Hydroformylation process

Abstract

A hydroformylation process is disclosed having a reaction fluid comprising (a) at least one acidic compound selected from a phosphorus acidic compound or carboxylic acid compound, (b) a rhodium-organophosphorus ligand complex catalyst that comprises a rhodium complexed with an organophosphorous ligand, and, optionally, (c) free organophosphorus ligand. This reaction fluid is contacted with an aqueous extraction fluid to facilitate the separation of at least some of acidic compounds from the reaction fluid via an extraction zone aqueous effluent stream (extractor tails). The extractor tails are then sent to a decanter to facilitate further separation of the organic phase comprising rhodium from the water effluent, which can be sent for additional processing comprising wastewater treatment.

Description

[0001] HYDROFORMYLATION PROCESS

[0002] BACKGROUND OF THE INVENTION

[0003] The invention relates to a hydroformylation process and further to a reduction in the amount of rhodium lost during catalyst conditioning.

[0004] It is known that aldehydes can be produced by reacting an olefinically unsaturated compound with carbon monoxide and hydrogen in the presence of a rhodium-organophosphite ligand complex catalyst, and that preferred processes involve continuous hydroformylation and recycling of the catalyst solution as is disclosed, for example, in US Patents 4,148,830; 4,717,775 and 4,769,498. Such aldehydes have a wide range of known utility and are useful, for example, as intermediates for hydrogenation to aliphatic alcohols, for aldol condensation to produce plasticizers, and for oxidation to produce aliphatic acids.

[0005] Notwithstanding the benefits of such rhodium-organophosphorous ligand complex catalyzed liquid recycle hydroformylation processes, stabilization of the catalyst and organophosphorous ligand is a primary concern. Loss of catalyst or catalytic activity due to undesirable reactions of the highly expensive rhodium catalysts are detrimental to the production of the desired aldehyde. Degradation of the organophosphorous ligand employed during the hydroformylation process can lead to the formation of detrimental species, such as poisoning organophosphorous compounds, inhibitors, or acidic byproducts, that can lower the catalytic activity of the rhodium catalyst.

[0006] Organophosphites are known to hydrolyze when employed in continuous hydroformylation processes; the rate of hydrolysis generally being dependent on the stereochemical nature of the organophosphite. Typically, the bulkier the steric environment around the phosphorus atom, the slower the hydrolysis rate. For example, tertiary triorganophosphites, such as triphenylphosphite , are more susceptible to hydrolysis than diorganophosphites, such as those disclosed in US 4,737,588, and organopolyphosphites such as those disclosed in US 4,748,261 and US 4,769,498. All such hydrolysis reactions invariably produce phosphorus acidic compounds that catalyze the hydrolysis reactions. For example, the hydrolysis of a tertiary organophosphite produces a phosphonic acid diester, which is hydrolyzable to a phosphonic acid monoester, which in turn is hydrolyzable to H3PO3 (phosphorous acid). Moreover, hydrolysis of the ancillary products of side reactions, such as between a phosphonic acid diester and the aldehyde or between certain organophosphite ligands and an aldehyde, can lead to production of undesirable strong aldehyde acids, e.g., n-C3H7CH(OH)P(O)(OH)2. Even highly desirable stencally hindered organobisphosphites that are not very hydrolyzable can react with the aldehyde product to form poisoning organophosphites, e.g., organomonophosphites, which are catalyst inhibitors, and which are far more susceptible to hydrolysis and the formation of such aldehyde acid by-products, e.g., hydroxy alkyl phosphonic acids, as shown, for example, in US 5,288,918 and US 5,364,950. Further, the hydrolysis of organophosphite ligands may be autocatalytic in view of the production of such phosphorus acidic compounds, e.g., H3PO3, aldehyde acids, such as hydroxy alkyl phosphonic acids and the like, and if left unchecked the catalyst system of a continuous liquid recycle hydroformylation process will become more and more acidic over time. The eventual build-up of an unacceptable amount of phosphorus acidic materials can cause destruction of the organophosphite present, thereby rendering the hydroformylation catalyst totally ineffective (deactivated) and the valuable rhodium metal susceptible to loss, e.g., due to precipitation and / or deposition on the walls of the reactor.

