004.tif" /></chemistry>

[00136] By operating the electrochemical cell at a higher pressure (higher than atmospheric pressure), it is possible to increase the current efficiency of carbon dioxide to formate and allow the cell to operate at a higher current density. be able to.

Anode reaction: [00137] As shown in equation (5) below, the anodic reaction can be the oxidation of water to oxygen and hydrogen ions.

<chemistry num="5"><img file="JP6599367B2_D0005.tif" /></chemistry>

[00138] The following may be various preferred alternative aspects of the process arranged in different categories. Formate formation from CO: [00139] The thermal intermolecular reaction between alkali metal formate CO and KOH may be as shown in equation (6) below.

<chemistry num="6"><img file="JP6599367B2_D0006.tif" /></chemistry>

[00140] KOH can be consumed in this reaction. Under the correct conditions, both formate and oxalate can be produced, which can reduce the number of process steps. Producing both requires separating these carboxylic acids from each other.

[00141] Further, carbon monoxide can be selectively absorbed in an aqueous solution of an alkali metal carbonate and a bicarbonate to form a formate. This can be shown by the following equations (7) and (8). In the formula, M may be an alkali metal.

<chemistry num="7"><img file="JP6599367B2_D0007.tif" /></chemistry>

<chemistry num="8"><img file="JP6599367B2_D0008.tif" /></chemistry>

[00142] These reactions may not require MOH, such as NaOH or KOH, as a catalyst in the reaction to form M-formate. Formate to Oxalate: [00143] The thermal intermolecular reaction of alkali metal formate with KOH may be as shown in equation (9) below.

<chemistry num="9"><img file="JP6599367B2_D0009.tif" /></chemistry>

[00144] In some cases, sodium or potassium carbonates can be used to convert formate to oxalate, but conversion yields have been shown to be much lower. Under the correct operating conditions and temperature, the yield can be greatly improved.

Anode oxidation reaction: [00145] The anodic reaction is the oxidation of water that produces hydrogen ions and oxygen, which is represented by the following formula (10) when sulfuric acid is used in the anodic solution.

<chemistry num="10"><img file="JP6599367B2_D0010.tif" /></chemistry>

[00146] When hydrobromic acid: HBr is used in the anode solution, the reaction is the oxidation of the bromide to bromine as follows.

<chemistry num="11"><img file="JP6599367B2_D0011.tif" /></chemistry>

[00147] When there is a possibility of using sodium chloride: NaCl in the anodic solution, the anodic reaction in the formate cell or the like in FIG. 5 is the oxidation of chloride ions represented by the following formula (12).

<chemistry num="12"><img file="JP6599367B2_D0012.tif" /></chemistry>

[00148] Sodium ions can be transferred from the anode fluid compartment to the cathode fluid compartment through an ion permeable separator and combined with formate from the reduction of carbon dioxide to form sodium formate, reducing water at the cathode. The hydroxide ion of the by-product formed from can form NaOH.

[00149] If hydrochloric acid: HCl may be used in the anolyte, the reaction may be the oxidation of chloride to chlorine with the co-generation of hydrogen ions, as shown in formula (13) below. There is.

<chemistry num="13"><img file="JP6599367B2_D0013.tif" /></chemistry>

Carbonate-bicarbonate reaction: [00150] Sodium carbonate dissolved in solution: Na₂CO₃Is CO, as shown in equation (14a) below.₂Sodium bicarbonate: Na by reaction with₂HCO₃Can be converted to.

<chemistry num="14a"><img file="JP6599367B2_D0014.tif" /></chemistry>

Similarly, potassium carbonate dissolved in the solution: K₂CO₃CO₂It can be converted to potassium bicarbonate by the reaction with.

<chemistry num="14b"><img file="JP6599367B2_D0015.tif" /></chemistry>

[00151] Sodium hydroxide: NaOH is CO in solution, as shown in formula (15) below.₂Sodium carbonate: Na by reaction with₂CO₃Can be converted to.

<chemistry num="15"><img file="JP6599367B2_D0016.tif" /></chemistry>

Reaction of chlorine with NaOH: [00152] Sodium hydroxide: NaOH can be reacted with chlorine to produce sodium hypochlorite: NaOCl, as shown in formula (16) below.

<chemistry num="16"><img file="JP6599367B2_D0017.tif" /></chemistry>

H⁺Reaction of bicarbonate with ions: [00153] Potassium bicarbonate: KHCO₃Is generated in an electrochemical cell in a cathode cell compartment or the like using a potassium bicarbonate electrolytic solution, as shown in the following formula (17).⁺CO by reacting with ions₂And water can be produced.

<chemistry num="17"><img file="JP6599367B2_D0018.tif" /></chemistry>

Electrolytic cell configuration: [00154] The cell configuration, electrode structure, which can be used in the electrochemical CO and / or cathode, as well as in the electrochemical acidification (EA) electrolytic cell, in the process described above. And various typical combinations of anode / cathode composition are shown.

[00155] The cathode of the electrochemical cell 110 and the electrochemical acidifying electrolytic cell 140 may be a high surface area electrode. The void volume with respect to the cathode may be from about 30% to 98%. Cathode surface area is 2 cm²/cm³~ 500cm²/cm³Or more. The surface area can be further defined as the total area compared to the current distributor / conductor backplate area, with a preferred range of 2 to 1000 times the current distributor / conductor backplate area.

[00156] The cathode of the electrochemical cell 110 may be electroless plated indium or tin on a woven copper mesh, screen, or fiber structure. Indium-copper intermetallic compounds can be formed on copper woven meshes, screens, or fibrous structures. Intermetallic compounds are harder than soft indium metals, allowing for better mechanical properties in addition to catalyst properties suitable for use.

[00157] In the electrochemical reduction of carbon dioxide, the major C is due to metals such as Pb, Sn, Ag, Au, Hg, Tl, In, Bi, and Cd.₁Formic acid (or formate) can be produced in an aqueous solution as a product. In addition to improved catalyst lifetime stability by using alloy combinations of these metals such as Hg-Cu, Sn-Cd, Pb-Bi, Sn-Zn, Cu-Sn, In-Sn, etc. It can provide improved Faradaic performance efficiencies. Some of these individual metal dealloying catalysts themselves, such as Sn and Cu, may inactivate or provide surface changes that indicate a decrease in Faraday conversion activity in producing formate or CO. There is. This metal catalyst surface may then have to be reactivated by reverse current or reverse polarity. CO₂C from₂-In the potential cathode formation of chemicals, or the electrochemical reduction of oxalic acid to products such as glyoxalic acid and glycolic acid, Ti, Nb, Cr, Mo, Ag, Cd, among many others. Metals such as, Hg, Tl, As, and Pd, as well as Cr-Ni-Mo alloy steels, have these higher grade Cs with high Faraday efficiency.₂₊It can give beneficial results in the formation of the product.

[00158] In another aspect, the cathode surface can be regenerated by periodically adding an indium salt or a mixture of indium / tin salts in situ during the operation of the electrochemical cell. The electrochemical cell 110 can be operated at full rate during operation, or can be temporarily operated at a lower current density with or without carbon dioxide added during metal salt infusion.

[00159] In another typical embodiment, C₂₊In the manufacture of cathode materials for the production of chemicals, on the surface of the cathode structure to provide a catalyst surface that may be difficult to form directly during the manufacture of the cathode, or to regenerate the catalyst surface. Addition of a metal salt that can be reduced with, for example, addition of Ag, Au, Mo, Cd, Sn, etc. can also be used.

