Process for recovering rhodium from a hydroformylation process

Abstract

The present invention generally relates to a process for recovering rhodium from a catalyst purge stream from a C6 or higher olefin hydroformylation process. In one embodiment, the process includes: (a) treating a catalyst-containing liquid purge stream from the hydroformylation process, where the catalyst comprises a noble metal and an organophosphorus ligand, with an oxidizing agent in the presence of a separate liquid aqueous phase comprising a halide-free acid at a temperature sufficient to result in oxidation of a majority of the contained organophosphorus ligand, where the halide-free acid is a C1-C6 organic acid or phosphoric acid; (b) recovering the aqueous phase; (c) contacting the aqueous phase with a separate organic phase by mixing the two phases under a synthesis gas atmosphere, where the separate organic phase comprises the water-insoluble, hydrolyzable organophosphorus ligand and recycled olefins from the hydroformylation process; and (d) separating and returning the recycled organic phase to the hydroformylation process.

Description

[Technical Field]

[0001] The present invention relates to a process for recovering rhodium from a hydroformylation process, and in particular to a process for recovering rhodium from a hydroformylation process comprising producing at least one aldehyde in a reaction zone containing C6 or higher olefins, hydrogen, and carbon monoxide in the presence of a catalyst comprising rhodium and an organophosphorus ligand. [Background technology]

[0002] It is well known that continuous hydroformylation processes slowly form relatively high-boiling aldehyde-derived by-products over time (see, e.g., U.S. Pat. Nos. 4,148,830 and 4,247,486). These "heavies" (defined further below) often function as reaction solvents and therefore initially accumulate in the liquid recycle process, but adjustments in product separation conditions (e.g., temperature, pressure, strip gas flow rate, etc.) are required to prevent their concentration from increasing beyond practical limits. The maximum concentration of heavies that the system can sustain is ultimately determined by establishing the ratio of reactor effluent (feed) introduced into the separation zone to nonvolatile materials returned to the reaction zone (tail) while still maintaining the desired aldehyde production rate. Once the heavies concentration limit is reached, they must be removed at a rate comparable to their formation rate to maintain the desired balance. One common method of heavies removal is volatilization, but if the by-products in question are too high boiling to be distilled overhead (e.g., from higher olefins), it may be necessary to remove them from the system as a liquid purge stream (e.g., removal of the separation zone liquid effluent) to extend catalyst life. Costs, including recovery of rhodium from the liquid purge, are associated with the liquid purge.

[0003] Hydroformylation catalysts containing rhodium and hydrolyzable organophosphorus ligands, such as organomonophosphites, are capable of very high reaction rates (see, for example, "Rhodium Catalyzed Hydroformylation," van Leeuwen, Claver, Kluwer Academic Pub. (2000)). Such catalysts have industrial utility because they can be used to increase the production rate or to efficiently hydroformylate internal and / or branched internal olefins, which react more slowly than linear alpha olefins.

[0004] Accordingly, many processes have been developed for removing and recovering rhodium from streams in hydroformylation processes, such as heavies-bearing liquid purge streams; examples include the use of concentrated phosphoric acid to selectively separate phosphines (see, e.g., U.S. Pat. Nos. 4,242,284 and 4,710,587), the use of membrane or nanofiltration processes (see, e.g., U.S. Pat. Nos. 5,395,979 and 5,681,473), oxidation processes (see, e.g., U.S. Pat. Nos. 4,021,463, 4,196,096, 4,374,278, 4,400,547, 4,528,403, 4,605,780, and 5,290,743), and the like. It would be desirable to have an alternative process for recovering rhodium from hydroformylation processes, particularly in the hydroformylation of higher olefins, which minimizes the introduction of components that interfere with the hydroformylation process. Summary of the Invention

[0005] The present invention advantageously provides a process that, in some embodiments, can enable the recovery of rhodium from a liquid purge stream in a hydroformylation process using a reasonable number of process steps. In some embodiments, such a process can advantageously return a high percentage of rhodium to the hydroformylation process in active form for further use in hydroformylation, rather than sending it to a precious metal recovery operation. In some embodiments, the process of the present invention can advantageously return active rhodium to the hydroformylation process in a manner that minimizes decomposition of the organophosphorus ligand used in hydroformylation.

[0006] In one aspect, a process for recovering rhodium from a catalyst purge stream from a C6 or higher olefin hydroformylation process comprises: (a) treating a catalyst-containing liquid purge stream from a hydroformylation process, wherein the catalyst comprises a noble metal and an organophosphorus ligand, with an oxidizing agent in the presence of a separate liquid aqueous phase comprising a halide-free acid at a temperature sufficient to effect oxidation of a majority of the contained organophosphorus ligand, wherein the halide-free acid is a C1-C6 organic acid or phosphoric acid; (b) recovering the aqueous phase; (c) contacting the aqueous phase with a separate organic phase by mixing the two phases under a synthesis gas atmosphere, the separate organic phase comprising a water-insoluble, hydrolyzable organophosphorus ligand and recycled olefins from the hydroformylation process; (d) separating the recycled organic phase and returning it to the hydroformylation process.

[0007] These and other embodiments are discussed in more detail in the detailed description. DETAILED DESCRIPTION OF THE INVENTION

[0008] All references to the Periodic Table of the Elements and the various Groups therein are to the version published in the CRC Handbook of Chemistry and Physics, 72nd Edition (1991-1992) CRC Press, pages I-11.

[0009] Unless stated to the contrary or implicit from the context, all parts and percentages are by weight and all test methods are as of the filing date of this application. For purposes of United States patent practice, the contents of any referenced patent, patent application, or publication are incorporated by reference in their entirety (or the equivalent United States version thereof is so incorporated by reference), particularly with respect to the disclosure of definitions (to the extent not inconsistent with any definitions specifically provided in this disclosure) and the general knowledge in the art.

[0010] As used herein, "a," "an," "the," "at least one," and "one or more" are used interchangeably. "Comprise," "include," and variations thereof do not have a limiting meaning when these terms appear in the specification and claims. Thus, for example, an aqueous composition containing particles of a hydrophobic polymer can be interpreted to mean that the composition contains "one or more" particles of the hydrophobic polymer.

[0011] As used herein, the term "ppmw" means parts per million by weight.

[0012] For purposes of this invention, the term "hydrocarbon" is intended to include all permissible compounds having at least one hydrogen atom and one carbon atom. Such permissible compounds may also have one or more heteroatoms. In a broad aspect, permissible hydrocarbons include acyclic (with or without heteroatoms) and cyclic, branched and unbranched, carbocyclic and heterocyclic, aromatic and non-aromatic organic compounds, which may be substituted or unsubstituted.

[0013] As used herein, the term "substituted" is intended to include all permissible substituents of organic compounds unless otherwise indicated. In a broad aspect, the permissible substituents include acyclic and cyclic, branched and unbranched, carbocyclic and heterocyclic, aromatic and nonaromatic substituents of organic compounds. Illustrative substituents include, for example, alkyl, alkyloxy, aryl, aryloxy, hydroxyalkyl, aminoalkyl (which can range from 1 to 20 or more carbon atoms, preferably 1 to 12 carbon atoms), as well as hydroxy, halo, and amino. The permissible substituents can be one or more and the same or different for appropriate organic compounds. This invention is not intended to be limited in any manner by the permissible substituents of organic compounds.

[0014] As used herein, the term "hydroformylation" is intended to include, but is not limited to, all permissible hydroformylation processes involving the conversion of one or more substituted or unsubstituted olefinic compounds or a reaction mixture containing one or more substituted or unsubstituted olefinic compounds to one or more substituted or unsubstituted aldehydes or a reaction mixture containing one or more substituted or unsubstituted aldehydes. The aldehydes can be asymmetric or non-asymmetric.

[0015] As used herein, the terms "reaction fluid," "reaction medium," and "catalyst solution" are used interchangeably and may include, but are not limited to, a mixture comprising (a) a metal-organophosphorus ligand complex catalyst, (b) free organophosphorus ligand, (c) aldehyde products formed in the reaction, (d) unreacted reactants, (e) a solvent for the metal-organophosphorus ligand complex catalyst and the free organophosphorus ligand, and, optionally, (f) one or more phosphoric compounds formed in the reaction, which may be dissolved and / or suspended. Reaction fluids may include, but are not limited to, (a) fluids within the reaction zone, (b) fluid streams en route to the separation zone, (c) fluids within the separation zone, (d) recycle streams, (e) fluids withdrawn from the reaction zone or separation zone, (f) withdrawn fluids being treated in an acid removal system such as an extractor or other immiscible fluid contacting system, (g) treated or untreated fluids returned to the reaction zone or separation zone, (h) fluids in external coolers, and (i) ligand decomposition products and constituents derived therefrom, such as oxides, sulfides, salts, oligomers, etc.

[0016] As used herein, the term "spent catalyst" refers to a catalyst comprising a precious metal and an organophosphorus porous ligand that has decomposed or been sufficiently contaminated to be economically usable and must be replaced. In some embodiments, a spent catalyst is a catalyst that has an activity of less than 75% of its initial activity (reaction rate). In some embodiments, a spent catalyst has an activity of less than 50% of its initial activity (reaction rate). Although a liquid purge operation removes a portion of the catalyst to allow fresh catalyst to be added to the remaining catalyst that continues to operate, the purged stream is considered "spent catalyst" because it is not returned to the reactor.

[0017] As used herein, the terms "spent catalyst fluid" and "catalyst-containing liquid purge stream" are used interchangeably and refer to a fluid from a hydroformylation process that includes spent catalyst and may also contain, but is not limited to, a mixture of (a) a noble metal-organophosphorus ligand complex catalyst, (b) free organophosphorus ligand, (c) aldehyde products formed in the hydroformylation reaction, (d) unreacted reactants, (e) a solvent for the metal-organophosphorus ligand complex catalyst and the free organophosphorus ligand, (f) free noble metal and / or clusters containing noble metal, and, optionally, (g) one or more phosphoric acid compounds formed in the reaction, which may be homogeneous or heterogeneous. Additional contaminants may include aldehyde decomposition products (e.g., carboxylic acids or alcohols and aldehyde condensation products), deactivated or poisoned catalyst, process fluids, water, line flushes, etc. As used herein, "liquid purge stream" means a liquid stream in a hydroformylation process that exits the recycle process and is used to remove the accumulation of inerts, impurities, by-products, ligand decomposition products, and other unwanted materials that may otherwise accumulate.