[0007] A preferred means to mitigate hydrolysis in organophosphite-promoted hydroformylation processes is a continuous or semi-continuous biphasic extraction step, wherein a portion of the catalyst fluid is contacted with an aqueous solution comprising a buffer or neutralizing agent in an extraction zone. For example, in US 5,741,944, a buffered extractor can be used to remove acidic species as they are formed. A further enhancement is taught in US 8,884,072, wherein a water-washing step is added to remove metal salts derived from the oxyacid salt buffer prior to recycling the catalyst solution to the reaction zone. In US 1,0131,608 a water-soluble amine is added in conjunction with an aqueous extraction to neutralize acids and remove the resulting salts.

[0008] Following such a biphasic extraction, a phase separation must occur to allow the treated catalyst solution to be returned to the reaction zone. While the phases generally separate quickly within the extraction zone, surprisingly, microdroplets of catalyst solution containing rhodium may occasionally be entrained with the aqueous effluent due to variability in extractor operation or in catalyst fluid composition. For example, neutral ligand degradation products, aldehyde oligomers, etc. may accumulate in the catalyst fluid over time. If such compounds have even a slight surfactant character, they may change the rate at which the organic and aqueous phases separate; this may result in a hazy or milky aqueous effluent leaving the extraction zone.

[0009] US 5,744,649 and US 5,763,677 teach distilling the initial aqueous extraction effluent such as in a “steam stripper” to recover dissolved aldehyde. This potentially recovers valuable product and reduces the chemical oxygen demand (COD) on the wastewater treatment facility but would not recover rhodium contained in microdroplets of catalyst solution.

[0010] It would be desirable to have a means to slow the loss of rhodium from a continuous hydroformylation process comprising organophosphites which employs a biphasic extraction step to treat the catalyst.

[0011] SUMMARY OF THE INVENTION

[0012] The current invention is an improvement to biphasic extraction processes where the improvement involves sending an extraction zone aqueous effluent to a decanter to allow the aqueous effluent to separate into an organic phase and an aqueous phase, and then returning the organic phase from the decanter, preferably to the extraction zone.

[0013] More specifically, the present invention can be considered as a process comprising: (1) conducting a hydroformylation reaction in a reaction zone, wherein such hydroformylation reaction employs a reaction fluid comprising (a) at least one acidic compound selected from a phosphorus acidic compound or carboxylic acid compound, (b) a rhodium-organophosphorus ligand complex catalyst that comprises rhodium complexed with an organophosphorous ligand, and, optionally, (c) free organophosphorus ligand; (2) contacting in an extraction zone at least a portion of the hydroformylation reaction fluid with an aqueous extraction solution comprising an acid-neutralizing agent to remove at least a portion of the acidic impurities from the reaction fluid; (3) at least partially separating the aqueous extraction solution and the treated hydroformylation reaction fluid; and (4) returning the treated hydroformylation reaction fluid to the reaction zone; and (5) sending the extraction zone aqueous effluent to a decanter; (6) allowing the extraction zone aqueous effluent to at least partially separate into an organic phase and a aqueous phase; and (7) returning the organic phase from the decanter, preferably to the extraction zone.

[0014] Surprisingly it has been discovered that employing a decanter can slow the loss of rhodium from a hydroformylation process comprising organophosphites by allowing catalyst-containing microdroplets present in the aqueous effluent from an extraction zone to coalesce more quickly and form a discrete phase.

[0015] BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic drawing of one possible embodiment of the decanter.

[0017] Figure 2 is a schematic design of an alternate embodiment of the decanter.

[0018] Figure 3 is a schematic design of an alternate embodiment of the decanter.

[0019] Figure 4 is a schematic design of an alternate embodiment of the decanter. Figure 5 is a schematic design of an alternate embodiment of the decanter.

[0020] Figure 6 is a schematic design of a preferred embodiment of a hydroformylation process including a decanter as per the present invention.

[0021] DETAILED DESCRIPTION OF THE INVENTION

[0022] The disclosed process comprises (1) contacting a hydroformylation reaction fluid comprising at least one acidic compound and a rhodium-organophosphorus ligand complex catalyst with an aqueous extraction solution comprising a buffer or acid-neutralization agent in an extraction zone to form a biphasic mixture, and (2) sending the aqueous extraction solution to a decanter to promote further separation of organics comprising a rhodiumorganophosphorus ligand complex catalyst. The recovered organics are recycled back to the extraction zone and the water effluent from the decanter is sent to a wastewater treatment plant.