[00160] In another embodiment, the CO is in a different cell structure with a further compartment having a gas plenum on the cathode structure.₂Direct contact with the gas stream can include a gas diffusion electrode (GDE) that can allow increased current density and Faraday efficiency for formate production. In one aspect of the GDE structure, the GDE electrode is fitted with a central metal screen made from indium-plated tin that forms a gas-permeable but liquid-resistant GDE structure that is compressed and heated. It can contain a mixture of indium particles or indium-coated tin metal particles that can be treated with a PTFE binder to form a paste matrix with a small proportion of non-conductive ceramics. This structure also includes Ultratech, UltraEvershield from International, and other commercial chemicals used to make non-wetting materials such as superhydrophobic materials from NeverWet International. Additions can also be included. Other binders such as graphite and graphene can be used, but this may be undesirable.

[00161] The cathode 412 for the electrochemical acidifying electrolytic cell 140 may include stainless steel and nickel electrodes. The cathode 412 may include a coating on the cathode to reduce hydrogen overvoltage.

[00162] The alkali metal hydroxide range for the electrochemical acidifying electrolytic cell 140 may be from 5% to 50% by weight, more preferably from 10% to 45% by weight. Examples of alkali metal hydroxides may be NaOH, KOH, CsOH and the like.

[00163] CO₂Precious metals and precious metals, as well as Cu, Ag, Au, and oxides thereof, specifically copper oxide, are used as cathode materials for the cathode of the electrochemical cell 110 for producing carbon monoxide from. Can be mentioned. Ag and Ag oxides in mixtures and alloys with other metals can provide better and longer-term electrocatalyst performance. Other d-block metals such as Zn and Ni may be selective for the reduction of CO in aqueous media. CO₂CO regardless of the specificity of CO as a reduction product₂The cathode for the electrochemical cell 110 for an aqueous system to reduce to CO gives a high hydrogen overvoltage to compete H₂The formation can be prevented.

[00164] In other embodiments, a proposed carbon dioxide GDE cathode structure comprising a metal particle electrocatalyst and a multi-coated layer electrocatalyst can also be used to convert carbon dioxide to carbon monoxide: CO. Suitable electrolytic catalysts for this reaction may be silver and silver alloys of mixtures and alloys with other metals such as copper, zinc, gold, and other metals such as transition metals. Other gases such as a useful mixture of CO and hydrogen in ratios suitable for use in the Fischer-Tropsch reaction to produce fuels and organic compounds can co-produce.

[00165] The anion used to generate CO at the cathode may be any species stable at the working potential, such as sulfate, chloride, or bicarbonate. CO to CO₂Reduction of a limited number of competing H₂High pH may be preferred for the formation of saturated CO, but due to the formation of carbonic acid by dissolution, saturated CO₂There may be a practical maximum pH value of about 8.5 for the solution. There may not be an exact lower limit that could be observed. Due to the chemistry of the system, the pH of the cathode solution region of the electrochemical cell 110 may be in the range 3-12. The pH may be a function of the operating conditions of the catalyst and catholyte used so that corrosion in the electrochemical cell 110 can be prevented.

[00166] As electrolytes for the electrochemical cell 110 to form CO and formates, alkali metal bicarbonates, carbonates, sulfates, and phosphates, borates, ammonium, hydroxides. Substances, chlorides, bromides, and other organic and inorganic salts can be mentioned. Electrolyte can also include non-aqueous electrolytes such as propylene carbonate, methanesulfonic acid, methanol, and other ionic conductive liquids, which are either aqueous mixtures or non-aqueous mixtures in cathode solutions. It's okay. By introducing fine bubbles of carbon dioxide into the flow of the cathode liquid, the movement of carbon dioxide to the surface of the cathode can be improved.

[00167] As the electrolytic solution for the anode liquid region of the electrochemical cell 110, in addition to ammonium hydroxide, alkali metal hydroxides (eg, KOH, NaOH, LiOH); inorganic acids such as sulfuric acid, phosphoric acid, etc. Organic acids such as methanesulfonic acid in both non-aqueous and aqueous solutions; and alkali halide salts such as chloride, bromide, and iodide salts such as NaOH, NaCl, NaBr, LiBr, KF, KCl, KBr , KI, and NaI, and their acid halide forms such as HCl and HBr; The alkali halide salt can produce, for example, fluorine, chlorine, bromine, or iodine from the anode solution region as a halide gas or a soluble aqueous product. Methanol or other hydrocarbon non-aqueous liquids can also be used, which form some oxidized organic products from the anodic solution. The choice of anodic solution is determined by the chemical products of the process and the requirements for reducing the total operating cell voltage. For example, when HBr is used as the anode solution to form bromine at the anode, an anode potential much lower than that of chlorine formation is required. Hydrogen iodide: HI can form iodine at an even lower anodic potential than that of bromine.

[00168] The cross-sectional area flow rate of the cathode fluid is 2 to 3,000 gpm / foot²(0.0076 ~ 11.36m³/ m²) Or more. The flow velocity may be in the range of 0.002 to 20 ft / s (0.0006 to 6.1 m / s).

[00169] The cathode solution region of the electrochemical cell 110 can contain at least one type of catalyst. The catalyst may be a homogeneous heterocyclic catalyst that can be used in the cathode solution region to improve the Faraday yield to formate. Examples of the homogeneous heterocyclic catalyst include pyridine, tin 2-picolin, 4-hydroxypyridine, adenine, heterocyclic amine containing sulfur, heterocyclic amine containing oxygen, azoles, benzimidazoles, bipyridine and furan. , Imidazoles, imidazole-related species with at least one 5-membered ring, indols, lutidines, methylimidazoles, oxazoles, phenanthrolines, pterins, pteridines, pyridines, pyridine-related with at least one 6-membered ring Species, pyrroles, quinolines, or thiazoles, and mixtures thereof can be mentioned.

[00170] More dissolved CO by operating the electrochemical cell 110 at a higher operating pressure in the catholyte region.₂Can be made possible to dissolve in an aqueous electrolyte. Normally, electrochemical cells can be operated at pressures up to about 20-30 psig in a multi-cell laminated design, but these can be modified to operate at pressures up to 100 psig. The anode solution of electrochemical cell 110 can also be operated in the same pressure range to minimize the pressure difference on the membrane separating the two electrode regions. In order to operate the electrochemical unit at higher operating pressures up to about 60-100 atmospheres or higher, a special electrochemical design may be required, which is a liquid CO₂Medium and supercritical CO₂It may be in the operating range.

[00171] In other embodiments, part of the catholyte recirculation flow is either back pressure restricted or CO.₂Separately pressurized with the injection using pump 390, the pressurized stream is then injected into the cathode solution region of electrochemical cell 110 to dissolve CO in aqueous solution.₂The amount of can be potentially increased so that the conversion yield can be improved.

[00172] The cathode liquid region and the anode liquid region of the electrochemical cell 110 can be provided with an operating temperature which may be in the range of -10 to 95 ° C, more preferably 5 to 60 ° C. Lower temperatures can be limited by the electrolyte used and their freezing points. In general, the lower the temperature, the more CO in the aqueous phase of the electrolyte.₂Will be more soluble, which will result in higher conversion and current efficiency. However, because the operating voltage of the electrochemical cell can be higher, optimization may be needed to produce the chemical at the lowest operating cost. In addition, the operating temperatures of the anode and cathode fluids can be different, which allows the anode fluid to operate at a higher temperature and the cathode fluid to operate at a lower temperature.