[0018] As used herein, the term "recycled olefins" includes streams recovered after a hydroformylation process or derived from such a stream such that the olefins contained therein have been passed through the hydroformylation process at least once. This stream is typically produced after a product-catalyst separation process, usually as part of downstream purification of the crude aldehyde product. Alternatively, this material may originate after further downstream purification of the alcohol obtained after hydrogenation of the aldehyde (recognizing that the stream at this point may have a very low olefin content). In any case, the "recycled olefins" stream may contain significant levels of aldehydes, hydrocarbons (e.g., hydrogenated olefins), alcohols, and other materials, but preferably has less than 50 wt.% oxygenates, preferably less than 20 wt.% oxygenates, and most preferably less than 5 wt.% oxygenates, each based on the total weight of the stream, and these oxygenates include at least one aldehyde, ester, and / or alcohol derived from the original olefin feed. In some embodiments, "recycled olefins" refers to a stream that has been passed through a hydroformylation process at least once and a product-catalyst separation process at least once, wherein the total amount of aldehydes, esters, and / or alcohols in the recycled olefins is less than 5 weight percent.

[0019] The "recycled olefin" stream exhibits lower reactivity than the original olefin feed to the hydroformylation process, such that the amount of aldehydes formed during syngas processing during step (c) of the recovery process described herein below (contacting an aqueous phase with a separate organic phase by mixing the two phases under a syngas atmosphere, the separate organic phase containing the water-insoluble, hydrolyzable organophosphorus ligand and recycled olefins from the hydroformylation process) is minimized. The lower reactivity is generally due to the reduced level of linear alpha-olefin content (e.g., HC=CH-CH- moieties) in the recycled olefin stream. Examples of these less reactive olefins include isomerized olefins (e.g., internal olefins) or branched olefins (e.g., HC=C(Me)-CH-). The reactivity of olefins and olefin mixtures can be measured by many well-known techniques, for example, by determining the production rate under hydroformylation conditions, which can generally be expressed in units of gmol / L / hr (moles of aldehyde produced per liter of catalyst solution per hour) under a specific set of conditions, such as temperature, catalyst concentration, syngas partial pressure, etc. Under typical conditions with C6 and higher olefins, the more reactive olefins are rapidly consumed, so the recovered unreacted olefins exhibit much lower reactivity and are therefore well suited for use in embodiments of the present invention.

[0020] The term "free ligand" means a ligand that is not complexed with (or bound to) a metal, e.g., metal atom, of a complex catalyst.

[0021] A "hydrolyzable organophosphorus ligand" is a trivalent phosphorus ligand, P, containing at least one PZ bond. (III)PZ is a ligand, and Z is oxygen, nitrogen, chlorine, fluorine, or bromine. Examples include, but are not limited to, phosphites, phosphino-phosphites, bisphosphites, phosphonites, bisphosphonites, phosphinites, phosphoramidites, phosphino-phosphoramidites, bisphosphoramidites, fluorophosphites, and the like. In some embodiments, the ligand is a monodentate hydrolyzable organophosphorus ligand. In some embodiments, the ligand may include a bidentate compound capable of forming a chelate complex with a precious metal and / or may contain multiple PZ moieties, such as polyphosphites, polyphosphoramidites, and the like, as well as mixed PZ moieties, such as phosphite-phosphoramidites, fluorophosphite-phosphites, and the like. In some embodiments, a mixture of ligands may be used.

[0022] As used herein, the terms "heavy by-products" and "heavies" are used interchangeably and refer to by-products from a hydroformylation process having a normal boiling point at least 25° C. higher than the normal boiling point of the desired product of the hydroformylation process (i.e., the desired aldehyde). Such materials are known to form in a hydroformylation process under normal operations due to one or more side reactions, including, for example, by aldol condensation or ligand decomposition. Non-limiting examples of heavies are described, for example, in U.S. Pat. No. 4,148,830.

[0023] As used herein, the term "dimer" refers to a heavy by-product derived from two aldehyde molecules. Similarly, the term "trimer" refers to a heavy by-product derived from three aldehyde molecules.

[0024] As used herein, the terms "isononyl aldehyde" and "mixed C9 aldehydes" are used interchangeably and refer to a fluid composed of two or more aldehyde isomers, each containing nine carbon atoms. Illustrative examples of C9 aldehydes include n-nonanal, 2-methyloctanal, 3-methyloctanal, 4-methyloctanal, 5-methyloctanal, 6-methyloctanal, 7-methyloctanal, 2-ethylheptanal, 2-propylhexanal, 3-propylhexanal, 4,5-dimethylheptanal, 2,3,4-trimethylhexanal, 3-ethyl-4-methylhexanal, 2-ethyl-4-methylhexanal, 2-propyl-3-methylpentanal, 2,5-dimethylheptanal, 2,3-dimethylheptanal, and the like.

[0025] As used herein, the terms "separation zone" and "vaporizer" are used interchangeably and refer to a product-catalyst separation apparatus, such as a distillation apparatus, in which the product aldehyde is vaporized overhead, condensed, and collected, while a non-volatile concentrated effluent (tail or vaporizer tail) containing the homogeneous catalyst is returned to one or more of the reactors. The separation zone temperature is typically higher than the temperature of the hydroformylation reactor and may optionally be operated under reduced pressure. In one embodiment, the vaporizer is characterized by flowing gases of various compositions that aid in product removal and, optionally, catalyst stabilization ("strip gas vaporizer"). Other product-catalyst separation apparatuses include membrane, phase separation, and extraction processes. The nature of the product-catalyst separation apparatus is not critical to the present invention.

[0026] As used herein, the terms "feed to tail" and "feed to tail ratio" are used interchangeably and refer to the mass of reaction fluid entering the separation zone relative to the mass of the separation zone tail exiting the bottom of the separation zone and returning to the hydroformylation reactor. "Feed to tail" is a measure of the rate at which volatiles, such as aldehyde products, are removed from the reaction fluid. For example, a "feed to tail ratio" of 2 means that the weight of reaction fluid entering the separation zone is twice the weight of the condensed effluent returned to the hydroformylation reactor.

[0027] Some embodiments of the present invention relate to a process for recovering rhodium in a hydroformylation process. Such a rhodium recovery process is particularly useful in a hydroformylation process that involves producing at least one aldehyde in a reaction zone, the reaction zone comprising a C6-C aldehyde in the presence of a catalyst. 22 The catalyst comprises an olefin, hydrogen, and carbon monoxide, and the catalyst comprises rhodium and an organophosphorus ligand.

[0028] In some embodiments, a process for recovering rhodium from a catalyst purge stream from a C6 or higher olefin hydroformylation process comprises: (a) treating a catalyst-containing liquid purge stream from a hydroformylation process, wherein the catalyst comprises a noble metal and an organophosphorus ligand, with an oxidizing agent in the presence of a separate liquid aqueous phase comprising a halide-free acid at a temperature sufficient to effect oxidation of a majority of the contained organophosphorus ligand, wherein the halide-free acid is a C1-C6 organic acid or phosphoric acid; (b) recovering the aqueous phase; (c) contacting the aqueous phase with a separate organic phase by mixing the two phases under a synthesis gas atmosphere, the separate organic phase comprising a water-insoluble, hydrolyzable organophosphorus ligand and recycled olefins from the hydroformylation process; (d) separating and returning the recycled organic phase to the hydroformylation process. As used in step (a), a "majority" of the contained organophosphorus ligands means 50% or more by weight of the contained organophosphorus ligands in the liquid purge stream. In the case of ligands having multiple phosphorus atoms per molecule, a "majority" of the contained organophosphorus ligands means 50% or more by weight of all phosphorus atoms in the contained organophosphorus ligands in the liquid purge stream. Quantification of the concentrations of organophosphorus ligands and oxidized organophosphate ligands (e.g., organophosphates) in the liquid purge stream can be achieved by analytical techniques known to those skilled in the art, such as phosphorus NMR and high-performance liquid chromatography (HPLC). HPLC is typically the preferred and therefore the technique used below to determine whether a majority of the contained organophosphorus ligands are oxidized.

[0029] In some embodiments, the noble metal is rhodium and the organophosphorus ligand is a tertiary organophosphorus ligand. In some embodiments, the organophosphorus ligand is a monophosphite. In some embodiments, the oxidizing agent is oxygen, air, oxygen diluted with an inert gas, hydrogen peroxide, an alkyl peroxide, an aryl peroxide, a dialkyl peroxide, a diaryl peroxide, or a peroxyacid having fewer than 9 carbon atoms.

[0030] In some embodiments, following recovery of the aqueous phase in step (b), the process further comprises treating the remaining organic phase from step (a) with water, or with an aqueous solution comprising a halide-free C1-C6 organic acid or phosphoric acid, or with an oxidizing agent in the presence of a separate liquid aqueous phase comprising a halide-free C1-C6 organic acid or phosphoric acid, recovering a second aqueous phase, and combining the second aqueous phase with the aqueous phase of step (b) prior to step (c).

[0031] In some embodiments, the halide-free acid in step (a) is provided in an aqueous solution prior to treating the liquid purge stream, and the aqueous stream contains, in some embodiments, at least 15% by weight of the halide-free acid, in some embodiments, at least 25% by weight of the halide-free acid, and in some embodiments, at least 40% by weight of the halide-free acid. In some embodiments, a mixture of halide-free acids is provided. In some embodiments, the halide-free acid in step (a) is a halide-free C1-C2 organic acid or phosphorous acid. In some such embodiments, a mixture of halide-free C1-C2 organic acids or phosphorous acid is used. Examples of halide-free C1-C2 organic acids that can be used in some embodiments of the present invention include formic acid, acetic acid, glycolic acid, and oxalic acid, with acetic acid being particularly useful.

[0032] In some embodiments, the recycled olefins used in step (c) are from a different hydroformylation process than the catalyst-containing liquid purge stream. In some embodiments, the recycled olefins used in step (c) are from the same hydroformylation process as the catalyst-containing liquid purge stream. The recycled olefins, in some embodiments, are C6 or higher and have a lower hydroformylation activity than the olefin feed used in the hydroformylation process that produces the catalyst-containing liquid purge stream. In some embodiments, the recycled olefins are C6 or higher and have a higher average branching degree than the olefin feed used in the hydroformylation process that produces the catalyst-containing liquid purge stream. Without being bound by theory, it is believed that because the oxidation process may produce organic acids from product aldehydes or heavies, the addition of recycled olefins may help mitigate the effects of high molecular weight acids that tend to form surfactants and emulsions. This may also reduce the amount of halide-free C1-C2 organic acids or phosphorous acid present in the organic phase, which may be useful in the organic phase used in downstream operations and minimize loss of halide-free C1-C2 organic acids or phosphorous acid.

[0033] In some embodiments, the process further comprises washing the organic phase from step (d) with an aqueous wash solution prior to passing the organic phase to the hydroformylation process. In some embodiments, the aqueous wash solution comprises a water-soluble amine. In some embodiments, the water-soluble amine has the following structure: [ka] In the formula, R 1 , R 2 , and R 3 are each independently alkyl and ethoxylate, and R 1 , R 2 , and R 3 and R is an alkyl group. 1 , R2 , and R 3 are ethoxylates, respectively. In some embodiments, the concentration of the amine is 1.5 to 20 weight percent, based on the total weight of the aqueous cleaning solution, and the amount of the amine-containing solution is 2.5 to 50 weight percent of the organic phase. In some embodiments, the water-soluble amine is triethanolamine. In some embodiments, a buffer salt may be used in place of the water-soluble amine; such buffers are described in U.S. Pat. No. 5,741,944 and PCT Publication No. 2013 / 184350. In some embodiments, if the aqueous cleaning solution does not contain a water-soluble amine or a buffer, the decanted bottom aqueous layer may be recycled as part of the initial liquid aqueous phase used in step (a).