[0023] 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 Ed. (1991-1992) CRC Press, at page 1-10.

[0024] Unless stated to the contrary, or implicit from the context, all parts and percentages are based on weight and all test methods are current 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 its equivalent US version is so incorporated by reference) especially with respect to the disclosure of definitions (to the extent not inconsistent with any definitions specifically provided in this disclosure) and general knowledge in the art.

[0025] As used herein, "a," "an," "the," "at least one," and "one or more" are used interchangeably. The terms "comprises," “includes,” and variations thereof do not have a limiting meaning where these terms appear in the description and claims. Thus, for example, a fluid composition that includes "a" ligand degradation product can be interpreted to mean that the composition includes "one or more" ligand degradation products.

[0026] Also herein, the recitations of numerical ranges by endpoints include all numbers subsumed in that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.). For the purposes of the invention, it is to be understood, consistent with what one of ordinary skill in the art would understand, that a numerical range is intended to include and support all possible subranges that are included in that range. For example, the range from 1 to 100 is intended to convey from 1.01 to 100, from 1 to 99.99, from 1.01 to 99.99, from 40 to 60, from 1 to 55, etc. Also herein, the recitations of numerical ranges and / or numerical values, including such recitations in the claims, can be read to include the term "about." In such instances the term "about" refers to numerical ranges and / or numerical values that are substantially the same as those recited herein.

[0027] As used herein, the term “ppmw” means part per million by weight.

[0028] For purposes of this invention, the term "hydrocarbon" is contemplated to include all permissible compounds having at least one hydrogen and one carbon atom. Such permissible compounds may also have one or more heteroatoms. In a broad aspect, the permissible hydrocarbons include acyclic (with or without heteroatoms) and cyclic, branched and unbranched, carbocyclic and heterocyclic, aromatic and nonaromatic organic compounds that can be substituted or unsubstituted.

[0029] As used herein, the term "substituted" is contemplated 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, in which the number of carbons can range from 1 to 20 or more, preferably from 1 to 12, 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.

[0030] As used herein, the term "hydroformylation" is contemplated to include, but is not limited to, all hydroformylation processes that involve converting one or more substituted or unsubstituted olefinic compounds or a reaction mixture comprising one or more substituted or unsubstituted olefinic compounds to one or more substituted or unsubstituted aldehydes or a reaction mixture comprising one or more substituted or unsubstituted aldehydes. The aldehydes may be asymmetric or non- asymmetric.

[0031] For the purposes of the invention, the term “reaction zone” means one or more vessels where hydroformylation is performed. In some embodiments the reaction zone comprises vessels in series. In preferred embodiments the reaction zone comprises one or more continuous stirred tank reactors (CSTRs).

[0032] The terms "hydroformylation reaction fluid”, "reaction fluid", “reaction medium” and “catalyst solution” are used interchangeably herein, and may include, but are not limited to, a mixture comprising: (a) a metal-organophosphorous ligand complex catalyst, (b) free organophosphorous ligand, (c) aldehyde product formed in the reaction, (d) unreacted reactants, (e) a solvent tor said metal-organophosphorous ligand complex catalyst and said free organophosphorous ligand, (f) ligand decomposition products and, optionally, (g) one or more phosphorus acidic compounds and their salts formed in the reaction (which may be homogeneous or heterogeneous, and these compounds include those adhered to process equipment surfaces). The term “reaction fluid” can encompass, but is not limited to, (a) a fluid in a reaction zone, (b) a fluid stream on its way to a separation zone, (c) a fluid in a separation zone, (d) a recycle stream, (e) a fluid withdrawn from a reaction zone or separation zone, (f) a withdrawn fluid being treated with an aqueous solution, (g) a treated fluid returned to a reaction zone or separation zone, and (h) a fluid in an external cooler.

[0033] For the purposes of the invention, the terms “product / catalyst separation zone” and “vaporizer” are used interchangeably and comprise a heated zone operated at reduced pressure or in some embodiments a heated zone with flowing gases that help carry the aldehyde product vapor to a condenser.

