Process for inhibiting deposition of solids from a gaseous stream obtained from a hydroformylation reaction mixture

[0001] The present invention relates to a method of inhibiting or preventing the deposition of solid material from a gaseous stream. In particular, the present invention relates to a method of inhibiting or preventing the deposition of solid material from a gaseous stream obtained by at least partially degassing the aqueous mixture separated from the reaction mixture from the hydroformylation reaction.

Background of the invention [0002] 1,3-propanediol (PDO) is an industrially important chemical compound. PDO is used as a monomer unit to form polymers, such as poly (trimethylene terephthalate), which are used to make carpets and textiles. PDO is also useful as a coolant for engines, especially in such cooling systems that require coolants with low conductivity and low corrosivity. [0003] PDO can be manufactured industrially by hydroformylation of ethylene oxide under pressure and in the presence of synthesis gas (syngas) (CO and H₂) and a catalyst to produce 3-hydroxypropionaldehyde (HPA) followed by hydrogenation of HPA to PDO. Preferred hydroformylation catalysts are metal carbonyls, in particular cobalt carbonyls. The hydroformylation reaction is usually carried out in a solvent which is inert to the reagents and which dissolves carbon monoxide and a catalyst which is substantially immiscible with water and which has low to medium polarity, so that the HPA hydroformylation product can be extracted from the solvent with water. Such solvents include ethers such as methyl t-butyl ether (MTBE), ethyl t-butyl ether, diethyl ether, phenyl isobutyl ether, ethoxyethyl ether, diphenyl ether, and diisopropyl ether.

[0004] After hydroformylation, HPA is extracted and separated with water from the water-immiscible solvent. The separated aqueous HPA solution is then hydrogenated to form PDO in the presence of a hydrogenation catalyst. The organic phase containing the solvent from the hydroformylation reaction and most of the metal carbonyl catalyst can be recycled (recylculated) for reuse in further hydroformylation.

[0005] The separated aqueous HPA solution can be processed to remove those moieties that adversely affect the operation of the hydrogenation catalyst when converting HPA to PDO. The separated aqueous HPA solution usually contains from 4 to 60% by weight HPA, residual synthesis gas (including carbon monoxide), residual ethylene oxide, and residual metal carbonyl moieties from a hydroformylation catalyst, such as cobalt or rhodium carbonyl moieties, including Co [ What what)₄]₂, What₂(WHAT)₈, and Rh₆(WHAT)₁₆. Most hydrogenation catalysts are poisoned by carbon monoxide (CO) and residual metal carbonyl moieties, so the aqueous HPA solution is treated to remove such catalyst poisons from the solution. U.S. Patent Nos. 5,463,145; US-A-5,463,146; and US-5,786, 524 disclose methods for removing residual hydroformylation catalyzing metals from an aqueous solution from a hydroformylation reaction.

[0006] The aqueous HPA solution can be degassed, oxidized and depleted (depleted) and then contacted with an acidic ion exchange resin to remove these sources of hydrogenation catalyst poisons. The aqueous HPA solution can be degassed, oxidized, and depleted by passing oxygen-containing gas through a column or tank with an aqueous HPA solution - usually in a countercurrent flow setting. The pressure exerted on the aqueous HPA solution in the degassing-oxidizing-exhausting column or reservoir is usually lower than the pressure used in the hydroformylation reaction and in the extraction, so that CO gas is immediately extracted from the aqueous HPA solution in the degassing1

EP 1 846 141 Β1 oxidative-exhausting column or tank, and any residual CO gas is displaced from the solution by an oxygen-containing gas and a stream of any other displacing gas, such as nitrogen. [0007] The oxygen-containing gas also oxidizes the residual metal carbonyl moieties in an aqueous solution, ensuring that the metal moieties are water-soluble, in particular in the presence of by-products in the form of organic acids, such as 3-hydroxypropionic acid, in aqueous HPA. The water-soluble metal moieties are removed from the aqueous HPA solution by contacting the solution with an acidic ion exchange resin.

[0008] The gaseous stream containing degassed CO can be removed from the degassing-oxidizing exhaust gas tank or column to separate CO from the aqueous HPA solution. The gaseous stream removed from the degassing-oxidizing-exhausting device is usually collected and concentrated (condensed) to recover any residual solvent contained therein used in the hydroformylation reaction. The recovery of solvent from the gaseous stream is important to reduce the environmental impact of the process, for example, residual MTBE solvent cannot be released directly into the atmosphere because it is a pollutant according to regulations. The gaseous stream from the degassing-oxidizing-exhausting device can be compressed using a compressor, and the solvent can be recovered by cooling the compressed gas in a cooling tank.

[0009] It has been found that the unexpected deposition of solids from the gas stream inhibits the efficiency of solvent recovery from the gas phase. For example, when gas compression is used for solvent recovery, solids settle in the compressor, thereby causing the compressor to clog. As a result, the compressor only works for a short period of time before it is clogged by settling solid substances. Then degassing-oxidation-depletion and other process steps must be stopped to clean or replace the compressor, which results, in particular, in poor performance / efficiency of the method, especially when conducting a continuous industrial process. In addition, as a result of contamination by deposited solid substances, the compressor is subject to excessive wear. For other solvent recovery configurations, such as for solvent recovery by liquid phase absorption, distillation, low temperature condensation, or solid adsorption, similar impurities can be observed resulting from the deposition of solids from the gaseous stream.

Brief description of the invention [0010] The present invention provides a method of inhibiting or preventing the deposition of solid material from a gaseous stream obtained from an aqueous mixture separated from a reaction mixture from a hydroformylation reaction, comprising separating volatile metal species from the gaseous stream obtained by at least partially degassing the aqueous mixture separated from reaction mixture from a hydroformylation reaction. In one embodiment of the invention, the volatile metal species is separated from the gaseous stream by contacting the gaseous stream with a trap / trap fluid. In another embodiment of the invention, the volatile metal species is separated from the gaseous stream by passing the gaseous stream through a filter having a pore size of 2 pm or less. In yet another embodiment of the invention, the volatile metal species is separated from the gaseous stream by contacting the gaseous stream with a solid adsorbent.

Brief Description of the Drawings [0011] Figure 1 is a schematic representation of a degassing-oxidizing-exhausting column for use in accordance with the method of the present invention.