[0034] In some embodiments, the process further comprises sparging the aqueous phase with an inert gas or syngas following recovery of the aqueous phase in step (b) and prior to introducing the water-insoluble, hydrolyzable organophosphorus ligand in step (c). In some embodiments, the inert gas comprises nitrogen, argon, helium, or methane.

[0035] In some embodiments, the process of the present invention further comprises returning the organic phase containing the noble metal-organophosphorus complex to the reaction zone in the hydroformylation process. In some embodiments, the process of the present invention further comprises providing the organic phase containing the noble metal-organophosphorus complex to the hydroformylation process before the product-catalyst separation zone so that any residual halide-free C1-C6 organic acid or phosphorous acid can be removed with the product before returning the material to the reaction zone. In some embodiments, the process of the present invention further comprises providing the organic phase containing the noble metal-organophosphorus complex to the hydroformylation process before or in an aqueous extractor, as described in U.S. Pat. No. 5,741,944, before entering the reaction zone.

[0036] Hydrogen and carbon monoxide are required for the process. These may be obtained from any suitable source, including petroleum cracking and refining operations. Syngas mixtures are commonly used as sources of hydrogen and CO.

[0037] As used herein, "syngas" (from synthesis gas) refers to a gas mixture containing varying amounts of CO and H. Production methods are well known and include, for example, (1) steam reforming and partial oxidation of natural gas or liquid hydrocarbons and (2) gasification of coal and / or biomass. Hydrogen and CO are typically the major components of synthesis gas, but synthesis gas may also contain carbon dioxide and inert gases such as CH, N, and Ar. The molar ratio of H to CO can vary widely but generally ranges from 1:100 to 100:1, preferably 1:10 to 10:1. Synthesis gas is commercially available and is often used as a fuel source or as an intermediate for the production of other chemicals. The most preferred H:CO molar ratio for chemical production is 3:1 to 1:3, with a ratio of about 1:2 to 2:1 typically targeted for most hydroformylation applications.

[0038] Olefin starting reactants that can be used in the hydroformylation process of the present invention include both optically active (prochiral and chiral) and optically non-active (achiral) olefinically unsaturated compounds containing 6 to 22, preferably 8 to 22, and more preferably 8 to 20 carbon atoms. Such olefinically unsaturated compounds can be substituted or unsubstituted, terminally or internally unsaturated, linear, branched, or cyclic. Olefin mixtures such as those obtained from the oligomerization of propene, butene, isobutene, and the like (e.g., so-called dimeric, trimeric, or tetrameric butenes, as disclosed in U.S. Pat. Nos. 4,518,809 and 4,528,403) can be used. Furthermore, such olefinic compounds can further contain one or more additional ethylenically unsaturated groups, and mixtures of two or more different olefinically unsaturated compounds can be used as the starting hydroformylation material, if desired. For example, commercially available alpha-olefins containing 8 or more carbon atoms may contain small amounts of corresponding internal olefins and / or their corresponding saturated hydrocarbons, and such commercially available olefins do not necessarily need to be purified from them before being hydroformylated. Exemplary mixtures of olefinic starting materials that can be used in the hydroformylation reaction include, for example, mixed butene dimers and trimers. Furthermore, such olefinically unsaturated compounds and the corresponding aldehyde products derived therefrom may also contain one or more groups or substituents that do not unduly adversely affect the hydroformylation process or the process of the present invention, as described, for example, in U.S. Pat. Nos. 3,527,809 and 4,769,498.

[0039] Embodiments of the present invention are particularly useful for the production of non-optically active aldehydes by hydroformylating achiral alpha-olefins containing from 6 to 22, preferably from 8 to 20, carbon atoms, and achiral internal olefins containing from 8 to 20 carbon atoms, as well as starting material mixtures of such alpha-olefins and internal olefins.

[0040] Exemplary alpha and internal olefins include, for example, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, 2-heptene, 2-octene, propylene dimer, propylene trimer, propylene tetramer, 2-ethyl-1-hexene, and mixtures thereof.

[0041] A solvent is advantageously employed in the hydroformylation process. Any suitable solvent that does not unduly interfere with the hydroformylation process can be used. For example, solvents suitable for rhodium-catalyzed hydroformylation include those disclosed in, for example, U.S. Patent Nos. 3,527,809, 4,148,830, 5,312,996, and 5,929,289. Non-limiting examples of suitable solvents include saturated hydrocarbons (alkanes), aromatic hydrocarbons, water, ethers, polyesters, alkylated polyethers, aldehydes, ketones, nitriles, alcohols, esters, and aldehyde condensation products. Specific examples of solvents include tetraglyme, pentane, cyclohexane, heptane, benzene, xylene, toluene, diethyl ether, tetrahydrofuran, butyraldehyde, and benzonitrile. The organic solvent may also contain dissolved water up to the saturation limit. Exemplary solvents that can be used in the production of aldehydes include ketones (e.g., acetone and methyl ethyl ketone), esters (e.g., ethyl acetate, di-2-ethylhexyl phthalate, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate), hydrocarbons (e.g., toluene), nitrohydrocarbons (e.g., nitrobenzene), ethers (e.g., tetrahydrofuran (THF)), and sulfolane. In rhodium-catalyzed hydroformylation, it may be desirable to use as the primary solvent the aldehyde compound corresponding to the aldehyde product desired to be produced and / or a high-boiling aldehyde liquid condensation by-product, which may be produced in situ during the hydroformylation process, as described, for example, in U.S. Pat. Nos. 4,148,830 and 4,247,486. Indeed, although any suitable solvent can be used at the start of a continuous process if desired, the primary solvent will usually ultimately comprise both the aldehyde product and the high-boiling aldehyde liquid condensation by-product (heavies), due to the nature of the continuous process. The amount of solvent is not particularly critical, provided it is sufficient to provide the desired transition metal concentration in the reaction medium. Typically, the amount of solvent ranges from about 5 weight percent to about 95 weight percent, based on the total weight of the reaction fluid. Mixtures of two or more solvents may also be used.

[0042] The hydroformylation reaction involves a solvent as described in the previous paragraph, although other solvents may be used in the process of the present invention.

[0043] Prior to or during treatment with the oxidizing agent described in step (a) of the present invention, additional solvents may optionally be added, especially if the purge stream is particularly viscous. In such embodiments, these solvents should be of low polarity, such as C or higher olefin feed, recycled olefin streams, hydrocarbons (e.g., hexane, heptane), aromatic hydrocarbons (e.g., toluene, xylene), etc. Oxygen-, halogen-, or nitrogen-containing solvents are preferably not added in this step.

[0044] The solvent used in step (d) of the present invention is different from the solvent used in the hydroformylation process and is referred to herein as a "recovery solvent." The recovery solvent, as defined herein, comprises at least 50% recycled olefins. Preferably, the recovery solvent comprises at least 70%, and most preferably greater than 90%, recycled olefins to which a hydrolyzable organophosphorus ligand has been added. Additional solvent, such as that used in the hydroformylation process (described above), and / or fresh olefin feed may also be used as part of the recovery solvent.

[0045] Catalysts useful in hydroformylation processes include catalysts or precious metals. Precious metals can include Group 8, 9, and 10 metals selected from rhodium (Rh), cobalt (Co), iridium (Ir), ruthenium (Ru), iron (Fe), nickel (Ni), palladium (Pd), platinum (Pt), osmium (Os), and mixtures thereof. Preferred metals are rhodium, cobalt, iridium, and ruthenium, and more preferably rhodium, cobalt, and ruthenium, especially rhodium. The initial active metal can be delivered to the hydroformylation reaction system as a catalyst precursor or as an activated catalyst, as described in U.S. Pat. No. 6,700,021. Embodiments of the present invention are particularly well suited for the recovery of rhodium, as in some embodiments, the catalyst or precious metal is rhodium.

[0046] The number of available coordination sites on such metals is well known in the art. Thus, the catalytic species, which may comprise a complex catalyst mixture, may include monomeric, dimeric, or higher nuclei forms, preferably at least one organophosphorus-containing molecule complexed per molecule of metal, e.g., rhodium.

[0047] Catalysts, as well as methods for their preparation, are well known in the art and include those disclosed in the above-mentioned patents. Generally, such catalysts consist essentially of a metal in complex combination with an organophosphorus ligand. Carbon monoxide is also present and is believed to be complexed with the metal in the active species. The active species may also contain hydrogen bonded directly to the metal.

[0048] Acceptable organophosphorus ligands that comprise the metal-organophosphorus ligand complex and free organophosphorus ligand include mono-, di-, and triorganophosphites. Other organophosphorus ligands than those mentioned above may also be used. Mixtures of such ligands may be used in the metal-organophosphorus ligand complex catalyst and / or the free ligand, as desired, and such mixtures may be the same or different. The present invention is not intended to be limited in any manner by the acceptable initial organomonophosphite ligands or mixtures thereof. It should be noted that successful practice of the present invention does not depend on or presuppose the exact structure of the initial metal-organophosphorus ligand complex species, which may exist in mononuclear, binuclear, and / or higher nuclear forms. In fact, the exact structure is unknown. While not intending to be bound by any theory or mechanistic theory, it is believed that the catalytic species, in its simplest form, consists essentially of the metal in complex combination with the organophosphorus ligand and carbon monoxide and / or hydrogen. During oxidation step (a), the organophosphorus ligands are converted to their oxides and removed from the metal-organophosphorus ligand complex. Thus, the nature of the initial organophosphorus ligands is not critical to the present invention, as they are destroyed in step (a).

[0049] The oxidation conditions in step (a) in some embodiments of the process of the present invention are selected to provide substantial, and preferably complete, oxidation of the organophosphorus ligands present, while minimizing oxidation of any residual aldehydes present. The nature of the oxidizing agent and organophosphorus ligand, the reaction time, and the reaction temperature affect the rate and extent of oxidation of the organophosphorus ligands. Some guidance regarding the selective oxidation of organophosphorus ligands is provided, for example, in U.S. Pat. No. 4,605,780. The progress of the oxidation can be monitored by high pressure liquid chromatography, gas chromatography, or other methods. 31 The amount of organic acid formed can be easily monitored by a variety of common analytical techniques, such as P NMR. Excessive oxidizing conditions should be avoided to minimize oxidation of residual aldehyde products contained in the organic phase to the corresponding carboxylic acids. The amount of organic acid formed can also be monitored by conventional means, such as gas chromatography.