[00173] The electrochemical cell 110 and the electrochemical acidifying electrolytic cell 140 may be a zero-gap once-through electrolytic cell having various high surface area cathode materials for circulating the cathode liquid electrolytic cell. For example, immersion type parallel flow filled bed and trickle bed designs with various high surface area cathode materials can be used. The laminated cell design may be bipolar and / or monopolar.

[00174] The anodes of the electrochemical cell 110 and the electrochemical acidifying electrolytic cell 140 may include one or more anode coatings. For example, for acid anode solutions and for oxidizing water under acidic conditions, it is commonly used in electrocatalyst coatings in the chlorine-alkali industry and other electrochemical processes in which they can be stable as anodes. Inclusion of ruthenium and iridium oxides on valve metal conductive substrates such as titanium, tantalum, or anode, and precious metals and noble metal oxides such as platinum and gold and their combinations as metals and oxides. Can be done. For other anode solutions such as alkaline or hydroxide electrolytes, the electrolytic catalyst coating can be stable as an anode under carbon, graphite, cobalt oxide, nickel, stainless steel, and these alkaline conditions. These alloys and combinations can be included.

[00175] Membranes 330, 406a, 406b may be cation ion exchange type membranes such as those having high removal efficiency for anions. For example, DuPont Manufactured by Nafion® brand non-reinforced N117 and N120 series, more preferably PTFE fiber reinforced N324 and N424 types, and supplier trade names such as Flemion® by Japanese companies. Perfluorinated sulfonic acid-based ion exchange membranes such as similar related membranes. Using other multilayer perfluorinated ion exchange membranes with a two-layer structure of a sulfonic acid-based membrane layer bonded to a carboxylic acid-based membrane layer used in the chlorine-alkali industry, the pH is about 2 or more. It can be operated efficiently with higher pH anode and cathode solutions. These membranes may have higher anion removal efficiency. These may be sold by DuPont under the Nafion® trademark as the N900 series, such as the N90209, N966, N982, and the 2000 series, such as the N2010, N2020, and N2030. All types and subtypes are included. If anion removal may not be important, especially by Sybron in their trade name lonac®, AGC Using hydrocarbon-based membranes that can be made from a variety of cation ion exchange materials, such as those sold by Engineering (Asahi Glass) under their Selemion® and sold by Tokuyama Soda. You can also.