[0034] For the purposes of the invention, the term “heavies” means compounds that have a boiling point higher than that of the desired aldehyde product(s).

[0035] For the purposes of the invention, the terms “residual catalyst solution” and “vaporizer tails” are used interchangeably and mean the non-volatile effluent from the separation zone comprising the rhodium catalyst, aldehyde product and heavies.

[0036] As used herein, the terms “extractor” and “extraction zone” are used interchangeably and mean any vessel or vessels suitable for use as a liquid / liquid extractor, that provides a suitable means for thorough contact (e.g., mixing) between the reaction fluid and an aqueous solution. This can encompass a counter-current extraction process, or a mixer settler.

[0037] For purposes of the invention, a “buffer” comprises an aqueous solution consisting of a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid. Buffers are typically metal salts of acids such as described in US 5,741,944 and US9, 174,907 B2.

[0038] For purposes of the invention, an “acid-neutralizing agent” means a base that is added to the process and reacts with acidic compounds to form salts. Weak amines such as described in US 10,131,608 whose teachings are incorporated herein by reference are examples of acid-neutralizing agents. In some embodiments the acid-neutralizing agent comprises at least one of triethanolamine, methyldiethanolamine, ethyldiethanolamine, tri(2-hydroxypropyl)amine, or ethoxylates of any of these. The terms “aqueous extraction fluid and “aqueous extraction solution are used interchangeably and refer to the liquid phase fed to and or residing within an extraction zone comprising water and a neutralization agent or buffer.

[0039] The terms “extraction zone aqueous effluent stream”, and “extractor tails” are used interchangeably and refer to an effluent stream comprising water and acid salts removed from the extraction zone following contact with the catalyst solution.

[0040] The terms “treated reaction fluid”, and “treated catalyst solution” are used interchangeably and refer to hydroformylation reaction fluid which has been contacted with aqueous extraction solution in the extraction zone.

[0041] For the purposes of the invention, the terms “decanter” and “post-extraction settler” are used interchangeably and are contemplated to include but are not limited to equipment comprising tanks, tubes, columns, and combinations thereof which facilitate phase separation of entrained organic droplets in the extractor tails. The decanter includes the coalescing and decantation zones. In contrast to the extractor, the decanter is a quiescent environment with minimal turbulence and mixing.

[0042] For the purposes of the invention, the terms “coalescing zone” is a section of the decanter which is packed or otherwise filled with a coalescing medium.

[0043] For the purposes of the invention, the terms “decantation zone” is a section of the decanter beyond the coalescing zone wherein the treated reaction fluid and aqueous extraction solution can further disengage and separate. In some embodiments two discrete phases will form in the decantation zone. In some embodiments the fluid within the decantation zone will comprise a mixture without a well-defined interface between aqueous and organics.

[0044] The term “recovered organics” means a stream comprising aldehydes residing in or leaving the decantation zone. In some embodiments the recovered organics further comprise rhodium.

[0045] The term “decanter water effluent” means a stream comprising water residing in or leaving the decantation zone.

[0046] The term “mixed decanter effluent” means a stream comprising water and organics residing in or leaving the decantation zone. The mixed decanter effluent may be routed to either the extractor, to wastewater treatment, or divided between the extractor and a wastewater treatment plant.

[0047] “Hydrolyzable phosphorous ligands” are trivalent phosphorous ligands that contain at least one P-Z bond wherein 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. The ligands may include chelate structures and / or may contain multiple P-Z moieties such as polyphosphites, polyphosphoramidites, etc. and mixed P-Z moieties such as phosphite-phosphoramidites, flurophosphite-phosphites, and the like.

[0048] The term "complex" as used herein means a coordination compound formed by the union of one or more electronically rich molecules or atoms capable of independent existence with one or more electronically poor molecules or atoms, each of which is also capable of independent existence. For example, the organophosphorous ligands employable herein may possess one or more phosphorus donor atoms, each having one available or unshared pair of electrons that are each capable of forming a coordinate bond independently or possibly in concert (e.g., via chelation) with the metal. Carbon monoxide, which is also properly classified as a ligand, can also be present and coordinated to the metal. The ultimate composition of the complex catalyst may also contain an additional ligand, e.g., hydrogen or an anion satisfying the coordination sites or nuclear charge of the metal.