[0050] In some embodiments, the mixture should be thoroughly mixed during the oxidation in step (a) to allow the liberated precious metals to migrate from the organic phase to the aqueous phase. However, it is important that the resulting phases separate easily to facilitate recovery of the aqueous phase. Therefore, it is desirable to minimize the polarity of the organic phase by minimizing the amount of polar organic compounds (e.g., oxygen-, nitrogen-, and halide-containing organic compounds). Minimizing the content of aldehydes and higher acids (C6 and higher) in the organic phase is important for embodiments of the present invention. This can be achieved by removing as much of the aldehyde product as possible prior to the oxidation in step (a), for example, by using a product-catalyst separation unit. If an additional solvent is added in step (a) to reduce viscosity, the solvent should generally be selected to contain minimal amounts of oxygen-, nitrogen-, and halide-containing organic compounds.

[0051] The hydrolyzable organophosphorus ligand added in step (c) is preferably insoluble in water (in some embodiments, 0.1 wt. % or less in water, in some embodiments, 0.01 wt. % or less in water, preferably 0.001 wt. % or less in water). The resulting catalyst solution in the organic phase can then be added to a hydroformylation process using a different ligand, including a mixture of hydrolyzable and non-hydrolyzable ligands. The ligand added in step (c) is preferably the ligand used in the original hydroformylation process that produced the initial purge stream, although the recovered catalyst solution can be used in a different hydroformylation process unit.

[0052] As used herein, the term "complex" refers to a coordination compound formed by the combination of one or more electronically rich molecules or atoms with one or more electronically poor molecules or atoms, each of which can exist independently. Carbon monoxide, properly classified as a ligand, may be present and coordinated to the metal. The final composition of the complex catalyst may also contain additional ligands, such as hydrogen or anions, to fill the coordination sites or nuclear charge of the metal. Exemplary additional ligands include, for example, alkyl, aryl, substituted aryl, acyl, CN, (R)PO, and RP(O)(OH)O (where each R is the same or different and is a substituted or unsubstituted hydrocarbon radical, e.g., alkyl or aryl), acetate, acetylacetonate, SO, PF, PF, NO, NO, CH, CH=CHCH, CHCH=CHCH, CHCN, CHCN, NH, pyridine, (C2H5)N, mono-, di-, and tri-olefins, tetrahydrofuran, and the like. The complex species preferably does not contain any additional organic ligands or anions that may poison the catalyst or adversely affect catalytic performance. In metal-organophosphite ligand complex catalyzed hydroformylation reactions, it is preferred, although not absolutely necessary, that the active catalyst does not contain halogens and sulfur directly bonded to the metal.

[0053] Organophosphorus compounds that may function as ligands for metal-organophosphorus ligand complex catalysts and / or free ligands can be of the achiral (optically inactive) or chiral (optically active) type and are well known in the art. Achiral organophosphorus ligands are preferred.

[0054] Such organophosphorus ligands and / or methods for their preparation are well known in the art and include, for example, organophosphate ligands. As used herein, an "organomonophosphite ligand" is a compound containing a single phosphorus atom bonded to three oxygen atoms, each of which is further bonded to a carbon moiety. Illustrative examples include, but are not limited to, monoorganophosphite, diorganophosphite, and triorganophosphite compounds, such as tris(2,4-di-t-butylphenyl)phosphite, 4,8-di-tert-butyl-6-(2-(tert-butyl)-4-methoxyphenyl)-2,10-dimethoxydibenzo[d,f][1,3,2]dioxaphosphepine, and the like.

[0055] Representative monoorganophosphites may include those having the formula: [ka] In the formula, R 10 represents a substituted or unsubstituted trivalent hydrocarbon radical containing 4 to 40 or more carbon atoms, e.g., trivalent acyclic and trivalent cyclic radicals, e.g., trivalent alkylene radicals such as those derived from 1,2,2-trimethylolpropane, or trivalent cycloalkylene radicals such as those derived from 1,3,5-trihydroxycyclohexane. Such monoorganophosphites can be found, for example, in U.S. Pat. No. 4,567,306, which describes them in more detail.

[0056] Representative diorganophosphites may include those having the formula: [ka] In the formula, R 20 represents a substituted or unsubstituted divalent hydrocarbon radical containing from 4 to 40 or more carbon atoms, and W represents a substituted or unsubstituted monovalent hydrocarbon radical containing from 1 to 36 or more carbon atoms.

[0057] Representative substituted and unsubstituted monovalent hydrocarbon radicals represented by W in formula (II) above include alkyl and aryl radicals, and R 20 Representative substituted and unsubstituted divalent hydrocarbon radicals represented by include divalent acyclic radicals and divalent aromatic radicals. Exemplary divalent acyclic radicals include, for example, alkylene, alkylene-oxy-alkylene, alkylene-S-alkylene, cycloalkylene radicals, and alkylene-NR 24 -alkylene, wherein R 24 is hydrogen or a substituted or unsubstituted monovalent hydrocarbon radical, e.g., an alkyl radical having 1 to 4 carbon atoms. More preferred divalent acyclic radicals are divalent alkylene radicals, such as those disclosed more fully in U.S. Pat. Nos. 3,415,906 and 4,567,302. Exemplary divalent aromatic radicals include, for example, arylene, bisarylene, arylene-alkylene, arylene-alkylene-arylene, arylene-oxy-arylene, arylene-NR 24 -arylene, wherein R 24 is as defined above, such as arylene-S-arylene, and arylene-S-alkylene. More preferably, R 20 is a divalent aromatic radical as more fully disclosed in, for example, U.S. Pat. Nos. 4,599,206, 4,717,775, and 4,835,299, and PCT Publication WO2016087301.

[0058] Representative of a more preferred class of diorganophosphites are those of the formula: [ka] wherein W is as defined above, each Ar is the same or different and represents a substituted or unsubstituted aryl radical, each y is the same or different and has a value of 0 or 1, and Q is -C(R 35 )2-, -O-, -S-, -NR 36 -, Si(R 37)2, and —CO—, and each R 35 are the same or different and represent hydrogen, alkyl radicals having 1 to 12 carbon atoms, phenyl, tolyl, and anisyl; R 36 is as defined above, and each R 37 are the same or different and represent hydrogen or a methyl radical, and m has a value of 0 or 1. Such diorganophosphites are described in more detail, for example, in U.S. Pat. Nos. 4,599,206, 4,717,775, and 4,835,299, and PCT Publication WO 2016 / 087301.

[0059] Representative triorganophosphites may include those having the formula: [ka] In the formula, each R 46are the same or different and are substituted or unsubstituted monovalent hydrocarbon radicals, such as alkyl, cycloalkyl, aryl, alkaryl, and aralkyl radicals, which may contain from 1 to 24 carbon atoms. For example, exemplary triorganophosphites include, for example, trimethyl phosphite, triethyl phosphite, butyl diethyl phosphite, tri-n-propyl phosphite, tri-n-butyl phosphite, tri-2-ethylhexyl phosphite, tri-n-octyl phosphite, tri-n-dodecyl phosphite, dimethylphenyl phosphite, diethylphenyl phosphite, methyl diphenyl phosphite, ethyl diphenyl phosphite, triphenyl phosphite, trinaphthyl phosphite, bis(3,6,8-tri-t-butyl-2-naphthyl)methyl phosphite, bis(3,6,8-tri-t-butyl-2- The organic phosphites include trialkyl phosphites, dialkylaryl phosphites, alkyl diaryl phosphites, triaryl phosphites, etc., such as tris(2,4-di-t-butylphenyl) phosphite, tris(3,6-di-t-butyl-2-naphthyl) phosphite, bis(3,6,8-tri-t-butyl-2-naphthyl)cyclohexyl phosphite, tris(3,6,8-tri-t-butyl-2-naphthyl)(4-biphenyl) phosphite, bis(3,6,8-tri-t-butyl-2-naphthyl)phenyl phosphite, bis(3,6,8-tri-t-butyl-2-naphthyl)(4-benzoylphenyl) phosphite, bis(3,6,8-tri-t-butyl-2-naphthyl)(4-sulfonylphenyl) phosphite, etc. The most preferred triorganophosphite is tris(2,4-di-t-butylphenyl) phosphite. Such triorganophosphites are described in more detail, for example, in U.S. Pat. Nos. 3,527,809 and 4,717,775, and U.S. Publication No. US20150336093.

[0060] If necessary, supplemental or additional organomonophosphite ligand can be supplied to the reaction medium of the hydroformylation process at any time and in any suitable manner, for example, to maintain a predetermined level of free ligand in the reaction medium.

[0061] The use of aqueous buffer solutions to prevent and / or reduce hydrolysis of organophosphorus ligands and deactivation of metal-organophosphorus ligand complexes is disclosed in U.S. Pat. No. 5,741,942. The aqueous buffer solutions used in U.S. Pat. No. 5,741,944 are generally salts of weak acids or weak bases, usually Group 1 or Group 2 metal (e.g., Na, K, Ca) salts of weak acids. In some cases, amines are used, which generate ionic salts, such as ammonium salts, when they neutralize and remove at least some of the phosphoric acid compounds from the reaction fluid. Aqueous buffer solutions usable in the present invention can include any suitable buffer mixture containing salts of oxyacids, the nature and proportions of which in the mixture are such that the pH of the aqueous solution can range from 3 to 9, preferably 4 to 8, and more preferably 4.5 to 7.5. In this regard, suitable buffer systems can include a mixture of anions selected from the group consisting of phosphate, carbonate, citrate, maleate, fumarate, and borate compounds, and a cation selected from the group consisting of ammonium and alkali metals, such as sodium and potassium. Such buffer systems and / or methods for their preparation are well known in the art. It is preferred to use a buffer extractor, especially on recovered rhodium-containing streams, to remove acids or other impurities before returning them to the reaction system.

[0062] The hydroformylation product may be asymmetric, non-asymmetric, or a combination thereof, with non-asymmetric being preferred. The process may be carried out in any batch, continuous, or semi-continuous mode, and may include catalyst liquid and / or gas recycle operations as desired.

[0063] The recycle procedure generally involves continuously or intermittently withdrawing a portion of the liquid reaction medium containing the catalyst and aldehyde product from the hydroformylation reactor, i.e., reaction zone, and recovering the aldehyde product therefrom by distillation (e.g., vaporization separation) using a composite membrane as disclosed in U.S. Patent Nos. 5,430,194 and 5,681,473, or, as appropriate, in one or more stages under atmospheric, reduced, or elevated pressure in a separate distillation zone, with the non-volatile metal catalyst-containing residue being recycled to the reaction zone, as disclosed, for example, in U.S. Patent No. 5,288,918. Condensation of the volatile materials and their separation and further recovery, for example, by further distillation, can be carried out in any conventional manner, the crude aldehyde product can be passed for further purification and isomer separation, if desired, and any recovered reactants, such as the olefinic starting material and synthesis gas, can be recycled to the hydroformylation process (reaction zone or reactor) in any desired manner. The recovered metal catalyst containing raffinate of such membrane separation or the recovered non-volatilized metal catalyst containing residue of such vaporization separation can be recycled to the hydroformylation process (reaction zone or reactor) in any conventional manner desired.