EP 1 846 141 Β1

Figure 2 is a schematic representation of a degassing-oxidizing-exhausting column and scrubber for use in accordance with the method of the present invention. Detailed description of the invention [0012] The present invention provides a method of inhibiting and / or preventing the deposition of solid material from a gaseous stream obtained by at least partially degassing the aqueous mixture separated from the hydroformylation reaction mixture. The presence in the gaseous stream of a component that settles as a solid at or near ambient temperature and at or near atmospheric pressure is unexpected because the gaseous stream mainly contains carbon monoxide from the aqueous mixture and oxidizing and exhausting gases such as air and nitrogen. It was found that volatile metal species are present in the gaseous stream, and that volatile metal species or their reaction products are deposited as solids from the gaseous stream. The presence of volatile metal species in the gaseous stream in sufficient quantities to deposit significant amounts of solid matter is unexpected also because the gaseous stream is generated from an aqueous mixture containing only very small amounts of metal species, and the metal species remain substantially in the aqueous mixture because the aqueous mixture is degassed , oxidizes, and exhausts to form a gaseous stream. [0013] It has been found that some residual amounts of the metal carbonyl catalyst from the reaction mixture from the hydroformylation reaction that are separated from the aqueous mixture used to extract the reaction mixture from the hydroformylation reaction may accumulate as volatile metal species in the gaseous stream during degassing, oxidation, and depleting the aqueous mixture, and that volatile metal species or their reaction products, will settle as a solid from the gaseous stream. For example, cobalt hydridocarbon (HCo (CO)₄) is a highly volatile compound that, with incomplete oxidation, forms a disproportionate salt of cobalt Co [Co (CO)₄]₂ in the presence of small amounts of acidic co-products from the hydroformylation step, and collected in the gaseous stream removed from the degassing oxidation-exhausting tank, or columns, when the aqueous HPA mixture is degassed, oxidized, and depleted.

[0014] The present invention provides a method for removing one or more volatile metal species, in particular volatile carbonyls and metal hydridocarbonyls, from a gaseous stream obtained by at least partially degassing the aqueous mixture separated from the hydroformylation reaction mixture. The term "volatile metal species" as used herein will be given in the singular, however, it should be understood that the phrase "volatile metal species" is intended to include one or more volatile metal species.

[0015] The aqueous mixture preferably comprises a hydroformylation reaction product and at least one metal moiety from the carbonylation reaction catalyst. Most preferably, the aqueous mixture is an aqueous solution derived from the extraction of the reaction mixture from a hydroformylation reaction with water to separate the hydroformylation reaction product, preferably HPA, from the hydroformylation reaction mixture. The aqueous mixture may be an aqueous solution or an aqueous suspension containing at least 40% by weight of water.

[0016] Volatile metal species can be separated from the gaseous stream by contacting the gaseous stream with a liquid for wet flushing of the gaseous stream, by filtering the gaseous stream through a filter having a pore size of 2 pm or less, or by contacting the gaseous stream with a suitable solid adsorbent , preferably molecular sieves. The gaseous stream from which the volatile metal species have been separated can be further processed without the me3 volatile species

EP 1 846 141 alu1 thallium, or their reaction products, which deposit as a solid from the gaseous stream.

[0017] The aqueous mixture from which the gaseous stream is produced contains metal species from a carbonylation catalyst and a hydroformylation product. In a preferred embodiment of the invention, the metal moiety is a disproportionate metal carbonyl salt, most preferably cobalt and / or rhodium carbonyl and the carbonylation catalyst is metal carbonyl, most preferably cobalt and / or rhodium carbonyl. Most preferably the product of the hydroformylation reaction in the aqueous mixture is HPA.

[0018] The aqueous mixture can be prepared by 1) using a carbonylation catalyst to hydroformylate the unsaturated carbon compound in the presence of synthesis gas in a substantially water-immiscible solvent to produce a water soluble hydroformylation reaction product; 2) extracting the water-soluble hydroformylation reaction product and the metal moiety from the carbonylation catalyst from the solvent by extracting the solvent with an aqueous extractant, which is water or a water-containing solution immiscible with the solvent used in the hydroformylation reaction; and 3) separating the aqueous extractant containing the hydroformylation reaction product and the metal moiety from the solvent to form an aqueous mixture. In the most preferred embodiment of the invention, the unsaturated carbon compound is ethylene oxide (EO) and the hydroformylation reaction product is HPA.

[0019] For hydroformylation of the unsaturated carbon compound, separated or combined feed streams of the unsaturated carbon compound and CO and H₂ (syngas or "syngas") is fed into a hydroformylation vessel, which may be a pressure reaction vessel, such as a bubble column, or a mixing tank operated in portions or continuously. Hydrogen and carbon monoxide will generally be introduced into the reaction vessel in a molar ratio ranging from 1: 2 to 8: 1, respectively, and preferably from 1: 1 to 6: 1. The feed streams are contacted in the presence of a carbonylation catalyst, generally a metal carbonyl, preferably selected from rhodium carbonyl and / or cobalt. The carbonylation reaction catalyst will usually be present in the reaction mixture in an amount in the range of from 0.01 to 1.0% by weight, preferably from 0.05 to 0.5% by weight, based on the weight of the reaction mixture in the hydroformylation reaction.

[0020] The hydroformylation reaction is carried out under conditions effective to produce a hydroformylation reaction product mixture that contains significant amounts of the desired hydroformylation reaction product, wherein the desired hydroformylation reaction product is substantially water soluble. As used herein, the term "substantially water-soluble" means that it is at least 40% by weight dissolved in water. In a preferred embodiment of the invention, the substantially water-soluble hydroformylation reaction product is HPA and the hydroformylation reaction is carried out continuously to form a mixture of a hydroformylation reaction product containing a greater proportion of HPA and a smaller amount of acetaldehyde and PDO, while maintaining the level of HPA in the reaction mixture less than 15% by weight, preferably in the range from 3 to 10% by weight. (For solvents having different densities, the desired concentration of HPA in the reaction mixture can be expressed as the molarity of the solution, i.e. less than 1.5M, preferably in the range of 0.5M to 1M).

[0021] In general, the cobalt carbonyl catalyzed hydroformylation reaction may be carried out at elevated temperatures lower than 100 ° C, preferably 60 ° C to 90 ° C, most preferably 70 ° C to 85 ° C, and the hydroformylation catalyzed by rhodium carbonyl using a temperature about 10 ° C higher. The hydroformylation reaction can generally be carried out at a pressure of 3 to 35 MPa, bar4

EP 1 846 141 dziej1 more preferably (due to the economics of the process) at a pressure of 7 to 25 MPa, with higher pressures being preferred for greater reaction selectivity.

[0022] The hydroformylation reaction is preferably carried out in a liquid solvent inert to the reactants. The term "inert" is intended to mean that no solvent is consumed during the reaction. In general, ideal solvents for the hydroformylation process will dissolve carbon monoxide, be substantially immiscible with water, and exhibit low to medium polarity, so that the hydroformylation reaction product will be dissolved at the desired concentration of at least 5% by weight under the hydroformylation reaction conditions, a significant amount of solvent will remain as the phase separated during extraction with water. The term "substantially immiscible with water" means that the solvent has a water solubility at 25 ° C of less than 25% by weight, such that it forms a separate hydrocarbon-rich phase during the water extraction of the hydroformylation product of the hydroformylation reaction mixture.

[0023] A preferred class of solvents are alcohols and ethers, which can be represented by the following formula:

R2-O-R1 in which R₁, is hydrogen or C_1-20 linear, branched, cyclic or aromatic hydrocarbon or mono- or polyalkenyl oxide and the substituent R₂ means C_1-20 linear, branched, cyclic or aromatic hydrocarbon, alkoxy or mono- or polyalkylene oxide. The most preferred hydroformylation solvents are ethers such as methyl t-butyl ether, ethyl t-butyl ether, diethyl ether, phenylisobutyl ether, ethoxyethyl ether, diphenyl ether and diisopropyl ether. Mixed solvents such as tetrahydrofuran / toluene, tetrahydrofuran / heptane, and t-butyl alcohol / hexane can also be used to obtain the solvent with the desired properties. Currently, the preferred solvent due to the high HPA yield that can be obtained under moderate reaction conditions is methyl t-butyl ether.