[0049] Illustrative additional ligands include, for example, halogen (Cl, Br, I), alkyl, aryl, substituted aryl, acyl, CF3, C2 F5, CN, (R / hPO and RP(O)(OH)O (wherein each R is the same or different and is a substituted or unsubstituted hydrocarbon radical, e.g., the alkyl or aryl), acetate, acetylacetonate, SO4, PF4, PFe, NO2, NO3, CH3, CH2=CHCH2, CH3CH=CHCH2, CelECN, CH3CN, NH3, pyridine, (C2Hs)3N, mono-olefins, diolefins and triolefins, tetrahydrofuran, and the like. The complex species are preferably free of any additional organic ligand or anion that might poison the catalyst or have an undue adverse effect on catalyst performance.

[0050] The number of available coordination sites on rhodium is well known in the art. The catalytic species may comprise a complex catalyst mixture of monomeric, dimeric or higher nuclearity forms, which forms preferably are characterized by at least one organophosphorus-containing molecule complexed per one molecule of rhodium. For instance, it is considered that the catalytic species of the preferred catalyst employed in the hydroformylation reaction may be complexed with carbon monoxide and hydrogen in addition to one or more organophosphorous ligand(s).

[0051] The hydroformylation process, and conditions for its operation, are well known. Conducting a hydroformylation reaction involves contacting in a reaction zone CO, H2, and at least one olefin in the presence of a hydroformylation catalyst under hydroformylation conditions sufficient to form at least one aldehyde product. Illustrative examples of hydroformylation process conditions are disclosed, for example in US 5,763,679;

[0052] 5,741,945; 5,767,321; 7,446,231; 7,906,688; and 7,863,487.

[0053] The catalyst comprises rhodium and a hydrolyzable organophosphorous ligand. Illustrative examples of hydrolyzable organophosphorous ligands include diorganophosphites as disclosed in US 4,599,206; 4,717,775; and 4,835,299, triorganophosphites as disclosed in US 3,527,809 and 5,277,532 and organopolyphosphites as disclosed in US 4,688,651; 4,769,498; 4,774,361; 4,885,401; 5,113,022; 5,179,055; 5,202,297; 5,235,113; 5,254,741; 5,264,616; 5,312,996; 5,364,950; 5,391,801.

[0054] The substituted or unsubstituted olefinic unsaturated reactants that may be employed in the hydroformylation process include both optically active (prochiral and chiral) and non-optically active (achiral) olefinic unsaturated compounds containing from 2 to 40, preferably 3 to 20, carbon atoms. These compounds are described in detail in US 9,695,098. . Such olefinic unsaturated compounds can be terminally or internally unsaturated and be of straight-chain, branched chain or cyclic structures, as well as olefin mixtures, such as obtained from the oligomerization of propene, butene, isobutene, etc. (such as so called dimeric, trimeric or tetrameric propylene and the like, as disclosed, for example, in US 4,518,809 and 4,528,403).

[0055] In one aspect the process of the invention comprising preventing and / or lessening hydrolytic degradation of the organophosphite ligand and deactivation of the metal-organophosphite ligand complex catalyst by contacting at least a portion of the hydroformylation reaction fluid with an aqueous extraction solution comprising one or more acid-neutralizing agents or buffers is essentially a “non-aqueous” process. The primary solvent for the hydroformylation catalyst is an organic solvent such as described above and a separate water phase in the reaction zone is to be avoided. Some water will be dissolved in the organic fluid due to the solubility of water in the organic phase in the extractor but typically represents less than 5wt% of the liquid phase in the reaction zone, preferably less than 2wt%.

[0056] Illustrative rhodium-organophosphorous ligand complex catalyzed hydroformylation processes that may experience hydrolytic degradation include those processes as described, for example, in US Patents 4,148,830; 4,593,127; 4,769,498; 4,717,775; 4,774,361;

[0057] 4,885,401; 5,264,616; 5,288,918; 5,360,938; 5,364,950; 5,491,266 and 7,196,230. Species containing the P-Z moiety that will likely undergo hydrolytic degradation include organophosphonites, phosphoramidites, and fluorophosphonites such as described WO 2008 / 071508, WO 2005 / 042458, and US Patents 5,710,344, 6,265,620, 6,440,891, 7,009,068, 7,145,042, 7,586,010, 7,674,937, and 7,872,156.