[0064] In addition to the other components discussed herein, the hydroformylation reaction mixture compositions usable herein can, and usually do, contain small amounts of additional components, such as those intentionally used in the hydroformylation process or formed in situ during the process. Examples of such components that may also be present include unreacted olefin starting material, carbon monoxide and hydrogen gas, and in situ-formed products, such as saturated hydrocarbons and / or unreacted isomerized olefins corresponding to the olefin starting material, ligand decomposition compounds, and high-boiling liquid aldehyde condensation by-products, polymeric catalyst stabilizers described in U.S. Pat. No. 4,774,361 and PCT Publication No. 2019 / 112866, and other inert cosolvent-type materials or hydrocarbon additives, if used.

[0065] The reaction conditions for the hydroformylation process encompassed by embodiments of the present invention can include any suitable hydroformylation conditions previously used to produce optically active and / or non-optically active aldehydes. For example, the total gas pressure of the hydrogen, carbon monoxide, and olefin starting compounds in the hydroformylation process can range from 1 to 69,000 kPa. However, it is generally preferred to operate the process at a total gas pressure of the hydrogen, carbon monoxide, and olefin starting compounds of less than 14,000 kPa, more preferably less than 3,400 kPa. The minimum total pressure is primarily limited by the amount of reactants required to obtain the desired reaction rate. More specifically, the carbon monoxide partial pressure in the hydroformylation process of the present invention is preferably 1 to 6,900 kPa, more preferably 21 to 5,500 kPa, and the hydrogen partial pressure is preferably 34 to 3,400 kPa, more preferably 69 to 2,100 kPa. Generally, the H2:CO molar ratio of gaseous hydrogen to carbon monoxide in the reaction zone can range from 1:10 to 100:1 or more, with a more preferred hydrogen to carbon monoxide molar ratio being from 1:10 to 10:1.

[0066] Generally, the hydroformylation process can be carried out at any operable reaction temperature. Advantageously, the hydroformylation process is carried out at a reaction temperature of from -25°C to 200°C. Generally, hydroformylation reaction temperatures of from 50°C to 120°C are preferred for all types of olefinic starting materials. The hydroformylation reaction conditions used will depend on the type of aldehyde product desired.

[0067] The hydroformylation process of the present invention can be carried out using one or more suitable reactors, such as, for example, a fixed-bed reactor, a fluidized-bed reactor, a tubular reactor, a Venturi reactor, a bubble column reactor, a continuously stirred tank reactor (CSTR), or a slurry reactor. The optimal size and shape of the reactor will depend on the type of reactor used. As discussed further below, the hydroformylation process can comprise one or more reaction zones, one or more separation zones, and one or more buffer treatment zones. The reaction zone used in the present invention can be a single vessel or can comprise two or more separate vessels. The separation zone used in the present invention can be a single vessel or can comprise two or more separate vessels. The buffer treatment zone used in the present invention can be a single vessel or can comprise two or more separate vessels. The reaction zone and separation zone used herein can be in the same vessel or in different vessels. For example, reactive separation techniques such as reactive distillation, reactive membrane separation, etc. can occur in the reaction zone.

[0068] The hydroformylation process of the present invention can be carried out batchwise or continuously, with optional recycling of unconsumed starting materials. The hydroformylation reaction can be carried out in a single reaction zone or in multiple reaction zones, in series or parallel, or in an elongated tubular zone or series of such reaction zones, batchwise or continuously. Materials of construction that can be used should be substantially inert to the starting materials during the reaction, and the equipment fabrication should be able to withstand the reaction temperatures and pressures.

[0069] The hydroformylation process of the present invention may be carried out in one or more steps or stages, the exact number of reaction steps or stages being governed by the best compromise between capital costs and the high catalyst selectivity, activity, life, and ease of operation achieved, as well as the inherent reactivity of the starting materials in question and the stability of the desired reaction products to the starting materials and reaction conditions.

[0070] In embodiments, hydroformylation can be carried out in a multi-stage reactor, such as that described in U.S. Pat. No. 5,728,893. Such multi-stage reactors can be designed with internal physical barriers that create more than one theoretical reaction stage per vessel. In effect, it is like having multiple reactors in a single continuous stirred tank reactor. Multiple reaction stages in a single vessel are a cost-effective way of using the volume of the reactor. This significantly reduces the number of vessels that would be required to achieve the same result. Fewer vessels reduces the overall capital and maintenance concerns associated with separate vessels and agitators.

[0071] As noted above, it is generally preferred to carry out the hydroformylation process of the present invention in a continuous manner. In general, continuous hydroformylation processes are well known in the art and may involve (a) hydroformylating an olefinic starting material with carbon monoxide and hydrogen in a liquid homogeneous reaction mixture comprising a solvent, a metal-organophosphorus ligand complex catalyst, and free organophosphorus ligand, (b) maintaining reaction temperature and pressure conditions favorable for the hydroformylation of the olefinic starting material, (c) supplying make-up amounts of the olefinic starting material, carbon monoxide, and hydrogen to the reaction medium as these reactants are depleted, and (d) recovering the desired aldehyde hydroformylation product in any desired manner. A continuous process can be carried out in a single-pass mode, i.e., the vapor mixture contains unreacted olefinic starting material and the vaporized aldehyde product is removed from the liquid reaction mixture, from which the aldehyde product is recovered and replenished with olefinic starting material, and carbon monoxide and hydrogen are supplied to the liquid reaction medium for a subsequent single pass without recycling the unreacted olefinic starting material. Such types of recycle procedures are well known in the art and may involve liquid recycle of the metal-organophosphorus complex catalyst fluid separated from the desired aldehyde reaction product, as disclosed, for example, in U.S. Pat. No. 4,148,830, or gas recycle procedures, as disclosed, for example, in U.S. Pat. No. 4,247,486, as well as combinations of both liquid and gas recycle procedures, if desired. The most preferred hydroformylation process of this invention involves a continuous liquid catalyst recycle process. Examples of suitable liquid catalyst recycling procedures are disclosed in US Pat. Nos. 4,668,651, 4,774,361, 5,102,505, and 5,110,990.

[0072] In embodiments of the present invention, the aldehyde product mixture can be separated from other components of the crude reaction mixture from which the aldehyde mixture is produced by any suitable method. Suitable separation methods include, for example, solvent extraction, crystallization, distillation, evaporation, wiped film evaporation, falling film evaporation, phase separation, filtration, etc., or any combination thereof. It may be desirable to remove the aldehyde products from the crude reaction mixture because they are formed through the use of scavengers, as described in PCT Publication No. WO 88 / 08835. One method for separating the aldehyde mixture from other components of the crude reaction mixture is by membrane separation. Such membrane separation can be achieved as described in U.S. Patent Nos. 5,430,194 and 5,681,473.

[0073] As noted above, at the end of (or during) the process of the present invention, the desired aldehyde can be recovered from the reaction mixture used in the process. For example, the recovery techniques disclosed in U.S. Pat. Nos. 4,148,830 and 4,247,486 can be used. For example, in a continuous liquid catalyst recycle process, a portion of the liquid reaction mixture (i.e., reaction fluid) containing the aldehyde product, catalyst, etc., removed from the reaction zone can be sent to a separation zone (e.g., a vaporizer / separator), and the desired aldehyde product can be separated from the liquid reaction fluid by distillation in one or more stages under atmospheric, reduced, or elevated pressure, condensed, collected in a product receiver, and, if desired, further purified. The remaining non-volatile catalyst-containing liquid reaction mixture (usually referred to as "vaporizer tails" when a vaporizer is used) can then be recycled back to the reactor, along with any hydrogen and carbon monoxide dissolved in the liquid reaction, after separating them from the condensed aldehyde product, for example, by distillation in any conventional manner, as well as any other volatile materials, such as unreacted olefins, if desired. Generally, it is preferred to separate the desired aldehyde from the catalyst-containing reaction mixture under reduced pressure and at low temperature to avoid possible decomposition of the organophosphorus ligand and reaction products.

[0074] More specifically, the distillation and separation of the desired aldehyde product from the metal-organophosphorus complex catalyst-containing reaction stream can occur at any suitable desired temperature. Generally, it is preferred that such distillation be carried out at relatively low temperatures, e.g., below 150°C, more preferably in the range of 50°C to 140°C. It is also generally preferred that such aldehyde distillation be carried out under reduced pressure, e.g., at a total gas pressure substantially lower than the total gas pressure used during hydroformylation when low-boiling aldehydes (e.g., C4-C6) are involved, or under vacuum when high-boiling aldehydes (e.g., C7 or higher) are involved. For example, a common practice is to subject the liquid reaction product medium removed from the hydroformylation reactor to reduced pressure to vaporize a substantial portion of the unreacted gas dissolved in the liquid medium containing a much lower synthesis gas concentration than that present in the reaction medium to a distillation zone, e.g., a vaporizer / separator, in which the desired aldehyde product is distilled. Generally, distillation pressures ranging from vacuum up to a maximum of 340 kPa total gas pressure are sufficient for most purposes.

[0075] As the molecular weight of the aldehyde increases, removal of the aldehyde condensation by-products ("heavies") has proven more difficult, especially in distillation processes. The high temperatures required to vaporize these high molecular weight materials tend to produce even more heavies, reaching practical limits as these heavies build up to unacceptable levels. This process generally limits catalyst life unless a catalyst purge is used as a secondary means to remove these heavies.

[0076] The present invention focuses on the recovery of rhodium from streams within a hydroformylation process. Some embodiments of the present invention are particularly useful for recovering rhodium from concentrated catalyst streams following a product (aldehyde) / catalyst separation zone. For example, if a vaporizer is used to separate the aldehyde product, some embodiments of the present invention can be used to recover rhodium from the vaporizer tail, a catalyst-containing liquid purge stream. As noted above, the catalyst in such a liquid purge stream contains a noble metal and an organophosphorus ligand.

[0077] According to embodiments of the present invention, the catalyst-containing liquid purge stream is treated with an oxidizing agent to convert organophosphorus (e.g., phosphorus(III) species) ligands to phosphorus(V) species and the corresponding oxides, which are very poor ligands for the noble metal. For purposes of the following discussion, the noble metal is considered to be rhodium, but it should be understood that the noble metal used in the catalyst can also be other noble metals disclosed herein. In the presence of a halide-free C1-C6 organic acid or a halide-free phosphoric acid, liberated rhodium is believed to be captured (complexed) by a carboxylate or phosphorous acid to form a water-soluble rhodium complex. To maximize rhodium partitioning into the aqueous phase, the amount of high molecular weight acids, such as C7-derived acids and higher aldehyde products, must be minimized. This can only be achieved by treating the purge stream with sufficient oxidizing agent under mild conditions to maximize organophosphorus oxidation while minimizing the oxidation of residual aldehydes. Additionally, it is preferable to perform this step on a concentrated catalyst purge stream in which the concentration of C7+ aldehydes has been substantially reduced (e.g., following a product-catalyst separation step).