<p> Experiments on the thermal conversion of alkali metal formates to oxalates: [00176] Experiments were conducted to determine some process conditions for the thermal conversion of alkali metal formates. The temperature, calcination time, and addition of various catalysts that could improve the yield on oxalic acid were evaluated. Carbonates were determined by standard methods by titration with HCl and pH indicators.</p><p> Example 1: [00177] Table 1 shows the results of a series of experiments performed in a heating furnace using a nitrogen atmosphere. This experiment was performed to evaluate the conditions and yields of alkali metal formate in thermal conversion. The use of various catalysts was evaluated by varying the temperature and calcination time. These samples were prepared using reagent-grade potassium formate crystals and adding reagent-grade potassium hydroxide pellets. The chemical reagents were mixed together and placed in a 100 mL nickel crucible. The crucible was calcinated at the time and temperature given in Table 1. The yield (%) of potassium formate to potassium oxalate using a potassium hydroxide catalyst was in the range of 73.71% to 78.53% between 0.5 and 1.0 hours at 420 ° C. Oxalate content was analyzed by both permanganate titration and ion chromatography. At 440 ° C, the conversion yield to oxalate was about 77%.</p><p><tables num="1"><img file="JP6599367B2_D0019.tif" /></tables></p><p> Example 2: [00178] Table 2 shows the results of the same procedure as in Example 1 except that potassium bicarbonate was added to potassium formate as a co-product or potential catalyst. The calcination temperature was 420 ° C. for 30 minutes in a nitrogen atmosphere in a heating oven.</p><p><tables num="2"><img file="JP6599367B2_D0020.tif" /></tables></p><p> Example 3: [00179] Table 3 shows the results of the same procedure as in Example 1 in which KOH was added to potassium formate as a catalyst. The calcination temperature was 440 ° C. for 30 minutes in a nitrogen atmosphere in a heating oven. Table 4 shows the results without the KOH catalyst.</p><p><tables num="3"><img file="JP6599367B2_D0021.tif" /></tables></p><p><tables num="4"><img file="JP6599367B2_D0022.tif" /></tables></p><p> Example 4: [00180] Table 5 shows the results of the same procedure as in Example 1 in which KOH was added to potassium formate as a catalyst. The calcination temperature was 480 ° C for 30 minutes in a nitrogen atmosphere in a heating oven. Table 6 shows the results without the KOH catalyst.</p><p><tables num="5"><img file="JP6599367B2_D0023.tif" /></tables></p><p><tables num="6"><img file="JP6599367B2_D0024.tif" /></tables></p><p> Example 5: [00181] Table 7 shows the results of the same procedure as in Example 1 in which magnesium oxide powder was added to potassium formate as a catalyst. The calcination temperature was 420 ° C. in a nitrogen atmosphere in a heating oven.</p><p><tables num="7"><img file="JP6599367B2_D0025.tif" /></tables></p><p> Example 6: [00182] Table 8 shows sodium borohydride (NaBH).₄) The result of the same procedure as in Example 1 in which powder was added to potassium formate as a catalyst is shown. The calcination temperature was 440 ° C in a nitrogen atmosphere in a heating oven. Table 9 shows NaBH as a cocatalyst at the same temperature.₄And the results using KOH are shown.</p><p><tables num="8"><img file="JP6599367B2_D0026.tif" /></tables></p><p><tables num="9"><img file="JP6599367B2_D0027.tif" /></tables></p><p> Example 7: [00183] Table 10 shows the results of the same procedure as in Example 1, except that sodium hydride (NaH) powder was added to sodium formate as a catalyst. The calcination temperature was 440 ° C in a nitrogen atmosphere in a heating oven.</p><p> [00184] Table 11 shows the results of using NaH as a catalyst in potassium formate at various times and temperatures.</p><p><tables num="10"><img file="JP6599367B2_D0028.tif" /></tables></p><p><tables num="11"><img file="JP6599367B2_D0029.tif" /></tables></p><p> Conversion of Oxalic Acid to Glyoxylic Acid: [00185] With reference to FIG. 18, chemical derivatives that may start from oxalic acid as the initial chemical feedstock according to one aspect of the invention are shown. Glycine (aminoacetic acid) is an industrial chemical substance with many uses. It has a wide range of uses as an additive for human and animal foods and as an intermediate in the synthesis of numerous chemicals. At this time, glycine is commercially produced from the reaction of chloroacetic acid with ammonia. Since carbon dioxide is one of the cheapest potential chemical feedstocks, the economic pathways for producing chemicals such as glycine from carbon dioxide have advantages over current conventional routes. Can be given. Another important chemical is ethylene glycol, which can be made using oxalic acid as a raw material. Ethylene glycol is used in billions of pounds per year in the production of bottles made from polyethylene terephthalate used in antifreeze and in bottled consumer beverages.</p><p> [00186] With reference to FIG. 19, a schematic diagram showing a block diagram of the system for converting carbon dioxide to glycine is shown. The system can include Unit A, which contains an electrochemical cell for converting carbon dioxide feed material to oxalate, which is then sent onto Unit B to convert oxalate to oxalic acid. Then the oxalic acid is sent to unit C, where the oxalic acid is electrochemically reduced to glyoxylic acid, the glyoxylic acid is sent to the reducing amination unit, and ammonia and hydrogen are added as a product. Convert to glycine. Solvents and intermediates that pass between the various units in FIG. 19 and the purification step are not shown.</p><p> [00187] With reference to FIG. 20, a schematic diagram showing an electrochemical cell for reducing oxalic acid to produce a glyoxylic acid product is shown. The electrochemical cell includes an anode liquid compartment containing an anode, a cathode liquid compartment containing a cathode, and a membrane or separator separating the two compartments. An oxalic acid supply stream is supplied into the cathode solution compartment of the electrochemical cell and reduced to glyoxylic acid at the cathode. The glyoxylic acid product is separated from the recirculating cathode fluid stream in the cathode fluid dissociator, where the gaseous by-product gas from the reduction reaction is also separated. The catholyte solution is recirculated back to the catholyte compartment using a catholyte recirculation pump. Cathodic solutions can contain a variety of selected acids, which may be inorganic or organic acids in aqueous or non-aqueous based solutions.</p><p> [00188] The cathode liquid compartment is a cathode current collector or current distributor, and a high surface area cathode formed from a metal or alloy, and an electrolytic catalyst coating on a metal suitable for efficiently reducing glyoxylic acid to glycine. Includes a cathode structure that includes. These include, but are not limited to, metals such as Cd, Pb, Hg, Bi, Sb, PbSb, as well as alloys and oxides thereof.</p><p> [00189] The anode fluid compartment comprises the anode and optionally a high surface area structure. The anodic reaction can generate oxygen, for example when mineral acids such as sulfuric acid, phosphoric acid, and nitric acid are used, or organic such as methanesulfonic acid, which is stable to the oxygen-producing anodic reaction. Acids can be used. Suitable anode materials for these acid anode solutions are coatings of noble metal oxides such as ruthenium and iridium oxides, and as metals and oxides on valve metal substrates such as titanium, tantalum, or niobium. Platinum and gold and combinations thereof.</p><p> [00190] The anode material for this electrochemical cell comprises carbon materials such as carbon and graphite, which may be in the form of felt, needle felt, or woven fabric, the electrochemical shown in FIGS. 1-3. Similar to those used in the electrochemical cells that produce graphite disclosed in this application, such as cells. These carbon-based materials can provide catalysts that are impregnated in or on the surface of high surface carbon structures, which are preferably chemically resistant to the bromination chemical reaction of the anode. Includes platinum group metals and oxides, mixtures and alloys thereof, such as gold, platinum, ruthenium dioxide, iridium oxide, which can be and can help promote or catalyze the oxidation of bromide to bromine. Other suitable anode materials may be various noble metal family metals and oxides, mixtures thereof, and valve metals such as titanium, niobium, and tantalum with an electrolytic catalyst surface coating of these alloys. These anodic materials are used when using solutions containing acid halides such as HCl and HBr when producing halogens in the anodic solution compartment, which results in chlorine or bromine from the anodic compartment as products, respectively. Generate.</p><p> [00191] The separator and membrane materials used for the glyoxylic acid reduction cell are also of the same type as those used in the oxalate-producing cells disclosed in this application. [00192] With reference to FIG. 21, a schematic diagram showing a reductive amination batch reactor system for converting glyoxylic acid to glycine is shown, which is the feed inlet, recirculation flow, and final glycine production. Includes a batch reactor system that provides purification of the material. Separation of glycine from the solvent can be carried out by various processes such as distillation or extraction distillation.