[0058] Mixtures of catalysts can be employed. The amount of rhodium-organophosphorous ligand complex catalyst present in the reaction fluid need only be that minimum amount necessary to provide the given rhodium concentration desired to be employed and that will furnish the amount necessary to catalyze the particular hydroformylation process involved such as disclosed, for example, in the above-mentioned patents. In general, rhodium concentrations in the range of from 10 ppmw to 1000 ppmw, calculated as free metal in the reaction medium, should be sufficient for most processes, while it is generally preferred to employ from 10 to 500 ppmw of metal, and more preferably from 25 to 350 ppmw of rhodium.

[0059] Rhodium concentration may be measured by analytical methods which are known to the skilled person. Suitable analytical methods include but are not limited to inductively coupled plasma mass spectroscopy, atomic absorption spectrosocopy (AA), and X-ray fluorescence (XRF).

[0060] In addition to the rhodium-organophosphorous ligand complex catalyst, free organophosphorous ligand (i.e., ligand that is not complexed with the metal) may also be present in the reaction medium. The free organophosphorous ligand may correspond to any of the organophosphorous ligands discussed above. It is preferred that the free organophosphorous ligand be the same ligand employed in the rhodium-organophosphorous ligand complex. However, such ligands need not be the same in any given process. The hydroformylation process of this invention may involve from 0.1 moles or less to 100 moles or higher of free organophosphorous ligand per mole of rhodium in the reaction medium. Preferably, the hydroformylation process is carried out in the presence of from 1 to 50 moles of organophosphorous ligand per mole of rhodium present in the reaction medium. More preferably, for organopolyphosphites, from 1.1 to 4 moles of organopolyphosphite ligand are employed per mole of rhodium. Said amounts of organophosphorous ligand are the sum of both the amount of organophosphorous ligand that is bound (complexed) to the rhodium present and the amount of free organophosphorous ligand present. If desired, additional organophosphorous ligand can be supplied to the reaction medium of the hydroformylation process at any time and in any suitable manner, e.g., to maintain a predetermined level of free ligand in the reaction medium.

[0061] Ligand concentrations can be measured by analytical methods known to the skilled person. Suitable analytical methods include but are not limited to phosphorous-31 nuclear magnetic resonance spectroscopy (31P NMR) and high-performance liquid chromatography (HPLC).

[0062] The reaction zone comprises one or more suitable reactors such as a continuous stirred tank reactor (CSTR). The optimum size and shape of a reactor will depend on the type of reactor used. The reaction zone may be a single vessel or may comprise two or more discrete vessels in series or in parallel. The reaction steps may be affected by the incremental addition of one of the starting materials to the other. Also, the reaction steps can be combined by the joint addition of the starting materials. When complete conversion is not desired or not obtainable, the starting materials can be separated from the product, for example by distillation, and the starting materials then recycled back into the reaction zone.

[0063] The catalyst liquid recycle operation generally involves (1) withdrawing a portion of the liquid reaction medium containing the catalyst and aldehyde product from the reaction zone; (2) recovering the aldehyde product therefrom in a product / catalyst separation zone; (3) treating at least a portion of the residual catalyst in the extraction zone; and (4) returning the treated catalyst solution to the reaction zone.

[0064] The product / catalyst separation zone employed may be a single vessel or may comprise two or more discrete vessels. In preferred embodiments, the aldehyde product mixture is vaporized away from the other components of the crude reaction mixtures by any suitable method such as distillation, wiped film evaporation, falling film evaporation and the like or any combination thereof.

[0065] Condensation of the volatilized materials, and separation and further recovery thereof, e.g., by further distillation, can be carried out in any conventional manner.

[0066] Generally, the crude aldehyde can be passed on for further purification and isomer separation, hydrogenation, oxidation, and / or condensation, if desired, and any recovered reactants, e.g., olefinic starting material and syngas, can be recycled in any desired manner to the hydroformylation zone (reactor).

