Direct synthesis of hydrogen peroxide in a multicomponent solvent system

Direct synthesis of hydrogen peroxide in a new system

For a multi-component solvent

Full description

Background of the invention

The present invention relates to a process for producing hydrogen peroxide (H2O2) from hydrogen and oxygen. The process uses a reaction solvent, which is a mixture of one or more alcohols, an aliphatic ether with the general formula (I), and optionally water.

Hydrogen peroxide is an important commercial product. It is widely used as a color-reducing powder in the textile and paper industry, as a biocide in the environment and in oxidation processes in the chemical industry. These oxidation processes are represented by processes that use titanium silicalite as catalysts, such as the introduction of an epoxy group into olefins (European Patent No. 100119), the introduction of an ammoximation group into compounds that have carbonyl groups (US Patent No. 4794198), and The oxidation of ammonia into hydroxylamine compounds (US Patent No. 9,081,532) and the introduction of a hydroxylation group onto aromatic compounds compounds (US Patent No. 4,369,783).

The industrial production of aqueous solutions of hydrogen peroxide through a complex process that can be carried out in two stages is well known.

In this process, an anthraquinone solution, such as butylanthraquinone or ethyl anthraquinone, is first hydrogenated in an organic medium that is immiscible with water and then oxidized in air to produce hydrogen peroxide, which is then extracted in the aqueous phase.

However, this process has many disadvantages derived from the necessity of operating with large volumes of reactant chemicals, the necessity of performing numerous steps as well as the relatively high costs of intermediates and the production of ineffective by-products.

Processes for the direct synthesis of hydrogen peroxide from hydrogen and oxygen have been studied to overcome these obstacles. These processes are usually carried out by reacting the two gases in a solvent consisting of an aqueous or aqueous-organic medium, in the presence of a catalytic system consisting of a noble metal, especially platinum group metals or mixtures thereof in the form of salts or supported metals. Among the processes of this type, those that appear particularly attractive from a technical and economic point of view operate in an alcohol or aqueous-alcohol medium, such as in methanol or in methanol-water as described in the patent application. American Patent No. 92 0 4335, in International Patent Application No. 98/16463, in European Patent Application No. 7876 B1, and very specifically in European Patent Application No. 6 97831,

And in the Italian patent application No. MI 2000 A001218, the Italian patent application No. MI 2000 A001219, and the Italian patent application No. MI 2000 A001881.

Keeping other conditions unchanged, higher reaction rates and purity rates are actually observed for operation in aqueous media, and higher reaction performance in turn results in the following:

1- The possibility of carrying out the process under very safe conditions, well outside the scope of the explosion of mixtures of hydrogen and oxygen, and without exposing the process to danger from a technical and economic point of view,

2- The possibility of using fairly low quantities of reinforcing materials (such as halides

halides and acids) in the reaction medium, with beneficial effects on the stability of the catalytic system and on the production of stable hydrogen peroxide solutions.

At a concentration suitable for direct use and economically suitable for oxidation processes

oxidation.

Finally, the concentration of hydrogen peroxide produced can reach commercially useful values, where the boiling point and temperature of vaporization of the alcohol, appropriately selected, are lower than the boiling point and temperature of vaporization of water.

General description of the invention

It has now been discovered that these processes can also be developed from a selectivity and economic point of view, using a system including one or more alcohols, an aliphatic ether and, notably, water, as the solvent for the reaction.

The hydrogen peroxide solutions obtained can be directly used in oxidation processes that use titanium silicalite as a catalyst, where the components of the solvent mixture are compatible with the aforementioned processes. Furthermore, by using this solvent system, the resulting hydrogen peroxide concentration can reach commercially useful values, as the heat of vaporization of suitably eluted ether is lower than that of water and alcohol. In fact, while 9717 calories per mole (equal to about 540 calories per gram) and 8426 calories per mole (equal to 263.3 calories per gram) are respectively necessary to distill water or, for example, methanol, 7290 calories per mole Equivalent to 82.8 calories per gram necessary to distill, for example, methyl-terbutylether.

NTBE).

Accordingly, the subject matter of the present invention relates to a process for producing hydrogen peroxide starting from hydrogen and oxygen, in a reaction solvent containing a halogenated promoter and/or an acidic promoter, in the presence of a catalyst other than

A homogeneous mixture based on one or more metals from the platinum group, where the reaction solvent consists of the following materials:

(1) An alcohol or a mixture of alcohols, and

(2) Aliphatic ether has the general formula (I), and

(3) Water optionally.