</p><p> [00193] In one embodiment, the reductive amination of oxalic acid to glycine is preferably carried out in the reactor. The proposed chemical reactions for reductive amination are as follows.</p><p><chemistry num="18"><img file="JP6599367B2_D0030.tif" /></chemistry></p><p> The glyoxylic acid product produced using the electrochemical cell shown in FIG. 20 is fed to a reactor containing a water-soluble organic solvent, water, and a hydrogenation catalyst of choice. Next, ammonia and hydrogen are metered into the reactor at a specific molar ratio, and further hydrogen is added while hydrogen is being consumed during the reaction to allow the reaction to proceed while maintaining a constant hydrogen pressure. ..</p><p> [00195] Ammonia can be used either as an aqueous solution of ammonia or as liquid ammonia. Ammonia is NH₃: Glyoxylic acid can be used in a molar ratio range of 1.2 to 20, more preferably 1.5 to 10, more preferably 2 to 5, in excess of the required theoretical amount (Reaction 18).</p><p> [00196] A number of water-soluble organic solvents can be used in the reactor to retain the reactants and products in the reactor in the solution. These solvents must be preferably non-reactive with glyoxylic acid and glycine products and can be easily recovered from the glycine products in subsequent separation and purification steps.</p><p> Suitable solvents include alcohols such as methanol, ethanol, isopropanol, and tert-butanol, as well as other water-miscible solvents such as 1,4-dioxane, tetrahydrofuran, piperidin, and mixtures thereof. Be done. Methanol and ethanol may be the preferred solvents.</p><p> [00198] The ratio of the water-soluble organic solvent to water is calculated to keep the reactants and reaction products in solution and promote the conversion of glyoxylic acid to glycine. When methanol is used as the organic solvent, a solvent mixture containing about 60% methanol and 40% water can be used. The amount of methanol may range from about 20 to about 70% by weight of methanol in the methanol / water solvent mixture.</p><p> [00199] The reductive amination reactor also uses a suitable hydrogenation catalyst. Suitable catalysts are platinum group metals and some transition metals such as ruthenium, rhodium, nickel, palladium, platinum, osmium, and alloys and mixtures thereof. Rhodium has been found to be an effective catalyst in the production of high yield glycine. The catalyst may be in the form of particles of elemental material deposited on a carrier substrate such as carbon, silica, and alumina. The catalyst may be in the form of a slurry suspension that can be used in a batch reactor or in the form of a fixed catalyst bed used in a continuous reactor (preferably).</p><p> [00200] The amination reactor may be of batch or continuous type, wherein it is equipped with means for vigorous stirring and shaking and for introducing hydrogen gas under the desired pressure in the reactor. Place the reactants in a pressure vessel accompanied by this. The reaction pressure may be in the range of 20 psig to 3,000 psig depending on the catalyst used and the temperature conditions.</p><p> [00201] The reductive amination reaction temperature is in the range of 0 ° C to 100 ° C, preferably 10 ° C to 60 ° C, depending on the reaction temperature used in the reaction, the choice of catalyst, or the solvent. It can preferably be in the range of about 15 ° C to 40 ° C. The preferred conversion yield is 80% or higher, more preferably 90% or higher.</p><p> Experimental Results: [00202] The following is a summary of the results when determining the products of the electrochemical reduction of oxalic acid using various cathode materials.</p><p> [00203] In this test group, the electrochemical reduction of oxalic acid in batch reactors with various cathode materials was investigated. The best Faraday yields (FY) for producing glycolic acid and glyoxylic acid were 60% and 75% for direct reduction of oxalic acid, respectively. A 95% FY was also achieved for the reduction of glyoxylic acid to glycolic acid. Traces of monoethylene glycol (MEG) were observed using the Cd cathode. Factors most influencing the Faraday yield of glycolic acid and glyoxylic acid include the cathode material, potential, and temperature, while the effects of the electrolyte were found to be negligible. No factor affecting the yield of ethylene glycol was found, as the system for producing significant amounts of MEG is not yet known.</p><p> Cathode manufacturing: [00204] Cathode material was cleaned by standard procedures to obtain a renewable surface. In a typical experiment, about 2 cm from bulk metal²The metal pieces were cut out, polished with alumina powder (0.3 μm), rinsed with deionized water, and degreased with acetone. The electrodes thus cleaned were sonicated in deionized water for 2 minutes. Prior to use, the electrodes were dried by pressing between clean Kimwipe.</p><p> Bulk electrolysis: [00205] Arbin MSTAT 167563 Electrolysis was performed at a constant potential using a constant potential electrolyzer (Arbin Instruments). Unless otherwise indicated, all electrolysis was performed in a three-chamber glass cell with separate cathode and anode chambers. For electrolysis using a mercury cathode, a two-chamber electrochemical device with a cathode chamber separated by a glass frit was used. Insulated copper wire was used to form a connection between the liquid mercury on the cathode and the constant potential electrolyzer. Various forms of carbon were tested for anode compatibility.</p><p> Product Analysis: [00206] Quantification of glycolic acid and glyoxylic acid was performed by ion chromatography (IC). Other analytical objects were quantified by NMR. Analytical samples for NMR are 800 μL sample, 100 μL D₂O and 100 μL of H₂Prepared as 1000 ppm acetone in O. These were run for 1 hour using solvent suppression. Quantification was performed based on the relative peak area using the response coefficients calculated from the prepared standard mixture. In the table below, Ox refers to oxalic acid.</p><p><tables num="12"><img file="JP6599367B2_D0031.tif" /></tables></p><p><tables num="13"><img file="JP6599367B2_D0032.tif" /></tables></p><p><tables num="14"><img file="JP6599367B2_D0033.tif" /></tables></p><p><tables num="15"><img file="JP6599367B2_D0034.tif" /></tables></p><p><tables num="16"><img file="JP6599367B2_D0035.tif" /></tables></p><p> [00207] Another anolyte solution can be used to produce bromine-like chemical products in the anode region of electrochemical cell 110, which is based on the chemical characteristics of ethanol, ethylene, and bromine. It can be used to bromide organic compounds as an intermediate in the production of chemicals. Sodium sulfide or SO₂It is also intended to oxidize the sulfur compounds in the anode solution region, such as, or to directly or indirectly oxidize the organic compounds, and to partially oxidize the organic compounds, such as methanol, to formaldehyde.</p><p> [00208] Various alkali metal hydroxides can be used in the electrochemical cells 110 and / or the thermal reactors 120, 130. For example, hydroxides of lithium, sodium, potassium, and rubidium, as well as cesium can be used. Furthermore, alkaline earth metal hydroxides can also be used.</p><p> [00209] The thermal reactors 120 and 130 can carry out a thermal intermolecular condensation reaction using an alkali metal hydroxide. Such a condensation reaction can include a chemical reaction involving the loss of a small molecule by combining two molecules or groups (functional groups) to form a single molecule. This condensation can be called intermolecular if two separate molecules can be reacted. Since the reaction occurs at elevated temperatures, this reaction can be characterized as a "thermal intermolecular condensation step". This reaction can be characterized as a "thermal intermolecular dehydration step" if water can be lost. These reactions can be carried out in an aqueous phase such as a reaction between CO and an alkali metal hydroxide or a melt of an alkali metal carboxylic acid and an alkali metal hydroxide in a thermal reaction.</p><p> [00210] Thermal reactors 120, 130 can be operated at about 40-500 ° C, more preferably about 50-450 ° C. The operating temperature can be determined by the decomposition temperature of the carboxylic acid and the optimum temperature for obtaining the highest yield of the carboxylic acid product. The residence time of the reaction at the optimum reaction temperature may range from 5 seconds to several hours, and the device selected to carry out the reaction provides the heating and cooling rates required to obtain the optimum conversion yield. Can be designed as This can include the use of cold rotating metals that can quickly cool the hot thermal products after the thermal reaction time may have completed.</p><p> [00211] Thermal reactors 120, 130 can be operated in an air or oxygen enriched atmosphere and in an atmosphere of an inert gas such as nitrogen, argon, and helium. Carbon dioxide and hydrogen atmospheres, as well as partial CO atmospheres, can also be used to obtain the highest yields in the reaction. Thermal reactors 120, 130 may be operated under full or partial vacuum.