[0067] More particularly, separation of the desired aldehyde product from the metal-organophosphorous complex catalyst containing reaction fluid may take place at any suitable temperature. In general, it is preferred that the separation take place at relatively low temperatures, such as below 150°C, and more preferably at a temperature in the range of from 50°C to 140°C. It is also generally preferred that the product I catalyst separation take place under reduced pressure, e.g., a total gas pressure that is substantially lower than the total gas pressure employed during hydroformylation when low boiling aldehydes (e.g., C4 to C&) are involved or under vacuum when high boiling aldehydes (e.g., C7 or greater) are involved. For instance, a common practice is to subject the liquid reaction product medium removed from the hydroformylation reactor to a pressure reduction to volatilize a substantial portion of the unreacted gases before the fluid enters the separation zone. In general, distillation pressures ranging from vacuum pressures to total gas pressure of 340 kPa should be sufficient for most purposes. In preferred embodiments the product / catalyst separation zone comprises a vaporizer comprised of a heated zone with flowing gases that help carry the aldehyde product vapor to a condenser. Descriptions of such vaporizers may be found for example in US 4,166,773A, US 5,288,918 and US 8,404,903 which are incorporated herein by reference.

[0068] In one aspect, at least a portion of the non-volatile catalyst-containing residue (vaporizer tails) is treated via aqueous extraction. The aqueous extraction step is conducted in an extraction zone, which may be a single vessel or may comprise two or more discreet vessels. In one embodiment of the invention, a reaction vessel may be employed as an extractor, e.g., when the process is operated in batch mode. Generally speaking, the extraction zone comprises mixing of the reaction fluid and the aqueous extraction solution to promote distribution of acidic impurities and or / salts of acidic impurities to the aqueous phase. Some aspects of how the hydroformylation reaction fluid and aqueous extraction solution are contacted and the treatment conditions such as temperature, pressure and contact time are not narrowly critical and obviously need only be sufficient to obtain the desired result.

[0069] The pH in the aqueous extraction zone is a critical variable and as such must be measured and controlled. Measurement of pH can be done using any means known to those skilled in the art including, for example, by conventional titration or commercially available pH meters with proper calibration. For the purposes of the invention, it is assumed that the pH of the aqueous effluent leaving the extractor (e.g., extractor tails) is representative of the pH throughout the extraction zone.

[0070] The pH range of the extractor tails stream may range from 4.5 to 9.0, preferably from 5.6 to 8.0, more preferably from 6.0 to 7.5, and most preferably, from 6.3 to 7.2. Occasionally, relatively higher pH values between 7.0 and 9.0 may be employed for short periods to mitigate high ligand decomposition periods, such as during a process upset when high ligand hydrolysis is observed, but this will result in a slow buildup of poisoning phosphite if continued for prolonged periods. Alternatively, relatively lower pH values (about 6.0) may be used for short times for maximum reactivity and olefin conversion (due to minimum poisoning phosphite concentration) at the cost of higher ligand usage. It is recognized that the term “pH” is properly defined only for aqueous systems.

[0071] In some embodiments the aqueous extraction solution comprises water-soluble amines; in such embodiments the pH may be controlled by varying the addition rate of the water-soluble amine. Additional details of the use of water-soluble amines in the extraction zone may be found in US 10,131,608 B2 which is incorporated herein by reference.

[0072] In some embodiments the aqueous extraction solution comprises one or more buffers. The amount of buffered water flow and / or the ratio of salts (which determine the buffered water feed pH) and / or the molarity of the aqueous solution can be altered in a likewise manner to control the extractor tails pH. Additional details of the use of buffers to control the extraction zone pH may be found in US 5,741,944 and US 9,174,907 B2 which are incorporated herein by reference.

[0073] In one embodiment, mixing is accomplished by passing the hydroformylation reaction fluid through the aqueous extraction solution in a sieve tray extractor column in a counter-current fashion. In other embodiments the column may comprise reciprocatingplates, structured or unstructured packing, and the like. In one embodiment mixing is accomplished by pumping the reaction fluid through a nozzle or restricting orifice into the extraction zone containing aqueous extraction solution. In one embodiment the biphasic mixture is circulated within the extraction zone in a pump-around loop to affect mixing. The amount of aqueous extraction solution employed need only be that which is sufficient to neutralize and remove at least some of the phosphorous acidic compounds.