Among the alcohols that contain a number of carbon atoms ranging from one carbon atom to six carbon atoms, methanol, ethanol, terbutanol (TBA), or their mixtures are preferred. Methanol is particularly preferred.

Aliphatic ethers are selected from those that have the formula (I):

(R-0-R1 (I

Whereas the same or different R1, R are alkyl groups with a number of carbon atoms ranging from one carbon atom to six carbon atoms. In compounds with the formula (I), it is preferable for R to be methyl, and for R1 to be a trealkyl, in particular using methyl-tert-butyl ether (. (MTBE) The amount of alcohol or mixture of alcohols ranges from 10% by weight to 99.9% by weight for the solvent mixture, and it is preferable that the percentage be from 20% to 80% by weight for the reaction solvent.

The amount of ethers used in the reaction is related to the type of alcohol or alcohols used and generally ranges from 0.1% by weight to 90% by weight, and preferably from 20% by weight to 80% by weight for the reaction solvent, and the amount of water varies when present. From 0 to 50% by weight with respect to the reaction solvent, and preferably from 2% to 30% by weight with respect to the reaction solvent.

According to one embodiment of the process of the present invention, the reaction solvent may also contain one or more hydrocarbons each with a number of carbon atoms ranging from 5 carbon atoms to 32 carbon atoms. These hydrocarbons are usually selected from paraffins, cyclic paraffins, or aromatic compounds. Examples of paraffinic hydrocarbons are preferably selected from those that contain a number of carbon atoms ranging from 5 carbon atoms to 18 carbon atoms, and they can be straight or branched. Examples of the paraffinic hydrocarbons mentioned are n-hexane, n-heptane, n-octane, n-decane, or their branched isomers.

Examples of cyclic paraffinic hydrocarbons include cyclohexane, decaline, or their derivatives that have a replacement with one or more alkyl groups that contain a number of carbon atoms ranging from one carbon atom

One to six carbon atoms. The typical examples of the compounds mentioned are methyl-cyclohexane, ethyl-cyclohexane, or dimethyl-cyclohexane.

Aromatic hydrocarbons suitable for the purposes of the present invention are preferably selected from those containing a number of carbon atoms ranging from 6 carbon atoms to 42 carbon atoms.

Examples of aromatic hydrocarbons include benzene, naphthalene, alkylbenzenes, and alkylnaphthalenes with one or more straight or branched alkyl chains, containing a number of carbon atoms ranging from one carbon atom to 81. A carbon atom, preferably containing a number of carbon atoms ranging from 6 carbon atoms to 12 carbon atoms. Examples of alkylbenzenes are toluene, ortho, meta and para (xylenes), ethylbenzene and cumene. cumene

The amount of hydrocarbons used in the reaction is related to the type of alcohol or alcohols used, and typically ranges from 0.01% to 0.4% by weight, and preferably from 0.1% to 20% by weight, for the total reaction mixture. The catalyst that may be used for the purposes of the invention is a heterogeneous catalyst containing one or more metals from the platinum group as active ingredients. Examples of these metals include palladium, platinum, and ruthenium.

Rhodium, iridium, and gold, and the preferred metals are palladium and platinum.

Palladium is usually found in these catalysts in an amount ranging from 0.1% to 5% by weight, and platinum is found in an amount ranging from 0.01% to 1% by weight, and the atomic ratio between platinum and palladium ranges from 0.1/99.9. To 50/50. Palladium is found preferably in an amount ranging from 0.2% to 3% by weight, and platinum is found in an amount ranging from 0.02% to 0.5% by weight, and the atomic ratio between platinum and palladium ranges from 99/1 to 70/30. In addition to palladium and platinum, there may be other metals, for example, such as ruthenium, rhodium, iridium, and gold, as active ingredients or enhancing materials, in a concentration that usually does not exceed that of palladium. The catalyst can be prepared by dispersing the active components onto an inactive carrier material by precipitation and/or by impregnation, starting from the produced materials, which consist, for example, of solutions of their soluble salts or complexes, and are thus reduced to the metallic state by thermal and/or chemical treatment by reducing materials such as Hydrogen, sodium formiate, or sodium citrate, by means of preparation methods well known in this technical field.

According to an embodiment of the present invention, the catalyst may be prepared by successively dispersing and alternating the materials producing the individual metallic components of the catalyst onto the carrier material as described and stated in the claims of patent application IT MI 2000-A001219. The inactive carrier can typically consist of activated carbon, silica, alumina, silica-alumina, zeolites, and other materials commonly known in the art. Activated carbon is preferred to prepare catalysts useful for invention.