</p><p> [00212] The use of CO from other sources, such as from the production of syngas from methane or natural gas reforming, can be used. CO can also come from other sources, such as process waste streams, if it can be separated from carbon dioxide.</p><p> [00213] The concentration range of the alkali metal hydroxide may be 2% to 99%, more preferably 5 to 98% on a weight basis. Alkali hydroxides can be operated in a molar excess of alkali metal carboxylic acids to be heat treated in the initial reaction mixture, or in a continuous process in which they can be mixed together. The predicted molar ratio of alkali metal carboxylic acid to alkali metal hydroxide may be in the range of 0.005 to 100, more preferably 0.01 to 50. It may be preferable to use the smallest possible amount of alkali metal hydroxide to carry out the reaction so as to reduce the consumption of hydroxide in the process.</p><p> [00214] Examples of process operating devices that can be used for the thermal reactors 120, 130 include various commercially available types. The device that can be used for the reaction of the alkali metal hydroxide with CO may be a batch operation device that can inject a gas into the solution mixture of the alkali hydroxide. This can also be done in a continuous manner, in which case there can be a feed inlet into the new alkali metal hydroxide continuous stirred tank reactor (CSTR) and the supply of CO into the solution. This is done through a gas stirrer into the solution. Alternatively, a countercurrent filling column can be used, in which case CO can be injected into the column by countercurrent flow into the stream of alkali metal hydroxides.</p><p> [00215] For the operation of alkali metal oxalates, thermal reactors 120, 130, devices such as rotary kilns, and processes with alkali metal formates and alkali hydroxides as solid or hot melt mixtures. A single-pass plug flow reactor that can be used when heat treatment is required can be included. Preferably, the device can be operated continuously with the dwell time required to complete the reaction at the temperature of choice, followed by a cooling section.</p><p> [00216] The thermal intermolecular condensation process can also be carried out to produce a carboxylic acid with a higher carbon content and convert the carboxylic acid to esters, amides, acid chlorides, and alcohols. In addition, the carboxylic acid product can be converted to the corresponding halide compound with bromine, chlorine, and iodine.</p><p> [00217] Examples of the catalyst for thermal conversion of alkali metal formate include various bases such as alkali metal hydroxides and other compounds which are bases. Furthermore, alkali metals and other hydrides can be used as they also act as bases. Any other suitable catalyst that may be compatible with formate in calcination and can give high conversion yields is suitable for the process.</p><p> [00218] It is intended that the structure and operation of the electrochemical cells described herein, such as the electrochemical cell 110, can be adjusted to give the desired results. [00219] For example, an electrochemical cell can be operated at a higher pressure, such as a pressure higher than atmospheric pressure, which increases current efficiency and allows the electrochemical cell to be operated at a higher current density. Can be made possible.</p><p> [00220] Further, the cathode and anode of the electrochemical cell can include a high surface area electrode structure having a void capacity which may range from 30% to 98%. The percent void volume of the electrode can refer to the percentage of empty space that the electrode does not occupy in the total volume space of the electrode. The advantage of using electrodes with high void capacity is that the structure has a lower pressure drop with respect to the liquid flow through the structure. The specific surface area of the electrode group structure is 2 cm.²/cm³~ 500cm²/cm³Or more. The specific surface area of the electrode is the ratio of the surface area of the electrode base structure divided by the total physical volume of the entire electrode. This surface area can also be defined as the total area of the electrode substrate compared to the projected geometric area of the current distributor / conductor back plate, with a preferred range of 2 to 1000 times or more. The actual total active surface area of the electrode structure is a function of the properties of the electrode catalyst deposited on the physical electrode structure, which is 2 to 1000 times larger in surface area than the physical electrode base structure. It's okay.</p><p> [00221] The cathode can be selected from a number of high surface materials, including copper, stainless steel, transition metals and their alloys, carbon, and silicon, which may be conductive metals or semiconductors. It can be further coated with a layer. The base structure of the cathode may be in the form of a fiber, metal foam, reticulated material, or sintered powder material formed from other conductive materials, including metals, carbon, or polymers. The material may be a very thin plastic screen included in contact with the cathode side of the membrane so that the membrane does not come into direct contact with the high surface area cathode structure. The high surface area cathode structure can be mechanically pressed against a cathode current distributor back plate, which may be made of a material having the same surface composition as the high surface area cathode.</p><p> [00222] Further, the cathodes are Al, Au, Ag, Bi, C, Cd, Co, Cr, Cu, Cu alloys (eg brass and bronze), Ga, Hg, In, Mo, Nb, Ni, NiCo.₂O₄, Ni alloys (eg Ni625, NiHX), Ni-Fe alloys, Pb, Pd alloys (eg PdAg), Pt, Pt alloys (eg PtRh), Rh, Sn, Sn alloys (eg SnAg, SnPb, SnSb), Ti, V, W, Zn, Stainless Steel (SS) (eg SS2205, SS304, SS316, SS321), Austenite Steel, Ferrite Steel, Two Phase Steel, Martensite Steel, Nichrome (eg NiCr 60:16 (with Fe)) ), Elgiloy (eg Co-Ni-Cr), reduced dope n-Si, reduced dope n-Si: As, reduced dope n-Si: B, reduced dope n-Si, reduced dope n-Si: As, and withdrawal It may be a suitable conductive electrode such as dope n-Si: B. Other conductive electrodes can be mounted to meet criteria for a particular application. For photoelectrochemical reduction, the cathode 122 is p-GaAs, p-GaP, p-InN, p-InP, p-CdTe, p-GaInP.₂, And p-type semiconductor electrodes such as p-Si, or n-GaAs, n-GaP, n-InN, n-InP, n-CdTe, n-GaInP₂, And n-type semiconductors such as n-Si. CoS, MoS₂, TiB, WS₂, SnS, Ag₂S, CoP₂, Fe₃P, Mn₃P₂, MoP, Ni₂Si, MoSi₂, WSi₂, CoSi₂, Ti₄O₇, SnO₂Other semiconductor electrodes such as, GaAs, GaSb, Ge, and CdSe (but not limited to these) can be mounted to meet the criteria of a particular application.</p><p> [00223] The cathode solution may have a pH range of 1-12, preferably 4-10. The operating pH selected may be a function of the catalyst used in the operation of the electrochemical cell. Preferably, the cathode solution and catalyst can be selected to prevent corrosion in the electrochemical cell. The cathode solution can contain a homogeneous catalyst. Homogeneous catalysts are defined as aromatic heterocyclic amines and may include, but are not limited to, unsubstituted and substituted pyridines and imidazoles. Examples of the substituted pyridines and imidazoles include, but are not limited to, mono- and di-substituted pyridines and imidazoles. For example, a suitable catalyst is a straight chain or branched chain lower alkyl (eg C).₁~ C₁₀) Mono and di-substituted compounds such as 2-methylpyridine, 4-tert-butylpyridine, 2,6-dimethylpyridine (2,6-lutidine); bipyridines such as 4,4'-bipyridine; amino-substituted pyridines such as 4-Dimethylaminopyridine; and hydroxyl-substituted pyridines (eg 4-hydroxypyridine), as well as substituted or unsubstituted quinolines or isoquinolins. The catalyst may also preferably include substituted or unsubstituted dinitrogen heterocyclic amines such as pyrazine, pyridazine, and pyrimidine. Other catalysts generally include azoles, imidazoles, indoles, oxazoles, thiazoles, substituents and complex polycyclic amines such as adenine, pterin, pteridine, benzimidazole, phenanthroline and the like.</p><p> [00224] The cathode solution can contain an electrolytic solution. Examples of the cathode liquid electrolytic solution include alkali metal bicarbonate, carbonate, sulfate, phosphate, borate, and hydroxide. Instead of water, non-aqueous electrolytes such as propylene carbonate, methanesulfonic acid, and methanol, and other ionic conductive liquids can be used, and salt-added electrolytes such as alkali metal salts can be used. The electrolyte is Na₂SO₄, KCl, NaNO₃, NaCl, NaF, NaClO₄, KClO₄, K₂SiO₃, CaCl₂, Guanidinium cation, H cation, alkali metal cation, ammonium cation, alkylammonium cation, tetraalkylammonium cation, halide anion, alkylamine, borate, carbonate, guanidinium derivative, nitrite, nitrate, phosphate , Polyphosphates, perchlorates, silicates, sulfates, and hydroxides can be included.</p><p> [00225] The cathode solution can further contain an aqueous or non-aqueous solvent. The aqueous solvent can contain more than 5% water. The non-aqueous solvent can contain about 5% water. The solvent can include one or more of water, a protic and aprotic solvent, or an aprotic polar solvent. Typical solvents include methanol, ethanol, acetonitrile, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, dimethyl sulfoxide, dimethylformamide, acetonitrile, acetone, tetrahydrofuran, N, N-dimethylacetamide, dimethoxyethane, diethylene glycol dimethyl ester. , Butyronitrile, 1,2-difluorobenzene, γ-butyrolactone, N-methyl-2-pyrrolidone, sulfoxide, 1,4-dioxane, nitrobenzene, nitromethane, anhydrous acetic acid, ionic liquids, and mixtures thereof.