[0024] To further increase the yield under moderate reaction conditions, the hydroformylation reaction mixture will preferably contain a catalyst promoter to accelerate the reaction rate. Preferred promoters include lipophilic phosphonium salts and lipophilic amines, which accelerate the rate of hydroformylation without imparting hydrophobicity (water solubility) to the active catalyst. The term "lipophilic" as used herein means that the promoter tends to remain in the organic phase after the water extraction of the reaction mixture from the hydroformylation reaction. The promoter will generally be present in an amount ranging from 0.01 to 1.0 mole per mole of the metal catalyst component (e.g., cobalt or rhodium carbonyl). Currently preferred lipophilic promoters are tetrabutylphosphonium acetate and dimethyldodecylamine.

[0025] At low concentrations, water serves as a promoter for forming the desired carbonyl catalyst moieties. The optimal amounts of water for hydroformylation in methyl t-butyl ether are in the range of 1 to 2.5% by weight. However, excessive amounts of water reduce the selectivity of the desired hydroformylation reaction product below acceptable amounts and can cause the formation of a second liquid phase.

[0026] After the hydroformylation reaction, the hydroformylation reaction mixture comprising a hydroformylation product, preferably HPA, reaction solvent, carbonylation reaction catalyst , residual synthesis gas, residual unsaturated carbon compound, and a minor amount of by-products, is cooled and passed to a reaction vessel for extraction with an aqueous liquid. water

A liquid, generally water, and optionally water miscible solvent, is used to extract the product mixture from the hydroformylation reaction, and is separated from the solvent from the hydroformylation reaction after extraction to produce the aqueous mixture used in the process of the invention.

[0027] The aqueous extraction can be carried out by any suitable means suitable for pressure extraction, such as mixer-settlers, packed or plate extraction columns, or rotary disk contactors. The amount of water added to the extract of the mixture from the hydroformylation reaction will generally be such that a water-mixture ratio ranging from 1: 1 to 1:20, preferably 1: 5 to 1:15 is produced. Extraction with a relatively small amount of water can result in an aqueous mixture containing more than 20% by weight of the hydroformylation product, preferably more than 35% by weight of the hydroformylation product, and more preferably up to 60% by weight of the hydroformylation product, which provides economical hydrogenation of the hydroformylation product.

[0028] The aqueous extraction is preferably carried out at a temperature ranging from 25 ° C to 55 ° C, with lower temperatures being preferred. Importantly, aqueous extraction is carried out under overpressure syngas. Extraction at a partial pressure of carbon monoxide from 0.4 to 7 MPa at 25 ° C to 55 ° C maximizes the retention of the carbonylation catalyst in the organic phase, and minimizes the amount of carbonylation catalyst in the aqueous phase and ultimately in the separated aqueous mixture. Extraction can be carried out at a total pressure of 1 to 25 MPa synthesis gas.

[0029] After extraction, the aqueous phase is separated from the water-immiscible phase - according to conventional liquid-liquid phase separation procedures to form an aqueous mixture containing the hydroformylation reaction product and a metal moiety from the carbonylation reaction catalyst. Preferably, the aqueous mixture will contain the HPA hydroformylation reaction product and minor amounts of cobalt or rhodium carbonyls, or reaction products of cobalt and / or rhodium carbonyls, such as disproportionate salts of cobalt or rhodium carbonyls. The water-immiscible phase will usually retain more carbonylation catalyst from the hydroformylation reaction, and is preferably recycled for further use in the hydroformylation reaction.

[0030] After separating the aqueous mixture containing the hydroformylation reaction product and the metal moiety from the carbonylation catalyst from the water immiscible phase, the aqueous solution may be at least partially degassed, and preferably completely degassed, to produce a gaseous stream containing volatile metal species. The volatile metal moieties are probably derived from the carbonylation catalyst metal moiety. The volatile metal species can be metal carbonyl or metal hydridocarbonyl, and most preferably it is cobalt or rhodium carbonyl or cobalt or rhodium hydridocarbon. The gaseous stream will usually also contain carbon monoxide, synthesis gas, and residual solvent from the hydroformylation reaction previously retained in the aqueous mixture.

[0031] The aqueous mixture can be degassed by reducing the pressure of the aqueous mixture. Preferably, the aqueous mixture is degassed by reducing the pressure of the aqueous mixture during removal of the aqueous mixture from the extraction device, to a pressure below the pressure used during the aqueous extraction. Most preferably, the pressure reduction is large enough to cause the formation of volatile components such as carbon monoxide, volatile metal species, residual solvent residues from the hydroformylation reaction, and any other gases such as residual synthesis gas, and their discharge from the aqueous mixture. In a preferred embodiment of the invention, the extraction is carried out under c16

At a pressure of from 1 to 25 MPa of synthesis gas or carbon monoxide, the aqueous mixture is degassed at a pressure of at most 0.2 MPa, most preferably lower than 0.15 MPa. The flow rate of gas evolved relative to the liquid will depend on the amount of gas dissolved in the aqueous mixture under extraction conditions, with higher pressure resulting in higher dissolved gas concentrations.

[0032] The aqueous mixture can also be depleted when it is degassed for more complete removal of residual carbon monoxide, volatile metal species, and a portion of the residual hydroformylation solvent. The aqueous mixture can be depleted by injecting or bubbling an inert gas into the aqueous mixture to assist in removing other gases from the aqueous mixture. Preferably, the aqueous mixture is exhausted by injecting or bubbling nitrogen gas into the aqueous mixture. Any exhaust gas flow relative to the aqueous liquid flow can be used to improve the removal of dissolved synthesis gas from the aqueous mixture, except as it is removed by "flashing" while reducing pressure. Most typically, a flow ratio of 5-20 mol / hour liquid per mol / hour exhaust gas can be used. In the most preferred embodiment of the invention, the exhaust gas is contacted with the aqueous mixture using a countercurrent flow.

[0033] In a most preferred embodiment of the invention, the aqueous mixture is also preferably treated with an oxidizing agent when it is degassed and depleted. Preferably, the oxidizing agent oxidizes the metal species from the carbonylation catalyst in the aqueous mixture and the volatile metal species in the gaseous stream. Most oxidized metal species present and dissolved in the aqueous mixture can be removed from the aqueous mixture by passing the aqueous mixture through the acidic ion exchange resin before passing the aqueous mixture to the hydrogenerator for hydrogenation. Removal of metal species from the aqueous mixture on the ion exchange resin prevents metal poisoning of the hydrogenation catalyst during the next hydrogenation of the hydroformylation reaction product in the aqueous mixture. Oxidation of volatile metal species in a gaseous stream can make such a compound easier to separate from the gaseous stream.