The activated carbon materials that can be used in the invention are selected from materials of fossil or natural origin, and are prepared, for example, from wood, lignite, peat, or coconut, and have a surface area of more than 100 square meters per gram. Preferably a surface area of more than 300 square meters per gram, and carbon that has a surface area of more than 600 square meters per gram is specifically preferred. The preferred activated carbon materials are those with low ash content.

Activated carbon containing a sulfonate group mentioned in European Patent Application No. 978316 can be used in this regard. Before carrying or imbibing the metals, the activated carbon can be subjected to treatment such as washing with distilled water or treatment with acids, bases, or diluted oxidizing agents, such as acetic acid, hydrochloric acid, sodium carbonate, or hydrogen peroxide.

The catalyst is usually dispersed in the reaction medium at a concentration ranging from 0.1% to 10% by weight, and preferably from 0.3% to 3% by weight with respect to the reaction solvent. The acidic catalyst can be any substance capable of generating H+ hydrogen ions in the reaction solvent, and it is generally selected from inorganic acids such as sulfuric acid, phosphoric acid, or nitric acid, or from organic acids such as sulfonic acids. acids. It is preferable to use sulftrric acid and phosphoric acid. phosphoric acid

The acid concentration generally ranges from 20 mg to 1000 mg per kilogram of reaction solvent, and it is preferable for the acid concentration to range from 50 mg to 500 mg per kilogram of reaction solvent.

The halogenated booster can be any material generally capable of generating halide ions from the reaction solvent. Materials capable of generating bromide ions are preferred. These materials are generally selected from hydrobromic acid and its salts that are soluble in the reaction medium, for example sodium bromide, potassium bromide, ammonium bromide, or sodium bromate. It is preferable to use hydrochloric acid, sodium bromide, and potassium bromide.

The concentration of the halogenated booster generally ranges from 0.1 mg to 50 mg per kilogram of reaction solvent, and it is preferable for the concentration of the halogenated booster to range from 1 mg to 10 mg per kilogram of reaction solvent.

The process of producing hydrogen peroxide is carried out by reacting oxygen with hydrogen in the reaction solvent in the presence of the catalyst and reinforcing materials, and in the presence or absence of an inert gas selected from nitrogen, helium, or argon. It is preferable to use nitrogen gas.

The molecular ratio ranges between hydrogen H2 and oxygen O2 in the feed

From 1/1 to 1/100, and it is preferable that the ratio be from 1/2 to 1/15, and the hydrogen concentration in the gas phase in contact with the reaction solvent is maintained at a value less than 4.5% molar, outside the explosion limits of the mixture consisting of Hydrogen H2 hydrogen, oxygen O2, and optionally inert gas

According to an embodiment of the process of the present invention, the reaction may be carried out using air instead of pure oxygen.

The reaction is typically carried out at temperatures between 5°C and 90°C, preferably from 2°C to 50°C, and at a total pressure higher than atmospheric pressure, preferably from 30 bar to 300 bar. The process according to the present invention may be carried out in batches or preferably carried out continuously using a reactor suitable for the purpose selected from those reactors described in the state of the art. Operating under the above conditions, hydrogen peroxide can be produced under safe conditions with reaction yields typically ranging from 30 grams to 200 grams of hydrogen peroxide.

hydrogen peroxide H2O2 (expressed as H2O2 at 100%) per liter of reaction medium each

hour and with molecular selectivity regarding the formation of H2O2 hydrogen peroxide, with reference to the hydrogen consumed, ranging from 60% to 90%. Hydrogen peroxide solutions obtained based on the above can be directly used in oxidation processes that include the use of hydrogen peroxide H2O2 without processing complex intermediate materials such as removing acids and solvents.

Furthermore, the process of the present invention is suitable for producing aqueous solutions of H2O2 hydrogen peroxide for commercial use, by removing organic components from the reaction medium, e.g., by distillation, which can be recycled until the synthesis is accomplished. The process of the present invention allows reactive chemicals to be converted into hydrogen peroxide with large conversions and high selectivities, and to obtain hydrogen peroxide solutions that are free of acids or contain only very small amounts of acidic substances and salts.

Detailed description

The following examples, which have for the sole purpose of describing the present invention in great detail, should in no way be considered limited to the scope of the present invention.

Example 1:

Carrier processing:

50 grams of activated carbon, produced from charcoal from coastal pine trees, in the form of powder (CECA), and 500 milliliters of distilled water, were filled in a one-liter glass bottle. After two hours at 80°C, the activated carbon was filtered and washed with 500 ml of distilled water. The activated carbon, still wet, was then filled into a one-litre flask and after adding 500 ml of the solution to 2 wt% hydrochloric acid (HCl), the temperature was brought to 80°C. After about two hours, the mixture is cooled and the activated carbon is washed over a filter with distilled water until the chlorides are removed. The washed activated carbon is extracted and dried in an oven at a temperature of 120 degrees Celsius.