</p><p> [00226] In one aspect, the flow rate of the cathode / anode fluid is 2 to 3,000 gpm / foot.²(0.0076 ~ 11.36m³/ m²) Or more such as cathode / anode fluid cross-sectional area flow rate range. The flow velocity range may be 0.002 to 20 ft / s (0.0006 to 6.1 m / s). By operating the cathode solution of the electrochemical cell at a higher operating pressure, more dissolved carbon dioxide can be dissolved in the aqueous solution. Normally, the electrochemical cell can be operated at a pressure of up to about 20-30 psig in a multi-cell laminated design, but with modifications the electrochemical cell can be operated at a pressure of up to 100 psig. The electrochemical cell can operate the anode and cathode fluids in the same pressure range to minimize the pressure difference on the separator 120 or membrane that separates the two regions. A special electrochemical design can be used to operate the electrochemical unit at higher operating pressures up to about 60-100 atmospheres or higher, which is a liquid CO₂Medium and supercritical CO₂It is a driving range.</p><p> [00227] In other embodiments, part of the catholyte recirculation flow is either back pressure restricted or CO.₂Along with the injection, another pressurization is performed using a pump, and the pressurized flow is then injected into the cathode solution region of the electrochemical cell to dissolve the dissolved CO in the aqueous solution.₂The amount of can be increased so that the conversion yield can be improved. Further, by various means, it is possible to generate fine bubbles of carbon dioxide in the recirculating flow of the cathode liquid to maximize the solubility of carbon dioxide in the solution.</p><p> [00228] The cathode fluid can be operated in the temperature range of -10 to 95 ° C, more preferably 5 to 60 ° C. Lower temperatures are limited by the cathode fluid used and their freezing points. In general, the lower the temperature, the more CO in the aqueous phase of the cathode solution.₂The solubility of the is higher, which helps to obtain higher conversion and current efficiency. The disadvantage is that the operating voltage of the electrochemical cell can be higher, so optimization may be performed to produce the chemical at the lowest operating cost. In addition, since the cathode fluid may need to be cooled, an external heat exchanger is used to allow some or all of the cathode fluid to flow through the heat exchanger, and cooling water is used to remove the heat. The temperature of the cathode liquid can be controlled.</p><p> [00229] The operating temperature of the anode fluid may be in the same range as for the cathode fluid and may be in the range 0 ° C to 95 ° C. In addition, since the anode fluid may need to be cooled, an external heat exchanger is used to allow some or all of the anode fluid to flow through the heat exchanger and cooling water to remove the heat. The temperature of the anode liquid can be controlled.</p><p> [00230] The electrochemical cell can include various types of designs. These designs include a zero-gap design with a limited amount or zero gap between the electrode and the membrane, a flow or permeation design with recirculation of the cathode solution electrolyte using a variety of high surface area cathode materials. it can. Electrochemical cells can include immersion type parallel and countercurrent filled beds and trickle bed designs with a variety of high surface area cathode materials. It is also possible to use a bipolar laminated cell design and a high pressure cell design for the electrochemical cell.</p><p> [00231] The anode electrode may be the same as or different from the cathode electrode. Preferred electrocatalyst coatings for sulfur dioxide and hydrogen sulfide anodic oxidation chemical reactions under acidic conditions include noble metal oxides such as ruthenium and iridium oxides, as well as valve metal substrates such as titanium, tantalum, zirconium, or niobium. Platinum and gold as the above metals and oxides and combinations thereof can be included. Carbon and graphite may also be suitable for use as anodes in addition to boron-doped diamond films on metals or other conductive substrates. Carbon, the transition Metals, transition metal oxides, carbon steels, stainless steels, and alloys and combinations thereof that are stable as anodes can be mentioned. The anode can include an electrocatalyst coating applied to the surface of the base anode structure. The anolyte may be the same as or different from the catholyte. The anolyte electrolyte may be the same as or different from the catholyte electrolyte. The anolyte can contain a solvent. The anodic solution solvent may be the same as or different from the cathode solution solvent. For example, SO as a sulfur-based reactant₂Preferred electrolytic catalyst coatings for acid anode solutions include noble metal oxides such as ruthenium and iridium oxides, as well as metals and oxides on valve metal substrates such as titanium, tantalum, zirconium, or niobium. Platinum and gold and combinations thereof can be included. For other anode solutions such as alkaline or hydroxide electrolytes, the anode can include carbon, cobalt oxides, stainless steel, transition metals, and alloys, oxides, and combinations thereof. High surface area anode structures can be used that help facilitate the reaction at the anode. The high surface area anode base material may be in a reticulated form composed of fibers, sintered powder, sintered screens, etc., and is sintered, welded, or machined to a current distributor back plate commonly used in bipolar cell assemblies. Can be connected. In addition, the high surface area reticulated anode structure also has SO in the anode fluid.₂Catalysts are further applied on or near the electrocatalystally active surface of the anode surface structure to enhance and facilitate reactions that may occur in bulk solutions away from the anode surface, such as the introduction of It can also include the area in which it exists. The anode structure can be stepped to allow for easier separation of gas from the anode structure by suitable changes in the vertical or horizontal direction. In this staging, Co, Ni, Mn, Zn, which can be deposited on the inorganic carrier in the space of the cathode compartment, or externally such as in the extractor or another reactor of the second product, It contains transition metal-based oxides such as those based on transition metals such as Cu and Fe, as well as catalysts such as platinum, gold, silver, and palladium based noble metals and their oxides. There may be a distribution of particles of material mixed in a good anode structure.</p><p> [00232] The separator of the electrochemical cell, which is also called a membrane, can be arranged between the anode region and the cathode region of the electrochemical cell. Examples of the separator include a cation ion exchange type membrane. A cation ion exchange membrane having a high removal efficiency for anions may be preferable. Examples of such cation exchange membranes are DuPont Nafion® brand non-reinforced N117 and N120 series, more preferably PTFE fiber reinforced N324 and N424 types, and AGC Engineering (Asahi). To name a perfluorinated sulfonic acid-based ion exchange membrane such as a similar related membrane manufactured by a Japanese company such as Glass) under the supplier trade name under their trade name of Flemion®. Can be done. Other multilayer perfluorinated ion exchange membranes used in the chloralkali industry may have a two-layer structure of a sulfonic acid-based membrane layer attached to a carboxylic acid-based membrane layer, which is about. It is operated efficiently using an anode solution and a cathode solution having a pH of two or more. These membranes may have higher anion removal efficiency. They are sold by DuPont under the N900 series, such as N90209, N966, N982, and the 2000 series, such as N2010, N2020, and N2030, as well as all of these types and subtypes under the Nafion® trademark. ing. If lower anion removal efficiency is not important, among those sold by Sybron, under their trade name lonac®, AGC Engineering (Asahi) Hydrocarbon-based membranes made from a variety of cation-ion exchange materials, such as those sold by Glass) under their Selemion® and by Tokuyama Soda, can also be used. Known by the generic name of NASICON (for sodium superion conductors), which is chemically stable to a variety of chemicals over a wide pH range and selectively transports sodium ions, its composition is Na._{1 + x}Zr₂Si_xP_3-xO₁₂Ceramic-based films that are based on titanium oxides, zirconium oxides, and yttrium oxides, as well as other ceramic-based conductive films based on β-aluminum oxides can also be used. Another membrane that can be used is one that has a different structural skeleton, such as polyphosphazene and sulfonated polyphosphazene membranes, in addition to crown ether based membranes. Preferably, the membrane or separator is chemically resistant to the anodic and cathodic solutions.