[0078] For the purposes of this application, the phrase "halide-free" with respect to the acid used during oxidation is used to indicate the absence of halide added to the aqueous phase prior to mixing with the organic phase, while recognizing that some halide may originate from the organic phase and enter the aqueous phase. The process of the present invention, in some embodiments, substantially reduces (<0.01:1) the halide:noble metal ratio during processing so that the resulting noble metal-organophosphorus complex is substantially halide-free.

[0079] The oxidizing agent used in some embodiments of the present invention is preferably oxygen, air, oxygen diluted with an inert gas (e.g., nitrogen, argon, helium, etc.), hydrogen peroxide, alkyl peroxide, aryl peroxide, dialkyl peroxide, diaryl peroxide, or a peroxyacid having fewer than 9 carbon atoms (e.g., benzoyl peroxide).

[0080] Once the precious metal is transferred to the aqueous phase, the organic phase containing heavies and other undesirable materials (including oxidized ligands) is removed. The precious metal component of the catalyst is then reconstituted by reversing the process by contacting the aqueous phase with an organic phase under a syngas atmosphere (reducing environment), the organic phase containing the water-insoluble hydrolyzable organophosphorus ligands in the recycled olefins from the hydroformylation process. This advantageously forms a precious metal-organophosphorus complex (e.g., a new catalyst complex) in the active catalyst resting state. Because the precious metal-organophosphorus complex is insoluble in water, it migrates to the organic phase and can then be separated and returned to the hydroformylation process.

[0081] Without being bound by theory, it is believed that using low-activity olefins (e.g., recycled olefins from the hydroformylation process) dissolves the water-insoluble, hydrolyzable organophosphorus ligand under the conditions for regenerating the catalyst, and little aldehyde is produced in the process. Because aldehydes are more polar than olefins, they tend to solubilize residual halide-free acids (e.g., C1-C6 organic acids or phosphoric acid) and return them to the organic phase, which is why they are introduced into the hydroformylation process unfavorably. Furthermore, aldehydes tend to increase the density of the recovery solvent, potentially reducing the efficiency of phase separation step (d). By using a higher molecular weight, less reactive recycled olefin stream, nothing new is introduced into the hydroformylation process, and acidic carryover back to the hydroformylation process is minimized. Lower acidity reduces heavies formation and, therefore, potentially reduces the need for future purge streams.

[0082] The conditions for converting the water-soluble noble metal species back to the organic-soluble noble metal-organophosphorus complex (i.e., by contact with the water-insoluble, hydrolyzable organophosphorus ligand in the recycled olefin) are not narrowly critical. Conditions must be selected that are sufficient to convert the noble metal to a noble metal catalyst precursor or an active noble metal catalyst while minimizing the hydroformylation conversion of any olefin contained in the organic phase. In some embodiments, the step of contacting the aqueous phase with a separate organic phase (containing the water-insoluble, hydrolyzable organophosphorus ligand and the recycled olefin from the hydroformylation process) by mixing the two phases under a syngas atmosphere is carried out at a syngas pressure of 1 bar or greater. In some embodiments, such contacting is carried out at a syngas pressure of 10 bar or greater. In some embodiments, such contacting is carried out at a syngas pressure of 20 bar or greater, although it is believed that there is no advantage associated with contacting at syngas pressures greater than 20 bar. Accordingly, in some embodiments, such contacting is carried out at a syngas pressure of up to 20 bar. In some embodiments, the step of contacting the aqueous phase with a separate organic phase (comprising the water-insoluble, hydrolyzable organophosphorus ligand and recycled olefins from the hydroformylation process) by mixing the two phases under a synthesis gas atmosphere is carried out at a temperature between 0°C and 150°C. In some embodiments, such contacting is carried out at a temperature of 30°C or greater. Such contacting, in some embodiments, is carried out at a temperature of 80°C or greater. In some embodiments, such contacting is carried out at a temperature of 80°C up to 150°C. Such contacting, in some embodiments, is carried out at a temperature of 80°C up to 120°C.

[0083] The hydroformylation reaction of the olefin contained in the organic phase tends to increase the polar organic content of the organic phase, which tends to increase the solubility of any acid in the aqueous phase, which is undesirable. The concentration of the resulting aldehyde and any acid contained in the organic phase can be easily monitored by conventional analytical techniques such as gas chromatography. The use of highly hindered recycled olefins can be particularly beneficial here, in that the conversion rate to aldehydes is very slow.

[0084] Surprisingly, despite the high concentration of C1-C6 acids or phosphorous acids in the water, under the conditions required for precious metal recovery, the amount of hydrolysis of the hydrolyzable ligands is minimized. Without being bound by theory, it is believed that by minimizing the polar organic content of the organic phase, the water-insoluble hydrolyzable organophosphorus ligands are protected from acid-catalyzed hydrolysis by minimizing the amount of water and acid present in the organic phase.

[0085] In an optional embodiment, the organic phase containing the noble metal-organophosphorus complex may be washed with an aqueous wash solution containing a water-soluble amine before returning the organic phase to the hydroformylation zone. In some embodiments, the water-soluble amine has the following structure: [ka] In the formula, R 1 , R 2 , and R 3 are each independently alkyl and ethoxylate, and R 1 , R 2 , and R 3 and R is an alkyl group. 1 , R 2 , and R 3 is alkyl, the alkyl being either methyl or ethyl. 1 , R 2 , and R 3are ethoxylates. For purposes of this disclosure, "ethoxylate" refers to (-CH-CH-O) n H moiety, where n is equal to 1 or 2. A particularly desirable water-soluble organic amine for use in embodiments of the present invention is triethanolamine.

[0086] Advantageously, the water-soluble amine has two properties: 1) it is weakly basic to avoid heavy product formation in the reaction zone, and 2) it is water-soluble to avoid accumulation in the reaction fluid. The alkalinity or basicity of the water-soluble amine is generally reported as the pKa of the conjugate acid, which is advantageously between 5 and 11 at the temperature of the extraction zone. In some embodiments, the pKa is between 6.0 and 9.5, and in some particularly desirable embodiments, it is between 6.5 and 9.0. Candidate amines can be tested for heavy product formation by heating the product aldehyde with the amine at elevated temperatures. Acceptable amines will exhibit less than 1 gram of heavy product formation per liter of test solution per day at the hydroformylation temperature. The amount of heavy product formation can be readily determined by gas or liquid chromatography, as known to those skilled in the art. The minimum water solubility is at least 5% soluble in water at 25°C, and preferably miscible with water above 25°C.

[0087] The aqueous amine solution is used in an amount sufficient to produce a separate phase when heated under syngas. A mixture of amines can be used. In some embodiments, the aqueous amine solution is used in an amount to provide 2.5 to 50 weight percent of the noble metal-organophosphorus complex in the organic phase, based on the total weight of the organic phase. In some embodiments, the aqueous amine solution is used in an amount to provide 2.5 to 10 weight percent of the amine solution in such organic phase, based on the total weight of the organic phase. In some embodiments, the aqueous amine is used in an amount to provide 2.5 to 5 weight percent of the amine solution in such organic phase, based on the total weight of the organic phase. The concentration of the amine in the aqueous solution can be measured by conventional techniques well known to those skilled in the art, including, for example, gas chromatography and liquid chromatography. The amount of amine solution is not critical but should be sufficient to produce a separate phase that is decanted.

[0088] In some embodiments, an aqueous wash solution having a water-soluble amine may be present when the aqueous phase contacts a solution of a water-insoluble, hydrolyzable organophosphorus ligand dissolved at least partially in recycled olefin to form a precious metal-organophosphorus complex in the organic phase. In such embodiments, the presence of a water-soluble amine can advantageously prevent or reduce hydrolysis of the fresh hydrolyzable ligand catalyzed by residual C1-C6 organic acid or phosphorous acid.

[0089] Residual water-soluble amines as described herein may be present in the stream returned to the hydroformylation process and can optionally be removed by aqueous extractors that may already be installed to control system acidity as described in U.S. Pat. Nos. 5,741,942 and 5,741,944. Alternatively, batch or periodic aqueous washes of the organic phase with a noble metal-organophosphorus complex or a portion thereof can be carried out to remove water-soluble amines and other polar contaminants.

[0090] The amount of water-insoluble, hydrolyzable organophosphorus ligand added to form the precious metal-organophosphorus complex in the organic phase is not particularly critical, but in some embodiments should comprise at least 2 equivalents of phosphorus(III) per mole of precious metal, in some embodiments greater than 10 equivalents of phosphorus(III) per mole of precious metal, and in some embodiments greater than 15 equivalents of phosphorus(III) per mole of precious metal. There appears to be no particular advantage to adding more than 20 moles of hydrolyzable organophosphorus ligand per mole of precious metal, and the total amount added is generally limited by the solubility of the ligand in the solvent and the amount of ligand charged to the hydroformylation zone.

[0091] Exemplary non-optically active aldehyde products that can be made in a hydroformylation process to which an organic phase containing a noble metal-organophosphorus complex from the process of the present invention is added include, for example, heptanal, octanal, nonanal, 2-methyl-1-octanal, 2-ethyl-1-heptanal, 3-propyl-1-hexanal, decanal, adipaldehyde, 2-methylglutaraldehyde, 2-methyladipaldehyde, 3-methyladipaldehyde, 2-methyl-1-nonanal, undecanal, 2-methyl-1-decanal, dodecanal, and the like. 2-methyl-1-undecanal, tridecanal, 2-methyl-1-tridecanal, 2-ethyl-1-dodecanal, 3-propyl-1-undecanal, pentadecanal, 2-methyl-1-tetradecanal, hexadecanal, 2-methyl-1-pentadecanal, heptadecanal, 2-methyl-1-hexadecanal, octadecanal, 2-methyl-1-heptadecanal, nonodecanal, 2-methyl-1-octadecanal, 2-ethyl-1-heptadecanal, 3-propyl-1-hexadecanal, and the like.

[0092] Some embodiments of the present invention are described in more detail in the following examples. [Example]

[0093] All parts and percentages in the following examples are by weight unless otherwise indicated. Pressures are given as gauge pressures unless otherwise indicated. Rhodium concentration is determined by atomic absorption (AA) using an air / acetylene flame. This technique has been found not to reliably quantify clustered rhodium, and therefore this method can be used to indicate "rhodium loss" (e.g., undetectable rhodium is clustered or otherwise no longer in solution). A color change (starting from a colorless or pale yellow solution), such as blackening or the formation of a black film, or solids, also indicates decomposition of the rhodium catalyst.