Example 2:

Catalyst preparation pt/C%Pd-0.l%catalvstl

10 grams of activated carbon, treated as described in Example (1), was filled into a 0.5 liter glass bottle, containing 100 ml of distilled water and 0.32 grams, and the suspension was maintained at room temperature (from 20 °C to 25°C), stirring, for 10 minutes.

10 ml of an aqueous solution containing one gram of Na2PdCI4 solution, at 10% pd, and 0.1 gram of H2ptCl6 solution, at 10% pd, was successively added drop by drop over a period of about 10 minutes.

The suspension was maintained at room temperature for 10 minutes and then heated for 10 minutes to a temperature of 90°C. A solution containing 0.85 grams of sodium formiate in 10 ml of water was then added, and stirring was continued at a temperature of 90 degrees Celsius for two hours.

After cooling to room temperature, the suspension was filtered and the extracted catalyst was washed with distilled water until the chlorides were removed, then dried in an oven at 120°C for two hours.

Example 3 (comparative)

Hydrogen peroxide synthesis

A small experimental laboratory was used, consisting of a sterilization unit made of Hastalloy C alloy with a capacity of 350 ml, equipped with a thermostat control system, a magnetic stirring system by suction, a pressure adjustment and control system during the reaction, and a filter that constantly removes the liquid phase that contains products. The reaction, a feeding system with the mixture of solvent and boosting materials through which the reaction takes place, a feeding system with gaseous chemicals, and a successive set of regulation and control devices. 0.6 grams of catalyst was filled, which was prepared according to the following

In example (1), 100 grams of methanol solution: water (3/97 by weight) containing 6 ppm of HBr and 200 ppm of H2SO4 in the reactor. The pressure of the sterilization unit is adjusted, without stirring, to a pressure of 100 bar using a gas mixture consisting of 3.6% hydrogen H2, 11 oxygen O2, and 85.4% nitrogen N2 by volume. Stirring was then started up to 800 rpm, and the pressure was maintained with a continuous bar of 700 metric liters (liters per hour) of the same gaseous mixture with a simultaneous feeding of 300 grams per hour of a methanol solution. methanol: water with the same composition as It was previously determined to contain 6 ppm HBr and 200 ppm H2SO4.

The temperature inside the reactor is maintained at 8 degrees Celsius. The reaction then proceeds to a continuous decomposition of hydrogen and oxygen in the feed material and at the reactor outlet.

The concentration of hydrogen peroxide that is formed in the liquid reaction stream is determined by titration using potassium permanganate. Selectivity for the converted hydrogen is calculated on the basis of the concentration of hydrogen peroxide in the reaction flow and on the analysis of the hydrogen that leaves the reactor, once the steady state in the reactor is reached. The results obtained are shown in Table (1).

Example 4:

Example (3) was repeated, with the reactor fed with a liquid mixture consisting of 92% methanol, 5% MTBE, and 3% water. This solution contains 6 ppm of HBr and 200 ppm of H2SO4. The results are shown in Table (1).

Example 5:

Example (3) was repeated, with the reactor fed with a liquid mixture consisting of 77% methanol and...

20% MTBE and 3% water. This mixture contains 6 ppm of HBr and 200 ppm of H2SO4. The results are shown in Table (1).

Example 6:

Example (3) was repeated, with the reactor fed with a liquid mixture consisting of 47% methanol and

50% MTBE and 3% water. This solution contains 6 ppm of HBr and 200 ppm of H2SO4. The results are shown in Table (1).

Example 7:

Example (3) was repeated, with the reactor fed with a liquid mixture consisting of 27% methanol and...

70% MTBE and 3% water (percentage by weight of methanol to water = 31.3). This mixture contains 6 ppm of HBr and 200 ppm of H2SO4. Show the results

In Table (1).

Example 8:

Example (3) was repeated, with the reactor fed with a liquid mixture consisting of 17% methanol, 80% MTBE, and 3% water. This mixture contains 6 ppm of HBr and 200 ppm of H2SO4. The results are shown in Table (1).

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Example 9:

Example (3) was repeated, with the reactor fed with a mixture consisting of:

42% methanol, 50% MTBE, 5% cyclohexane, and 3% water. This mixture contains 6 ppm of HBr and 200 ppm of H2SO4. After 50 minutes of reaction, 5.7% of hydrogen peroxide was obtained with a selectivity of 85%.