[0034] In one embodiment of the invention, the aqueous mixture and the gaseous stream may be treated with an oxidizing gas to oxidize metal species from the carbonylation catalyst of the aqueous mixture, and volatile metal species from the gaseous stream. Preferably the oxidizing gas is an oxygen-containing gas, and most preferably the oxidizing gas is air. Also preferably, the aqueous mixture is treated with an oxidizing gas by contacting the aqueous mixture with the oxidizing gas using countercurrent flow. Preferably, the aqueous mixture is treated with an amount of oxidizing gas effective to oxidize as much as possible, and preferably substantially all, of the metal species from the carbonylation catalyst in the aqueous mixture, and as much as possible, and preferably substantially all, of volatile metal species from the gaseous stream degassed from the aqueous mixture. Most preferably, the oxidizing gas is diluted with an inert component, such as nitrogen, to keep the composition outside the ignition limits for the resulting gas mixture. A favorable operation will be to use a flow ratio of 5 - 20 moles / hour of aqueous liquid per mole / hour of combined exhaust and oxidizing gas streams. Oxygen concentrations in the exhaust gas should preferably be less than 5 mole% to avoid flammable compositions.

[0035] In another embodiment of the invention, the aqueous mixture and the gaseous stream may be treated with an oxidizing liquid to oxidize metal species from the carbonylation catalyst of the aqueous mixture and volatile metal species from the gaseous stream. Preferably, the oxidizing liquid is

EP 1 846 141 albo1 or nitric acid or hydrogen peroxide. The aqueous mixture and the gaseous stream may be treated with an oxidizing liquid when using countercurrent flow, or other mixing with the aqueous mixture. Preferably, the aqueous mixture is treated with an amount of oxidizing liquid effective to oxidize as much as possible, preferably substantially all, of the metal species from the carbonylation catalyst in the aqueous mixture, and as much as possible, and preferably as a whole, of volatile metal species from the gaseous stream degassed from the aqueous mixture. In general, this can be accomplished by providing the amount of oxidant in stoichiometric excess relative to all moles of metal moieties present in the aqueous mixture before degassing and depletion.

[0036] Applicants believe that contacting the aqueous mixture with the oxidizing agent causes a small portion of the metal moieties from the carbonylation reaction catalyst present in the aqueous solution to become volatile and enter the gaseous stream. For example, disproportionate cobalt salt Co [Co (CO)₄]₂ may be present in an aqueous mixture of a cobalt carbonylation catalyst used as a hydroformylation catalyst for hydroformylation of ethylene oxide to HPA. The disproportionate cobalt salt is in equilibrium with volatile cobo hydridocarbonyl HCo (CO)₄ in the presence of 3-hydroxypropionic acid, which is present in the aqueous mixture as a by-product of the hydroformylation reaction. The balance is unfavorable for the formation of strongly acid cobalt hydridocarbonyl. Oxidation and depletion of the aqueous mixture in the presence of a stabilizing pressure of degassed carbon monoxide, however, can shift the balance towards the formation of cobalt hydridocarbonyl, allowing the aerobic cobalt hydridocarbonyl to escape from the gaseous stream.

[0037] Temperature can be used to optimize the oxidation of volatile metal species from the gaseous stream. The temperature can be raised during the oxidation step by adding hot water or other means to the stream to accelerate the oxidation of the volatile component. Preferably, the temperature at which the oxidizing agent contacts the aqueous mixture and the gaseous stream is from 50 ° C to 100 ° C to accelerate the oxidation of volatile metal species.

[0038] The aqueous mixture may be degassed, and optionally exhausted and oxidized, in a conventional tank or column, capable of receiving liquid under pressure, venting the gaseous stream as waste gas, and allowing the removal of the degassed aqueous mixture from the column or tank. If, preferably, the aqueous mixture is to be exhausted and oxidized, the reservoir or column must have inlets for injecting exhaust gas, and oxidizing gas or liquid into the aqueous solution.

[0039] Volatile metal species are separated from the gaseous stream produced by degassing the aqueous mixture in an effective manner to inhibit or prevent the deposition of solid material from the gaseous stream after removal of the volatile metal species from the gaseous stream. In a preferred embodiment of the invention, the volatile metal species are separated from the gaseous stream by contacting the gaseous stream with a liquid or solid, and receiving volatile metal species or their reaction products, outside the gaseous stream.

[0040] The liquid or solid for separating volatile metal species from the gaseous stream should be selected to be effective for removing volatile metal species from the gaseous stream. In one embodiment of the invention, an aqueous liquid-retaining liquid in which the volatile metal species are soluble, or from which the volatile metal species will react to form non-gaseous reaction products, is used to separate the volatile metal species from the gaseous stream. Preferably the aqueous retaining liquid is water, and more preferably the aqueous retaining liquid is the aqueous extraction mixture

EP 1 846 141 Β1 reaction mixture from a hydroformylation reaction, which was optionally degassed, oxidized, and depleted. Optionally, the aqueous liquid retaining is an alkaline solution, preferably an alkaline solution, such as potassium hydroxide or sodium hydroxide. Volatile metal hydridocarbonyls, such as cobalt hydridocarbonyl, can be effectively removed from the gaseous stream with water or an aqueous mixture extracted from the reaction mixture from the hydroformylation reaction, and are particularly effectively removed from the gaseous stream with an aqueous basic solution because volatile metal hydridocarbonyls are strongly acidic and react with a base to form salts. Typical flow ratios will include treating 2-100 parts by weight of gas to one part of the trapping liquid.

[0041] In another embodiment of the invention, the liquid organic solvent in which the volatile metal species are soluble is used to separate the volatile metal species from the gaseous stream. Preferably the liquid organic solvent is MTBE. Volatile metal carbonyls that have not been oxidized and are not salts such as cobalt and rhodium carbonyls can be effectively removed from the gaseous stream by MTBE. The organic solvent in which the volatile metal moieties are soluble can be most effectively used to separate volatile metal moieties from the gaseous stream when the aqueous mixture is subjected to only slight oxidation or no oxidation. Typical flow ratios will preferably include treating 2-100 parts by weight of gas with one part of the trapping organic liquid.

[0042] In the most preferred embodiment of the invention, the aqueous mixture from the extraction of the reaction mixture from the hydroformylation reaction - which has optionally been degassed, oxidized and depleted - is used as a liquid stopping agent to separate volatile metal species from the gaseous stream. The aqueous mixture is particularly preferred because it contains a significant amount of organic compounds such that the aqueous mixture can be effective for removing both volatile metal hydridocarbonyls and non-oxidized volatile metal carbonyls from the gaseous stream.

[0043] The gaseous stream containing volatile metal species may be contacted with the liquid retention to separate the volatile metal species from the gas stream by using conventional devices commonly used for contacting and mixing liquid with gas. It is particularly advantageous that the device used for contacting the gaseous stream and the trapping liquid allows operations to be carried out in the presence of solids. Solid substances can form when volatile metal species in a gaseous stream contact liquid, and volatile metal species are separated from the gaseous stream.

[0044] In a preferred embodiment of the invention, a conventional commercially available scrubber with a Venturi orifice (Venturi scrubber) is used to contact the gaseous stream with the retaining liquid to separate volatile metal species from the gaseous stream. Ventiri scrubbers can be designed to receive a wide range of liquid / gas flows, as well as solid substances that can form due to the retention of volatile metal species. Typically, a liquid flow will be scheduled to maintain a solids concentration of less than one percent of the total flow.