[0094] Ligand A is a commercially available organic monophosphite, tris(2,4-di-tert-butylphenyl)phosphite: [ka]

[0095] Catalyst A is a hydroformylation catalyst solution having the following composition: [Table 1]

[0096] General Procedure for the Hydroformylation Process The catalyst-containing solution referenced in the following inventive examples is prepared in an N2-padded purge box and transferred via vacuum to a 100 mL Parr mini-reactor. The catalyst-containing solution is then preheated in the presence of C8 olefins and 1:1 syngas (equal parts carbon monoxide:hydrogen) at the desired reactor temperature for 30 minutes with stirring (500 rpm). During this time, a 1:1 gas pressure of approximately 50 psig is established with a Brooks Model 5866 flow meter, and after a 30-minute catalyst activation period, the reactor pressure is increased to the desired reactor pressure. The pressure is held constant for the desired run time, and total gas uptake is measured with a Brooks 0151E totalizer.

[0097] General procedure for rhodium oxide extraction experiments: Catalyst A is weighed into a 60 mL glass bottle, a stir bar is added, and the aqueous extractant solution is added, followed by the additives. The resulting biphasic solution is stirred in an oil bath at the desired temperature and continuously sparged with plant air at atmospheric pressure. After the reaction is complete, the catalyst solution bottle is removed from the oil bath, the phases are allowed to separate for 5 minutes, and samples (typically 0.2 g) are taken from each phase and analyzed by AA.

[0098] Comparative Example 1 Catalyst A (20 g) is sparged with air at 70°C for 4 hours with magnetic stirring. After the air oxidation treatment, the catalyst solution is treated with deionized water (20 g) and the biphasic solution is stirred at room temperature for 1 hour. The phases are separated and sampled for AA analysis.

[0099] Comparative Example 2 Catalyst A (20 g) is treated with deionized water (20 g) and sparged with air while magnetically stirring for 4 hours at 70° C. After the air oxidation treatment, the phases are separated and sampled for AA analysis.

[0100] Comparative Example 3 To the biphasic catalyst solution from Comparative Example 2, 4.0 g of glacial acetic acid is added and the biphasic solution is stirred at room temperature for 2 hours. The phases are separated and sampled for AA analysis.

[0101] Example 1 of the present invention The biphasic acetic acid-containing catalyst solution from Comparative Example 3 is sparged with air at 70°C while being magnetically stirred for 4 hours. During this time, the aqueous phase turns a clear gold color. After the oxidation treatment, the phases are separated and sampled for AA analysis.

[0102] Comparative Example 4: The biphasic catalyst solution from Inventive Example 1 is heated and magnetically stirred overnight at 70° C. without air sparging. The phases are separated and sampled for AA analysis.

[0103] The results of Comparative Examples 1-4 and Inventive Example 1 are summarized in Table 1. As used herein, particularly in tables, Comparative Examples may be abbreviated as "CE" and Inventive Examples may be abbreviated as "IE." [Table 2]

[0104] Comparative Examples 1-4 and Inventive Example 1 demonstrate that the transfer of the precious metal from the organic phase to the aqueous phase is successful only when air (the oxidant), water, and acetic acid (the C2 acid) are all present. However, Comparative Example 4 demonstrates that continued heating in the absence of an oxidant results in the loss of rhodium from both phases.

[0105] Example 2 of the present invention Catalyst A (20 g) is treated with 20% aqueous acetic acid (20 g) and sparged with air for 12 hours at 65° C. with magnetic stirring. After the oxidation treatment, the phases are separated and sampled for AA analysis.

[0106] Example 3 of the present invention Catalyst A (5 g) is treated with 20% aqueous acetic acid (20 g) and sparged with air for 4 hours at 65° C. with magnetic stirring. After the oxidation treatment, the phases are separated and sampled for AA analysis.

[0107] Inventive Example 4a Catalyst A (20 g) is treated with 20% aqueous acetic acid (20 g) and sparged with air for 4 hours at 65° C. with magnetic stirring. After the oxidation treatment, the phases are separated and sampled for AA analysis.

[0108] Inventive Example 4b The aqueous phase is removed from the biphasic solution resulting from Inventive Example 4a. The organic phase is recycled and treated with 20% aqueous acetic acid (20 g). The biphasic solution is sparged with air at 65°C for 4 hours while being magnetically stirred. After oxidation, the phases are separated and sampled for AA analysis.

[0109] The results of Examples 2 to 4 of the present invention are summarized in Table 2. [Table 3]

[0110] Comparative Example 4 (from Table 1) and Inventive Example 2 demonstrate that the oxidizing treatment should be performed only for the time necessary to remove rhodium from the organic phase, and that the continued presence of the oxidizing agent until the next step in the process can help avoid loss of precious metal to the insoluble metal. Inventive Examples 2-4 demonstrate that prolonged treatment has minimal effect. Inventive Example 4b demonstrates that a second extraction (rather than a single prolonged treatment) is the preferred means for obtaining maximum precious metal recovery.

[0111] Inventive Example 5a Catalyst A (10 g) is treated with 50% aqueous acetic acid (10 g) and sparged with air for 4 hours at 65° C. with magnetic stirring. After the oxidation treatment, the phases are separated and sampled for AA analysis.

[0112] Inventive Example 5b The biphasic catalyst solution from Inventive Example 5a is magnetically stirred and sparged with air for an additional 4 hours at 65° C. After oxidation, the phases are separated and sampled for AA analysis.

[0113] Inventive Example 5c The aqueous phase is removed from the biphasic solution resulting from Inventive Example 5b. The organic phase is recycled and treated with 33% aqueous acetic acid (3.8 g). The biphasic solution is sparged with air at 65°C for 4 hours while being magnetically stirred. After oxidation, the phases are separated and sampled for AA analysis.

[0114] Example 6 of the present invention Catalyst A (10 g) is treated with 70% aqueous acetic acid (10 g) and sparged with air for 4 hours at 65° C. with magnetic stirring. After the oxidation treatment, the phases are separated and sampled for AA analysis.

[0115] The results of Inventive Examples 5-6 are summarized in Table 3. Similar results to those obtained in the previous examples were seen in Inventive Examples 5-6, where more concentrated acid was used. A comparison of Inventive Examples 4a and 5a shows that higher acid content leads to improved extraction of precious metals into the aqueous phase. [Table 4]

[0116] It should be noted that the sparging process tends to remove organic matter and / or water in equipment of this scale. Therefore, although the total metal mass balance may appear to be greater than 100%, the relative distribution of metals between the phases is clearly evident.

[0117] Comparative Example 5 Catalyst A (20 g) is treated with 20% aqueous nonanoic acid (20 g) and sparged with air for 4 hours at 65° C. with magnetic stirring. After the oxidation treatment, the phases are separated and sampled for AA analysis.

[0118] Comparative Example 6 Catalyst A (20 g) is treated with 1 molar aqueous ammonium acetate (20 g) and sparged with air for 4 hours at 65° C. with magnetic stirring. After the oxidation treatment, the phases are separated and sampled for AA analysis.

[0119] Example 7 of the present invention Catalyst A (20 g) is treated with 50% aqueous citric acid (20 g) and sparged with air for 4 hours at 65° C. with magnetic stirring. After the oxidation treatment, the phases are separated and sampled for AA analysis.

[0120] Example 8 of the present invention Catalyst A (20 g) is treated with 50% aqueous phosphorous acid (20 g) and sparged with air for 4 hours at 65° C. with magnetic stirring. After the oxidation treatment, the phases are separated and sampled for AA analysis.

[0121] Example 9 of the present invention Catalyst A (20 g) is treated with 50% aqueous glutaric acid (20 g) and sparged with air for 4 hours at 65° C. with magnetic stirring. After oxidation, the phases are separated and sampled for AA analysis.

[0122] Example 10 of the Invention A catalyst solution prepared from Rh(CO)2acac (0.010 g), Ligand A (0.10 g), and isononyl aldehyde (10 g) is treated with 50% aqueous propionic acid (10 g) and sparged with air at 65 °C for 4 h while magnetically stirring. After the oxidation treatment, the phases are separated and sampled for AA analysis.

[0123] The results of Comparative Examples 5-6 and Inventive Examples 7-10 are summarized in Table 4. As shown in Table 4, various components were tested. It is clear that it is not only the carboxylate moiety that is key to recovery, but also the acid form (e.g., acetate is ineffective). Higher acids such as nonanoic acid are ineffective. [Table 5]

[0124] Example 11 of the present invention Catalyst A (10 g) is treated with 50% aqueous acetic acid (10 g) and sparged with air for 24 hours at ambient temperature with magnetic stirring. After oxidation, the phases are separated and sampled for AA analysis.

[0125] Inventive Example 12a Catalyst A (10 g) is treated with 50% aqueous acetic acid (10 g) and 30% aqueous hydrogen peroxide (0.10 g) for 24 hours at ambient temperature with magnetic stirring. After the hydrogen peroxide oxidation treatment, the phases are separated and sampled for AA analysis.

[0126] Inventive Example 12b The biphasic solution from Example 12a of the present invention is treated with an additional 30% aqueous hydrogen peroxide solution (0.30 g) at ambient temperature for 96 hours with magnetic stirring. After oxidation with hydrogen peroxide, the phases are separated and sampled for AA analysis.

[0127] The results for Inventive Examples 11 and 12 are summarized in Table 5. Using hydrogen peroxide as the oxidant at relatively low temperatures gave moderate results, but were superior to comparable air oxidation over the same time period. [Table 6]

[0128] The following example explores the extraction of rhodium from an aqueous phase into an organic recovery solvent.

[0129] Example 13 of the Present Invention Into a 60 mL glass bottle, 10.0 g of aqueous rhodium acetate solution (initial Rh concentration = 163 ppmw, approximately 40% acetic acid) is weighed, followed by 10.0 g of mixed C9 aldehydes (also containing 5.2% n-octane, unreacted olefins, and other minor components) containing 1.0 wt% Ligand A. The resulting biphasic solution is stirred under N2 until the ligand dissolves, and the solution is charged to a Parr reactor and heated to 100 °C with stirring (700 rpm) under 55 psig of 1:1 syngas for 3 hours. After 1 and 3 hours, the catalyst solution is collected and both phases are sampled for RhAA analysis.

[0130] The results of Inventive Example 13 are summarized in Table 6. [Table 7]

[0131] Example 14 of the Invention In a 60 mL glass bottle, 10.0 g of aqueous rhodium acetate solution (initial Rh concentration = 183 ppmw, approximately 40% acetic acid) was weighed, followed by 10.0 g of mixed butene dimer containing 1.0 wt. % Ligand A. The resulting biphasic solution was sparged with nitrogen for 5 minutes, followed by 1:1 syngas for 2 minutes at ambient temperature and pressure. The solution bottle was then capped, sealed with Parafilm, and heated to 70 °C for 4 hours. After the layers were allowed to phase separate, samples were taken from both phases at 1, 2, and 4 hours. The biphasic catalyst solution was then again sparged with 1:1 syngas (2 minutes), heated to 70 °C for 1 hour at ambient pressure, and samples were collected for RhAA analysis. Finally, the catalyst solution was heated to 70 °C for 1 hour at 55 psig 1:1 syngas in a Parr reactor with stirring (700 rpm). Samples were collected for RhAA analysis.