</p><p> [00233] The rate of formation of reactants formed in the anode and cathode fluid compartments may be proportional to the current applied to the electrochemical cell. The extractor and its selected separation method, such as the operation of fractional distillation or packing tower scrubbing, the actual product produced, and the selectivity of the desired reaction determine the optimum molar ratio of reactants to the reactants produced. ..</p><p> [00234] Electrochemical cell is 3kA / m²(300mA / cm²) Higher or 0.5 ~ 5kA / m²It can be easily operated with a current density within a suitable range of, or higher if necessary. The anode preferably fills the gap between the cathode back plate and the membrane, thus giving a zero-gap anode structure, 50 cm.²/cm³It has a high surface area structure having a specific surface area of one or more. A metal and / or metal oxide catalyst can be added to the anode to reduce the anode potential and / or increase the anode current density. Stainless steel or nickel can also be used as the anode material for the oxidation of sodium sulfide under alkaline conditions.</p><p> It is understood that the specific order or sequence of steps in the disclosed method is an example of a representative approach. It is understood that the specific order or sequence of steps in the method can be rearranged based on design preferences, while maintaining within the scope of the disclosed subject matter. The attached method claims represent some component of the various steps in the sample order and are not necessarily intended to be limited to the specific order or order shown.</p><p> [00236] The present invention and many of its advantages are believed to be understood by the description above, without departing from the disclosed subject matter or at the expense of all of its significant advantages. It will be clear that various changes can be made in form, composition, and arrangement of components. The forms described are merely exemplary and it is the intent of the claims to include and embrace such changes.<u style="single">[Aspects of the Invention]</u><u style="single">[1]</u><u style="single"> Receiving a supply stream of hydrogen gas in the anode fluid region of an electrochemical cell containing an anode containing a gas diffusion electrode;</u><u style="single"> Accepting the anodic fluid supply stream in the anodic fluid region of the electrochemical cell;</u><u style="single"> Receiving a cathode fluid supply stream containing carbon dioxide and alkali metal bicarbonate in the cathode fluid region of the electrochemical cell containing the cathode;</u><u style="single"> Applying sufficient potential between the anode and cathode of the electrochemical cell to reduce carbon dioxide to the reduction product.</u><u style="single">A method of reducing carbon dioxide, including.</u><u style="single">[2]</u><u style="single"> Receiving a supply stream of carbon dioxide gas in the cathode fluid region of an electrochemical cell containing the cathode</u><u style="single">The method of [1], which further includes.</u><u style="single">[3]</u><u style="single"> The method of [2], in which the cathode includes a gas diffusion electrode.</u><u style="single">[4]</u><u style="single"> The method of [1], wherein the anodic solution feed stream to the electrochemical cell contains water and hydrogen halide.</u><u style="single">[5]</u><u style="single"> The method of [4], wherein the hydrogen halide comprises at least one of hydrogen bromide or hydrogen chloride.</u><u style="single">[6]</u><u style="single"> The reduction product is alkali metal formate, method [4].</u><u style="single">[7]</u><u style="single"> Conversion of alkali metal formate to alkali metal oxalate by thermal reaction;</u><u style="single"> Accepting alkali metal oxalate in an electrochemically acidified electrolytic cell;</u><u style="single"> Converting alkali metal oxalic acid to oxalic acid and co-producing alkali metal hydroxides, hydrogen, and halogens in an electrochemically acidifying electrolytic cell;</u><u style="single">The method of [6], further including.</u><u style="single">[8]</u><u style="single"> Receiving an anode fluid supply stream containing water and hydrogen halides in the anode fluid region of the electrochemical cell containing the anode;</u><u style="single"> Receiving a supply stream of carbon dioxide gas in the cathode fluid region of an electrochemical cell containing a cathode containing a gas diffusion electrode;</u><u style="single"> Receiving a cathode fluid supply stream containing carbon dioxide and alkali metal bicarbonate in the cathode fluid region of the electrochemical cell;</u><u style="single"> Apply sufficient potential between the anode and cathode of the electrochemical cell to reduce carbon dioxide to alkali metal formate and co-produce halogen.</u><u style="single">A method of reducing carbon dioxide, including.</u><u style="single">[9]</u><u style="single"> The method of [8], wherein the hydrogen halide comprises at least one of hydrogen bromide or hydrogen chloride.</u><u style="single">[10]</u><u style="single"> Conversion of alkali metal formate to alkali metal oxalic acid by thermal reaction;</u><u style="single"> Accepting alkali metal oxalate in an electrochemically acidified electrolytic cell;</u><u style="single"> Converting alkali metal oxalate to oxalic acid and co-producing alkali metal hydroxides, hydrogen, and halogens in an electrochemically acidified electrolytic cell.</u><u style="single">The method of [8], which further comprises.</u><u style="single">[11]</u><u style="single"> First cell compartment;</u><u style="single"> Anode containing a gas diffusion electrode located in the first cell compartment;</u><u style="single"> Second cell compartment;</u><u style="single"> Cathode located in the second cell compartment;</u><u style="single"> Separator between the first cell compartment and the second cell compartment;</u><u style="single">Electrochemical cells including;</u><u style="single"> A hydrogen gas inlet that is connected to the first cell compartment and is configured to supply hydrogen gas to the first cell compartment;</u><u style="single"> Anode fluid inlet that is connected to the first cell compartment and is configured to supply the anodic fluid to the first cell compartment;</u><u style="single"> Cathodic fluid inlet, which is connected to the second cell compartment and is configured to supply the cathodic fluid containing carbon dioxide and alkali metal bicarbonate to the second cell compartment;</u><u style="single"> An energy source that is operably connected to the anode and cathode and is configured to power the anode and cathode to reduce carbon dioxide to reduction products at the cathode.</u><u style="single">A system for reducing carbon dioxide, including.</u><u style="single">[12]</u><u style="single"> The system of [11], wherein the electrochemical cell further comprises an anodic trickle bed solution distributor in the first cell compartment, which is configured to receive the anodic solution from the anodic solution inlet.</u><u style="single">[13]</u><u style="single"> The electrochemical cell further includes a weir-type flow distributor between the anodic solution inlet and the anodic trickle bed solution distributor, which is configured to distribute the anodic solution into the anodic trickle bed solution distributor. [12] System.</u><u style="single">[14]</u><u style="single"> The electrochemical cell further comprises an anode current collector containing a gas plenum configured to receive hydrogen gas from the hydrogen gas inlet, [11] system.</u><u style="single">[15]</u><u style="single"> The system of [14], wherein the gas diffusion electrode of the anode includes at least one flow path in close proximity to the gas plenum of the anode current collector, which is configured to allow hydrogen gas to pass through the gas diffusion electrode of the anode.</u><u style="single">[16]</u><u style="single"> The gas diffusion electrode of the anode includes a carbon cloth portion and a catalyst layer, the system of [15].</u><u style="single">[17]</u><u style="single"> [11] A system that is connected to a second cell compartment and further includes a carbon dioxide gas inlet that is configured to supply carbon dioxide gas to the second cell compartment.</u><u style="single">[18]</u><u style="single"> The system of [17], in which the cathode contains a gas diffusion electrode.</u><u style="single">[19]</u><u style="single"> The system of [18], wherein the electrochemical cell further comprises a cathode trickle bed solution distributor in a second cell compartment, which is configured to receive the cathode fluid from the cathode fluid inlet.</u><u style="single">[20]</u><u style="single"> The electrochemical cell further includes a dam-type flow distributor between the cathode fluid inlet and the cathode trickle bed solution distributor, which is configured to distribute the cathode fluid into the cathode fluid trickle bed solution distributor, [19. ] System.</u><u style="single">[21]</u><u style="single"> The electrochemical cell further comprises a cathode current collector containing a gas plenum configured to receive carbon dioxide gas from the carbon dioxide gas inlet, [18] system.</u><u style="single">[22]</u><u style="single"> The cathodic gas diffusion electrode comprises at least one flow path in close proximity to the gas plenum of the cathode current collector, which is configured to allow carbon dioxide gas to pass through the cathode gas diffusion electrode, [21] system. ..</u></p>