[0045] In another preferred embodiment of the invention, a conventional commercially available tray column or packed column is used to contact a gaseous stream containing volatile metal species with a retaining liquid to separate the volatile metal species from the gaseous stream. The flow of the retaining liquid is preferably such that it provides an effective amount to maintain a solids concentration below one percent. The flow of the gaseous stream in the column is preferably reg. 9

EP 1 846 141 l1 is poured to ensure sufficient liquid retention on the shelves or on the filling, allowing effective contact of the gas phase with the retaining liquid. Different sizes of column diameters and shelves or packing allow for simultaneous fulfillment of these conditions when the expected flow rate of volatile metal species is known. Other means for contacting the trapping liquid with the gaseous stream in addition to those described above include spray towers, bubble flow columns, and packed columns.

[0046] In a most preferred embodiment of the invention, the aqueous mixture formed by the aqueous extraction of the reaction mixture from the hydroformylation reaction is used as a liquid trap to separate volatile metal species from the gaseous stream after degassing, depletion, and oxidation of the aqueous mixture. Most preferably, the aqueous mixture is degassed, exhausted, and oxidized in a shelf or packed column, and then recycled through the column to contact the gaseous stream to separate the volatile metal species from the gaseous stream.

[0047] The pressurized aqueous mixture from the extraction of the reaction mixture from the hydroformylation reaction may be provided in the middle between the top and the bottom of the degassing, exhausting, and oxidizing column for degassing, depletion, and oxidation of the aqueous mixture and allowing recycling of the degassed, exhausted and oxidized aqueous mixtures for separating volatile metal species from the gaseous stream. The pressurized aqueous mixture is degassed when entering a lower pressure column. The gas-free gaseous stream generated by degassing the aqueous mixture flows up the column from the central positioned entry area to the top of the column. The degassed aqueous mixture flows from the centrally located entrance area down towards the bottom of the column. Air and nitrogen can be injected into the aqueous mixture in or near the bottom of the column, which is preferably resolved so that air and nitrogen flow up through the column in countercurrent to the downward flowing water mixture. After reaching the bottom, or near the bottom of the column, part of the aqueous mixture - which has been degassed, depleted, and oxidized - can be removed from the column and eluted by an acidic ion exchange resin to remove the oxidized water-soluble metal species contained therein, and then it can be hydrogenated.

[0048] The second part of the degassed, exhausted, and oxidized aqueous mixture may be recycled from the bottom, or near the bottom, column to the top, or near the top, columns where the recycled aqueous mixture flows down through the column from the top or near the top , to the bottom, or near the bottom, columns. The recycled aqueous mixture contacts the upward gaseous stream as the recycled aqueous mixture flows down the column. The recycled aqueous mixture acts as a trap liquid and separates the volatile metal species from the gaseous stream. The gaseous stream can then be removed from the top of the column and treated to separate the residual solvent contained therein from the hydroformylation reaction. After reaching the bottom of the column, the recycled aqueous mixture can be recycled again, or it can be removed from the column by elution through acidic ion exchange resin, and hydrogenated. [0049] In another embodiment of the invention, the volatile metal species may also be separated from the gaseous stream by oxidizing the gaseous stream and mechanically filtering the oxidized gaseous stream in an effective manner to inhibit or prevent the deposition of solid material from the gaseous stream after removing volatile metal species from the gaseous stream . Preferably, the gaseous stream is oxidized by contact with an oxygen-containing gas, preferably air. The filter system can be arranged to be effective for removing most, if not all, of volatile metal species or their reaction products from the oxidized gaseous stream. In one embodiment, the volatile moiety 10

The metal is separated from the gaseous stream by passing the oxidized gaseous stream through a filter having a pore size of 2 pm or less, preferably 1 pm or less. A preferred filter having a pore size of 1 pm or less is a commercially available HEPA filter made of glass wool.

[0050] In a particularly preferred embodiment of the invention, a series of two or more filters is used to separate the volatile metal species from the gaseous stream. The gaseous stream may be passed through a first filter having a pore size of 2 to 4 pm, and then it may be passed through a final filter having a pore size of 1 pm or less, preferably a HEPA submicron filter made of glass wool. Other filters can be used between the first and final filters, with the other filters preferably having a pore size between the pore size of the first filter and the final filter.

[0051] In a preferred embodiment of the invention, the filters are washed at least sporadically by passing a gaseous stream through the filters. Occasional washing is used to clean filters from solid substances that are soluble in the washing liquid and then settle on the filters as a result of the separation of volatile metal species from the gaseous stream. For washing the filters, an aqueous washing solution is preferably used, and most preferably an aqueous alkaline washing solution.

[0052] If a filter is used to separate volatile metal species or their reaction products from the gaseous stream, the filter should be placed very close to the gas outlet from the degassing column or tank through which the gaseous stream exits the degassing column or tank. Placing the filter directly adjacent to the gas outlet from the degassing tank or column allows the separation of volatile metal species or their reaction products on the filter from the gaseous stream without settling of volatile metal species or their reaction products as solids in the connecting lines, or other process components, such as compressors or cold rooms.

[0053] In a most preferred embodiment of the invention, the volatile metal species is separated from the gaseous stream by contacting the gaseous stream with a trapping liquid as described above, and then by passing the gaseous stream through at least one mechanical filter, also as described above.

[0054] In another embodiment of the invention, the volatile metal species can also be separated from the gaseous stream by contacting the gaseous stream with a solid adsorbent effective to adsorb the volatile metal species and / or their reaction products. Preferably, the volatile metal species is separated from the gaseous stream by passing the gaseous stream over an immobilized bed of material effective to adsorb the volatile metal species and / or their reaction products. Silica, alumina or silica-alumina adsorbents, preferably molecular sieves, can be used for this purpose. In a preferred embodiment of the invention, the material used in the fixed bed to adsorb volatile metal species and / or their reaction products are commercially available adsorbents - molecular sieves, the preferred adsorbent is 13Χ molecular sieves. For efficient separation of volatile metal species from the gaseous stream, long-lasting passage of the gaseous stream through the bed length of the adsorbent material is preferable to short-term passage through the bed length. The appropriate bed length can be determined by measuring the amount of volatile metal moieties remaining in the gaseous stream after passing through the bed at a given gas stream flow rate, and adjusting the bed length to a bed length optimized for removing volatile metal species from the gaseous stream.

[0055] Preferably, the gaseous stream is oxidized to oxidize volatile metal species prior to passage

By connecting a gaseous stream through a fixed bed of adsorbent material, thereby increasing the amount of volatile metal species and / or their reaction products that could be adsorbed onto the adsorbent material. The gaseous stream may be oxidized, as described above, by contacting the gaseous stream with an oxidizing agent, such as air or an oxidizing liquid, under conditions that ensure a stoichiometric excess of oxidation is provided relative to the amount of volatile metal species to be removed.