[0132] The results of Inventive Example 14 are summarized in Table 7 (nm = not determined). [Table 8]

[0133] This example demonstrates the conditions for recovering rhodium from the aqueous phase. Treatment with syngas at atmospheric pressure is effective with nonpolar olefins and Ligand A, but higher pressures produce better results. In the absence of Ligand A, severe rhodium loss is observed when higher pressures are used (rhodium black is observed). Butene dimer or butane dimer is used to model the less reactive internal olefins produced in 1-octene hydroformylation. Under the conditions (i.e., temperature and pressure) used in the recovery step, only a small fraction of these highly branched olefins is converted to aldehydes.

[0134] When mixed C9-aldehydes are used as solvents instead of butene dimers, phase separation is much slower, and non-polar olefins are taught to be preferred solvents over pure aldehydes.

[0135] Example 15 of the Present Invention Into a 60 mL glass bottle, 10.0 g of an aqueous rhodium acetate solution (initial Rh concentration = 183 ppmw, approximately 40% acetic acid) is weighed, followed by 10.0 g of mixed butene dimer containing 1.0 wt. % Ligand A. The resulting biphasic solution is stirred under N2 until the ligand dissolves, and the solution is charged to a Parr reactor and heated to 70 °C with stirring (700 rpm) under 55 psig of 1:1 syngas for 2 hours. After 1 and 2 hours, the catalyst solution is collected and both phases are sampled for RhAA analysis.

[0136] The results are shown in Table 8. Example 15 of the present invention shows excellent transfer from the aqueous phase to the organic phase under these conditions. [Table 9]

[0137] Example 16 of the present invention Catalyst A (20 g) is treated with 20% aqueous acetic acid (20 g), and the resulting biphasic solution is continuously sparged with air at 65°C for 4 hours with stirring. The phases are separated, and the aqueous acetic acid extract is collected and sparged with nitrogen at ambient temperature for 30 minutes. A solution of 1 wt% Ligand A dissolved in isononyl aldehyde (28 g) (also containing 5.2% n-octane, unreacted olefins, and other minor components) is added, and the biphasic mixture is charged to a Parr reactor and heated to 100°C for 1 hour with stirring (700 rpm) under 300 psig of 1:1 syngas. After treatment, the reactor is cooled to ambient temperature for 1 hour, the catalyst solution is collected, and both phases are sampled for RhAA analysis.

[0138] The results for Inventive Example 16 are shown in Table 9. Inventive Example 16 demonstrates excellent transfer from the aqueous phase to the organic recovery phase under these conditions. [Table 10]

[0139] Example 17 of the Present Invention Catalyst A (20 g) is added to a 100 mL glass bottle, followed by 20% aqueous acetic acid (20 g). The resulting biphasic solution is sparged with air while stirring at 65 °C for 4 hours and then cooled to room temperature. The phases are separated, and both layers are sampled for RhAA analysis. The aqueous layer is then collected and sparged with N2 at ambient temperature for approximately 1 hour. A solution of 1 wt% Ligand A dissolved in isononyl aldehyde (20 g) (also containing 5.2% n-octane, unreacted olefins, and other minor components) is added to the aqueous solution, and the resulting biphasic mixture is charged to a Parr reactor and heated / stirred at 100 °C under 300 psig of 1:1 H2:CO for 2 hours. The reactor is cooled to ambient temperature, the mixture is collected, and both phases are sampled for RhAA analysis. The results of the oxidation process and syngas recovery steps are summarized in Table 10. [Table 11]

[0140] Example 18 of the Present Invention The aqueous solution from Inventive Example 17 is then removed from the biphasic catalyst solution, and the organic catalyst solution is recharged into the Parr reactor along with 5.0 mL of mixed butene dimers and subjected to a hydroformylation test at 85°C and 250 psig syngas for 7 hours. As summarized in Table 11, the recovered hydroformylation catalyst exhibited approximately 80% of the activity of Catalyst A when subjected to the hydroformylation test, consistent with a recovery of approximately 80% of the dissolved rhodium. [Table 1] (Aspect) (Aspect 1) 1. A process for recovering rhodium from a catalyst purge stream from a C6 or higher olefin hydroformylation process, comprising: (a) treating a catalyst-containing liquid purge stream from said hydroformylation process, wherein the catalyst comprises a noble metal and an organophosphorus ligand, with an oxidizing agent in the presence of a separate liquid aqueous phase comprising a halide-free acid, wherein the halide-free acid is a C1-C6 organic acid or phosphoric acid, at a temperature sufficient to effect oxidation of a majority of the organophosphorus ligand contained therein; (b) recovering the aqueous phase; (c) contacting the aqueous phase with a separate organic phase by mixing the two phases under a synthesis gas atmosphere, the separate organic phase comprising a water-insoluble, hydrolyzable organophosphorus ligand and recycled olefins from a hydroformylation process; (d) separating and recycling said organic phase back into the hydroformylation process. (Aspect 2) 2. The process of embodiment 1, further comprising, following recovery of the aqueous phase in step (b), treating the remaining organic phase from step (a) with water, or with an aqueous solution comprising a halide-free C1-C6 organic acid or phosphoric acid, or with an oxidizing agent in the presence of a separate liquid aqueous phase comprising a halide-free C1-C6 organic acid or phosphoric acid; recovering a second aqueous phase; and combining the second aqueous phase with the aqueous phase of step (b) prior to step (c). (Aspect 3) The process of any one of aspects 1 and 2, further comprising washing the organic phase from step (d) with an aqueous wash solution prior to passing the organic phase to the hydroformylation process. (Aspect 4) 4. The process of embodiment 3, wherein the aqueous wash solution comprises a water-soluble amine. (Aspect 5)

[0023] Aspect 10. The process of any one of the preceding aspects, wherein the halide-free organic acid in step (a) is a halide-free C1-C2 organic acid. (Aspect 6) Aspect 12. The process of any one of the preceding aspects, wherein the recycled olefins are from a different hydroformylation process than the catalyst-containing liquid purge stream. (Aspect 7) 2. The process of any one of the preceding aspects, wherein the noble metal is rhodium and the organophosphorus ligand is a tertiary organophosphorus ligand. (Aspect 8)

[0033] Aspect 10. The process of any one of the preceding aspects, further comprising, following recovery of the aqueous phase in step (b), sparging the aqueous phase with an inert gas or synthesis gas prior to introducing the water-insoluble, hydrolyzable organophosphorus ligand in step (c). (Aspect 9)

[0023] The process of any one of the preceding aspects, wherein the oxidizing agent is oxygen, air, oxygen diluted with an inert gas, hydrogen peroxide, an alkyl peroxide, an aryl peroxide, a dialkyl peroxide, a diaryl peroxide, or a peroxyacid having fewer than 9 carbon atoms. (Aspect 10)

[0023] The process of any one of the preceding aspects, wherein the recycled olefins are C or higher and have a lower hydroformylation activity than the olefin feed used in the hydroformylation process that produced the catalyst-containing liquid purge stream. (Aspect 11)

[0023] Aspect 10. The process of any one of the preceding aspects, wherein the recycled olefins are C or higher and have a higher average branching degree than the olefin feed used in the hydroformylation process that produced the catalyst-containing liquid purge stream. (Aspect 12)

[0023] The process of any one of the preceding aspects, wherein the contacting of the aqueous phase with the separate organic phase in step (c) occurs at a temperature from 0°C to 150°C. (Aspect 13)

[0023] Aspect 12. The process of any one of the preceding aspects, wherein the contacting of the aqueous phase with the separate organic phase in step (c) occurs at a synthesis gas pressure of at least 1 bar.

Claims

1. 1. A process for recovering rhodium from a catalyst purge stream from a C6 or higher olefin hydroformylation process, comprising: (a) treating a catalyst-containing liquid purge stream from said hydroformylation process, wherein the catalyst comprises a noble metal and an organophosphorus ligand, with an oxidizing agent in the presence of a separate liquid aqueous phase comprising a halide-free acid, wherein said halide-free acid is a C1-C6 organic acid or phosphoric acid, at a temperature that results in oxidation of a majority of said organophosphorus ligand contained therein; (b) recovering the aqueous phase; (c) contacting the aqueous phase with a separate organic phase by mixing the two phases under a synthesis gas atmosphere, the separate organic phase comprising a water-insoluble, hydrolyzable organophosphorus ligand and recycled olefins from a hydroformylation process; (d) separating and returning the recycled organic phase to the hydroformylation process; (e) washing the organic phase from step (d) with an aqueous wash solution prior to passing the organic phase to the hydroformylation process; Including, a majority of the organophosphorus ligands contained therein means 50% by weight or more of the organophosphorus ligands contained in the liquid purge stream; the aqueous cleaning solution comprises a water-soluble amine; The process wherein the noble metal is rhodium and the organophosphorus ligand is a tertiary organophosphorus ligand.

2. 10. The process of claim 1, further comprising, following recovery of the aqueous phase in step (b), treating the remaining organic phase from step (a) with water, or with an aqueous solution comprising a halide-free C1-C6 organic acid or phosphoric acid, or with an oxidizing agent in the presence of a separate liquid aqueous phase comprising a halide-free C1-C6 organic acid or phosphoric acid, recovering a second aqueous phase, and combining the second aqueous phase with the aqueous phase of step (b) prior to step (c).

3. 3. The process of any one of claims 1 to 2, wherein the halide-free organic acid in step (a) is a halide-free C1-C2 organic acid.

4. The process of any one of claims 1 to 3, wherein the recycled olefins are from a different hydroformylation process than the catalyst-containing liquid purge stream.

5. 5. The process of any one of claims 1 to 4, wherein the oxidizing agent is oxygen, air, oxygen diluted with an inert gas, hydrogen peroxide, an alkyl peroxide, an aryl peroxide, a dialkyl peroxide, a diaryl peroxide, or a peroxyacid having fewer than 9 carbon atoms.

6. 6. The process of any one of claims 1 to 5, further comprising sparging the aqueous phase with an inert gas or synthesis gas following recovery of the aqueous phase in step (b) and prior to introducing the water-insoluble, hydrolyzable organophosphorus ligand in step (c).

7. 7. The process of any one of claims 1 to 6, wherein the recycled olefins are C6 or greater, have a lower hydroformylation activity than the olefin feed used in the hydroformylation process that produced the catalyst-containing liquid purge stream, and have a higher average degree of branching than the olefin feed used in the hydroformylation process that produced the catalyst-containing liquid purge stream.

8. 8. The process of any one of claims 1 to 7, wherein the contacting of the aqueous phase with the separate organic phase in step (c) is carried out at a temperature of from 0°C to 150°C and a synthesis gas pressure of at least 0.1 MPa (1 bar).

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