[0056] Temperature can be used to optimize removal of volatile metal species from the gaseous stream. If oxidation does not occur completely, then a lower temperature is advantageous for the next entrapment or adsorption step to cause condensation of the volatile metal species from the gaseous stream to the liquid or to the adsorbent. For example, cobalt hydridocarbonyl has a boiling point of 47 ° C, so it is preferable to use a retaining liquid at or below 40 ° C to separate cobalt hydridocarbonyl from the gaseous stream. In a preferred embodiment of the invention, the cooled trapping liquid is used to separate volatile metal species from the gaseous stream, wherein the cooled trapping liquid preferably has a temperature from 5 ° C to 15 ° C.

[0057] With reference to Figure 1, it shows a preferred embodiment for carrying out the method of the present invention. Carbon monoxide / synthesis gas in the form of an aqueous solution at a pressure of at least 1 MPa, and containing metal species from the carbonylation catalyst, hydroformylation reaction product, carbon monoxide, synthesis gas (syngas), and residual organic solvent may be introduced into the degassing-exhausting-exhausting oxidative (DSO) column 11 through an inlet 13 located in the middle between the top 15 and bottom 17 of the DSO column 11. The aqueous solution is preferably an aqueous extract from the hydroformylation reaction carried out using a carbonylation catalyst, most preferably a cobalt carbonyl catalyst. The DSO column 11 is preferably a shelf or packed column. Column DSO 11 is maintained at a much lower pressure than the incoming aqueous solution - preferably less than 0.15 MPa - so that carbon monoxide, volatile metal species, synthesis gas, and residual organic solvent are ejected from the aqueous solution upon entering column 11 and form a gaseous stream that flows from the inlet 13 towards the top 15 of column 11.

[0058] The DSO column 11 may be filled with an aqueous solution except for the free space at the top 19 near the top 15 of the DSO column 11. The DSO column 11 may have a bottom opening 21 through which the degassed, exhausted and oxidized aqueous solution may exit the DSO column 11. The aqueous solution recycled through feed line 23 may extend from near the bottom 17 to near the top 15 of the DSO 11 column. The aqueous solution entering the DSO 11 column flows from the inlet 13 towards the bottom 17 of the DSO 11 column. At the bottom of column 17 of DSO 11, some of the aqueous solution may come out of the DSO 11 column through the hole in the bottom 21, and some of the aqueous solution may enter recycling via the feed line 23. Pump 25 may be used to pump the aqueous solution through the recycled feed line 23 from near the bottom 17 near the top of column 15 of the column 11. The aqueous solution entering the DSO column 11 from the recycled feed line 23 can then flow through column 11 to the bottom of column 11.

[0059] Air and nitrogen can be injected into the DSO column 11 through through holes (ports) 27 and 29 at the bottom 17 of column 11, respectively. Air, nitrogen, and a gaseous stream flowing up through column 11 are collected in the free space at the top 19, and exits the column 11 through the gas outlet 31. Air and nitrogen flow up countercurrent to the downward stream of aqueous solution, and oxidize and deplete the aqueous solution.

EP 1 846 141 Β1 [0060] The aqueous solution entering the column 11 from the recycle feed line 23 contacts the gaseous stream flowing upwards from the inlet 13 and separates the volatile metal species from the gaseous stream. The aqueous solution entering the column 11 from the recycle feed line 23 is degassed carbon monoxide, synthesis gas, and residual solvent and is rich in oxygen and nitrogen. The aqueous solution entering the column 11 from the recycle feed line 23 acts by oxidizing the gaseous stream flowing upstream of the inlet 13, at least partially oxidizing the volatile metal species. The length of the column from the inlet 13 to the point where the aqueous solution re-enters the column 11 through the recycle feed line is preferably long enough to provide sufficient contact time between the aqueous solution and the gaseous stream to remove substantially all volatile metal species, and their reaction products, from the gaseous stream before the gaseous stream appears in the free space on top 19. [0061] The gaseous stream, oxygen, and nitrogen coming out of the column 11 through the gas outlet 31 are preferably then compressed in a compressor (not shown) and optimally cooled by a cooling brine in a solvent recovery system (not shown) to recover residual solvent present in the gas stream. Gaseous solids deposit less or no deposits in the feed pipes, in the compressor or in the solvent recovery system because the gaseous stream contains less or no volatile metal species and / or their product (s) reaction.

[0062] The aqueous solution coming out of the column, through the hole in the bottom 21, can be passed through a bed with acidic ion exchange resin (not shown) to remove those oxidized metal species that are soluble in the aqueous solution. The aqueous solution may then be introduced into a hydrogenation reactor (not shown) to hydrogenate the hydroformylation reaction product, preferably HPA, to hydrogenate the product, preferably PDO.

[0063] With reference to Figure 2, it shows another preferred embodiment for carrying out the method of the present invention. An aqueous solution under the pressure of carbon monoxide / synthesis gas, at a pressure of at least 1 MPa, containing metal species from the catalyst from the carbonylation reaction, the product of the hydroformylation reaction, carbon monoxide, synthesis gas, and residual organic solvent can be introduced into the degassing-exhausting-oxidizing column (DSO) 33 through an inlet 35 located near the top 37 of DSO column 33. The aqueous solution is preferably an aqueous extract from a hydroformylation reaction carried out using a carbonylation catalyst, most preferably a cobalt carbonyl catalyst. The DSO column 33 is preferably a shelf or packed column. DSO column 33 is preferably maintained at a much lower pressure than the incoming aqueous solution - preferably less than 0.15 MPa - so that carbon monoxide, volatile metal species, synthesis gas, and residual organic solvent rapidly fall out of the aqueous solution as it enters column 11, and they form a gaseous stream that collects in the space at the top 39 near the top 37 of the DSO column 33 and exits the column 33 through the gas outlet 41.

[0064] The DSO column 33 is preferably filled with an aqueous solution except for the space at the top 39. The aqueous solution entering the DSO column 33 flows from the inlet 35 towards the bottom 43 of the DSO column, and exits the column 33 through the hole in the bottom 45. Air and nitrogen they can be injected into the DSO 33 column through the ports (ports) 47 and 49, respectively, at the bottom 43 of the column 33. Air and nitrogen flow upwards through column 33 countercurrently to the flowing aqueous solution, and oxidize and exhaust the aqueous solution. Air and nitrogen collect in the free space at the top 39, together with the gaseous stream, and exit the column 33 through the gas outlet 41, together with ga13

EP 1 846 141 z1 with a jet. Oxygen from air is used to oxidize the gaseous stream when contacting the gaseous stream.

[0065] Air, nitrogen, and gaseous stream are directed directly from the gas outlet 41 to a scrubber with a Venturi scrubber (Venturi scrubber) 51. The cooled water, preferably having a temperature of 10-15 ° C, is also directed directly to the Venturi scrubber 51, in in which the stream of cooled water contacts the gaseous stream, air and nitrogen in the scrubber 51. A stream of cool water separates volatile metal species from the gaseous stream, air, and nitrogen. The gaseous stream, air, and nitrogen are then directed from a Venturi scrubber 51 to a compressor (not shown) and then to a condenser (not shown) in which a cool brine solution is used to separate the residual solvent from the hydroformylation reaction from the gaseous stream. Water, after contact with the gaseous stream, is directed outside the scrubber 51 as a waste water stream and passed through a filter (not shown) to remove solid substances from the water, which can then be recycled to the scrubber 51.

[0066] The aqueous solution coming out of the column 33 through the bottom opening 45 can be passed through a bed of acidic ion exchange resin (not shown) to remove oxidized metal species that are soluble in the aqueous solution. The aqueous solution may then be passed through a hydrogenation reactor to hydrogenate the hydroformylation reaction product, preferably HPA, to hydrogenate the product, preferably PDO.

EXAMPLE 1 [0067] An aqueous solution was prepared by continuous hydroformylation of ethylene oxide with synthesis gas (CO and H2), at a pressure of 7 to 15 MPa, at a temperature of 60 ° C to 100 ° C, in the presence of a dicobaltyl octacarbonyl catalyst in an ether solvent methoxy-t-butyl followed by continuous aqueous extraction of the reaction mixture to form an aqueous solution. The aqueous extraction was carried out at a pressure of 10 MPa and a temperature of 20 ° C to 45 ° C. The aqueous solution contained from 12% to 35% by weight 3-hydroxypropionaldehyde, between 50 and 200 ppm cobalt, and traces of acetaldehyde, MTBE, and 3-hydroxypropionic acid. The aqueous solution was introduced into a degasser vessel, which had a glass sight glass 5.1 cm in diameter by 20.3 cm long placed in half full 200 ml fill. The deaerator pressure was maintained by the synthesis gas released from the aqueous solution during expansion (pressure reduction), and excess gas was vented at the top of the deaerator vessel. The pressure was maintained by means of a pressure transducer, and regulated to 0.2 to 0.3 MPa by means of an automatically controlled valve on the gas phase vent. A separate pressure transducer measured the pressure difference related to the liquid level in the degasser vessel. The liquid level was regulated by a separate control valve at the liquid outlet at the bottom of the vessel.

[0068] The liquid flowed from the degasser vessel to the top shelf of the glass exhaust column, and this column was an uninsulated Oldershaw 10-plate column with a diameter of 5.1 cm, operating at a maximum load of 0.48 cm liquid per shelf. Gas mixture 3% O₂ in N.₂ counter flow to the liquid flow from the bottom of the column, flow 14.2 to 56.6 liters / hour. The aqueous solution was fed to the top of the column and cascaded down the shelves and emerged at the bottom of the column to be directed to the cobalt-removing ion exchange bed. The exhausting column operated at 0.12 to 0.15 MPa total pressure with controlled back pressure on the exhaust gas emerging at the top of the column.

[0069] The degasser and exhausting columns were operated continuously for a period of five weeks, 14

EP 1 846 141 Β1 during this time the upper vent line from the degasser was blocked by a green solid. Analysis of this solid substance showed that the main groups were cobalt. Similar brown-green solids were observed on the top of the Oldershaw glass column above the liquid entry point, and was again analyzed as cobalt.

[0070] These results show that volatile cobalt species are produced during the degassing and depletion of the aqueous solution formed during the aqueous extraction of the mixture from the hydroformylation reaction containing cobalt carbonyl as a catalyst.

EXAMPLE 2 [0071] A direct synthesis of cobalt hydridocarbonyl was carried out, involving the reaction of dicobaltyl octacarbonyl with pyridine to form a disproportionate salt, and the volumetric addition of this salt to sulfuric acid to produce cobalt hydridocarbonyl. Direct synthesis was necessary for the formation of volatile cobalt moieties observed during degassing and depletion of the aqueous extract of the mixture from the cobalt carbonyl catalyzed hydroformylation reaction to test various agents for retaining cobalt volatile moieties.

[0072] 3 grams of dicobalt octacarbonyl was dissolved in 20 grams of pyridine under a nitrogen blanket, allowing degassing of the evolved carbon monoxide. The mixture was introduced into a nitrogen purge burette. The burette was connected to a 250 ml 3-necked flask equipped with an outlet tube and an inlet tube pressed on the tips and immersed near the bottom of the flask. The burette tip and inlet tube are connected through a T-connector. A solution of 25 ml 18M sulfuric acid and 75 ml water was cooled to -17.8 ° C to -15 ° C and then placed in a 250 ml 3-neck flask under a nitrogen jacket, and the flask was immersed in an ice bath. The flask was then flushed with a 2: 1 hydrogen / carbon monoxide mixture ("synthesis gas") at a flow rate of about 300 ml / minute. The dicobalt pyridine / octacarbonyl solution was then added dropwise to the acidic solution in the flask for about 45 to 60 minutes to produce 1.61 to 1.91 g of cobalt hydridocarbonyl.

EXAMPLE 3 [0073] Example 3 was conducted to demonstrate that water, steam, MTBE, DSO column residues, and DSO column residues are effective for separating the cobalt hydridocarbonyl compound from the gaseous stream. The synthesis gas (CO / H2) was purified at a flow of 3-10 ml / min in a 300 ml flask containing cobalt hydridocarbonyl synthesized according to the method described in Example 2 above. A gas stream containing cobalt hydridocarbonyl and synthesis gas was introduced into the first stopping flask through a tube immersed in the stopping flask, arranged to ensure contact between the gas stream and the content of the stopping flask, the content of the first stop flask being either water or methoxy-t-butyl ether or steam at 90 ° C or residue from a DSO column, wherein the DSO column residues were obtained by degassing, depletion, and oxidation of the aqueous extract from the reaction mixture from a 3-hydroxypropionaldehyde hydroformylation reaction containing cobalt carbonyl hydroformylation catalyst. The gaseous stream was then directed from the first stop flask to the second stop flask containing 1N potassium hydroxide solution, a highly effective stop liquid for cobalt hydridocarbonyl. The gaseous stream was injected into the second retention flask through a submerged tube to ensure the contact of the gaseous stream with 1N potassium hydroxide. Air was added to the gaseous stream upstream of the first trap flask when the first trap flask contained water or steam. Nitrogen gas was also added to the gaseous stream before the first stop flask when the first flask

The retention water contained steam. The effectiveness of the tested retention liquids was best assessed by the percentage of cobalt removed in the first retention flask relative to the total amount of cobalt retained in the first and second retention flasks. The results are shown below in Table 1. Table 1

<td>Stopping substance - Trap 1</td><td>Water</td><td>MTBE</td><td>Steam</td><td>Residues from the column DSO</td>

<td>Syngas (ml / min)</td><td> 10</td><td> 3</td><td> 3</td><td> 10</td>

<td>Air (mi / min)</td><td> 10</td><td> 0</td><td> 7.5</td><td> 10</td>

<td>N₂ (Ml / min)</td><td> 0</td><td> 0</td><td> 7.5</td><td> 0</td>

<td>Trap 1 weight of trapped substances in the gangway (g)</td><td> 5</td><td> 5</td><td> 5</td><td> 4</td>

<td>Cobalt retained in Trap 1 (ppm)</td><td> 862</td><td> 9709</td><td> 702</td><td> 970</td>

<td>Cobalt retained Trapie 2 (ppm)</td><td> 365</td><td> 1</td><td> 26</td><td> 36</td>

<td>% What stopped in Trap 1 compared to the sum Traps 1 + 2</td><td> 70.3</td><td> 99.9</td><td> 96.4</td><td> 96.4</td>

[0074] The results show that water is effective to retain cobalt from the oxidized cobalt hydridocarbonyl feed stream with at least 70% efficiency, and that MTBE, DSO column residues, and steam are effective to retain cobalt from the non-oxygenated cobalt hydridocarbonyl feed stream from , approximately, 100% efficiency.

EXAMPLE 4 [0075] Example 4 was carried out to show that mechanical filtration on microfilters is effective for separating the cobalt hydridocarbonyl compound from the gaseous stream. The synthesis gas (CO / H2) was purified at 10 ml / minute in a 300 ml flask containing cobalt hydridocarbonyl synthesized according to the method described above in Example 2. The gas stream containing cobalt hydridocarbonyl and the synthesis gas was passed through a microfilter. The gaseous stream was then introduced from the microfilter into a stopping flask containing a 1N potassium hydroxide solution, a highly effective stopping liquid for cobalt hydridocarbonyl. The gaseous stream was injected into the stopping flask through a submerged tube to ensure contact of the gaseous stream with 1N potassium hydroxide.

Upstream air was added to the gaseous stream. In the first test, the filter was a 2 pm filter. In the second test, the microfilter was glass wool.

[0076] The efficiency of the tested filters was best demonstrated by the percentage of cobalt removed on the filter relative to the total amount of cobalt retained in the stopping flask. The results are shown in Table 2 below.

Table 2

<td>Stopping filter</td><td>2 pm filter</td><td>Glass wool</td>

<td>Syngas (ml / min)</td><td> 10</td><td> 10</td>

<td>Air (ml / min)</td><td> 10</td><td> 10</td>

<td>N₂ (Ml / min)</td><td> 0</td><td> 0</td>

EP 1 846 141 Β1

<td>Stopping filter</td><td>2 pm filter</td><td>Glass wool</td>

<td>Cobalt retained on the filter (ppm)</td><td> 5000</td><td> 650</td>

<td>Cobalt retained on Trapa (ppm)</td><td> 15</td><td> 72</td>

<td>% Co retained on the filter compared to retained on the + filter gangplank</td><td> 99.7</td><td> 90.0</td>

[0077] The results show that microfilters are effective for retaining cobalt from the oxidized cobalt hydridocarbonyl feed stream with at least 90% efficiency.

EXAMPLE 5 [0078] Example 5 was performed to demonstrate that a fixed bed of adsorbent material is effective for separating the cobalt hydridocarbonyl compound from the gaseous stream. The synthesis gas (CO / H2) was purified at 10 ml / min in a 300 ml flask containing cobalt hydridocarbonyl synthesized according to the method described in Example 2 above. The gaseous stream containing cobalt hydridocarbonyl and synthesis gas was directed to a fixed bed of molecular sieves (13Χ) on VHSV, at a flow rate of either 1200 L / hour or 2400 L / hour. Two fixed beds of molecular sieves were used in parallel with a time valve used to divide the flow of gaseous stream between the two beds with intervals of 1 minute. The parallel arrangement of the beds with periodic flow of volatile gas with cobalt through the beds ensured even distribution of cobalt in the beds. Each stationary bed of molecular sieves was 4 cm long, and contained 0.5 g molecular sieves in 0.5 ml volume. The gaseous stream was then directed from the fixed beds of molecular sieves to a stopping flask containing a 1N potassium hydroxide solution, a highly effective liquid stopping cobalt hydridocarbonyl, to measure the penetration of cobalt from the fixed beds. The gaseous stream was injected into the stopping flask through a submerged tube to ensure contact of the gaseous stream with 1N potassium hydroxide. [0079] Two runs were carried out, one measuring the efficiency of volatile cobalt adsorption by fixed beds of molecular sieves (13Χ) when the gaseous stream was not subjected to air oxidation, and the other measuring the same effect when the gaseous stream was subjected to air oxidation. In the oxidation test, air was added to the gaseous stream in front of the fixed beds of molecular sieves.

[0080] The efficiency of stationary molecular sieve beds for separating cobalt from the gaseous stream was measured as a percentage of the cobalt adsorbed on the molecular sieves relative to the cobalt fed in / fed into the gaseous stream. The results are shown below in Table 3.

Table 3

<td></td><td>Synthesis gas (Ml / min)</td><td>VHSV (1 / h)</td><td>Cobalt adsorption on molecular sieves -% feed</td>

<td>Bed 1 - non-oxygenated stream feeding</td><td> 10</td><td> 1200</td><td> 100</td>

<td>Bed 2 - non-oxygenated stream feeding</td><td> 10</td><td> 1200</td><td> 99.1</td>

<td>Bed 1 - oxidized stream feeding</td><td> 10</td><td> 2400</td><td> 100</td>

EP 1 846 141 Β1

<td></td><td>Synthesis gas (Ml / min)</td><td>VHSV (1 / h)</td><td>Cobalt adsorption on molecular sieves -% feed</td>

<td>Bed 2 - oxidized stream feeding</td><td> 10</td><td> 2400</td><td> 100</td>

[0081] The results show that the stationary adsorption bed using molecular sieves is effective for retaining volatile cobalt from both the non-oxidized and the oxidized cobalt hydridocarbonyl feed stream.

EXAMPLE 6 [0082] A hypothetical example (based on predicted results) is derived from the results and conclusions of Examples 1 and 3, illustrating the method according to the present invention. An aqueous solution was prepared by continuous hydroformylation of ethylene oxide with synthesis gas (CO and H₂), at a pressure of 7 to 15 MPa, at a temperature of 60 ° C to 100 ° C, in the presence of a cobalt octacarbonyl catalyst in a solvent of methoxy-t-butyl ether, followed by continuous aqueous extraction of the reaction mixture to form an aqueous solution. The aqueous extraction was carried out at a pressure of 10 MPa, and at a temperature of 20 ° C to 45 ° C. The aqueous solution contained from 12% to 35% by weight of 3-hydroxypropionaldehyde, between 50 and 200 ppm cobalt, and traces of acetaldehyde, MTBE, and 3-hydroxypropionic acid.

[0083] The aqueous solution was passed through a degassing, exhausting, oxidizing column where it was degassed and exhausted with a stream of oxygen and nitrogen gas, under reduced pressure relative to the pressure at which the aqueous solution entered the degassing, exhausting, oxidizing column. The gaseous stream of the exhausted and degassed aqueous solution was introduced into the first stopping flask through a tube immersed in the flask to ensure contact between the gaseous stream and the contents of the stopping flask, where the content of the first flask was either water or methoxy-butyl ether or water vapor at 90 ° C, or residue from the DSO column, where the residue from the DSO column is exhausted and degassed aqueous solution. The gaseous stream was then directed from the first stop flask to the second stop flask containing a 1N potassium hydroxide solution, a highly effective stop liquid for cobalt hydridocarbonyl. The gaseous stream was injected into the second retention flask through a submerged tube to ensure contact of the gaseous stream with a 1N potassium hydroxide solution. The retention efficiency of the medium was measured by comparing the percentage of cobalt removed in the first stop flask relative to the second stop flask. Retention media are effective to retain at least 70% by weight of cobalt from the gaseous stream.