[0074] In one embodiment, the process of the invention employs an aqueous extraction step together with the addition of low levels of a water-soluble but relatively weak basic amine to the hydroformylation reaction fluid in the reaction zone. One function of the amine is to neutralize acidic impurities. The neutralized acids are salts, e.g., ammonium salts. It is desirable to remove these salts to prevent their accumulation, which can lead to fouling and side reactions of the salts. In a preferred embodiment the excess amine additive and neutralized acidic species leave the process in the extractor tails.

[0075] The amine advantageously may perform at least one of the following two functions: 1) neutralize acids, e.g. in the reaction zone, to mitigate ligand and catalyst degradation; and 2) control pH in the extraction step.

[0076] The extraction step advantageously may serve at least one of the following three functions: 1) removing the neutralized acidic species (either as the salt or the acid) from the system, 2) providing water to the catalyst solution for poisoning phosphite degradation, and 3) preventing amine buildup to avoid excessive heavies formation. The combination of the three features provides a self-balancing system where extremes of effective pH and heavies formation are avoided while still allowing controlled poisoning phosphite hydrolysis.

[0077] The amine may be added to the process at essentially any point so long as the desired concentration of amine is achieved. For example, the amine advantageously is added to the process in at least one of the reaction zones and / or the extraction zone. In one embodiment, the water-soluble amine is added to the process in more than one location. In one embodiment of the invention, the amine is added to the water feed to the extraction zone. In one embodiment of the invention, the amine is added to the first reactor. The water-soluble amine can be the same or different at the two addition points.

[0078] In one embodiment of the invention, the amine is primarily or entirely added to the reaction zone, and the rate of addition is varied to control the pH of the extractor tails. In another embodiment of the invention, the amine is primarily added to the extraction zone, and the rate of addition of the water-soluble amine to the extraction zone is varied to control the pH of the extractor tails. In one embodiment of the invention, the amine is introduced to the extraction zone as part of the aqueous feed stream.

[0079] In one embodiment, the water soluble, weak amine is added as a water solution rather than the pure amine. Such amines may be viscous liquids or solids thus it may be more convenient to add the amine as a dilute aqueous solution which also contributes to a more even distribution of the amine in the hydroformylation solution and easier process control. Likewise, the oxy-acid salts (such as sodium phosphates) are also preferably delivered to the extraction zone as water solutions.

[0080] In one embodiment, the acid neutralization agent advantageously is removed from the process with the water phase that exits the extraction zone. Thus, additional acid neutralization agent should be added to the process to maintain the desired concentration of the acid neutralization agent.

[0081] In a preferred embodiment of the invention, at least a portion of the water-soluble amine is removed with the aqueous layer or phase of the extraction zone and, therefore, the amine does not build up in the organic phase. Water-soluble amines will generally distribute preferentially to the aqueous phase and are thereby continuously removed preventing build up in the organic layer or phase.

[0082] In one aspect the process of the invention involves the initial liquid-liquid phase separation in the extraction zone wherein an upper phase comprising treated catalyst solution forms above a lower phase comprising aqueous extraction solution. This initial separation occurs following contacting of the catalyst solution with the aqueous extraction solution in the extraction zone.

[0083] The solubility of water in the reaction fluid is limited as is the solubility of the organic compounds comprising the reaction fluid (e.g., aldehydes, aldehyde oligomers, organophosphite ligands and the like) in the aqueous extraction solution, thus two phases will generally be present in the extraction zone. The reaction fluid is generally less dense than the aqueous extraction solution, thus the reaction fluid will tend to rise to the top of the extraction zone. For example, in an embodiment wherein the extraction zone comprises a sieve tray extractor column predominantly filled with aqueous extraction solution, reaction fluid introduced near the bottom of the column will rise as globules and travel through the trays. In such an embodiment the globules will coalesce to form an organic layer comprising treated reaction fluid near the top of the column. In some embodiments the treated reaction fluid is returned to the reaction zone without further processing. In a preferred embodiment, the treated reaction fluid is further contacted with water to reduce dissolved impurities such as taught in US 8,884,072 before being returned to the reaction zone.

[0084] In some instances, an intermediate (or rag) layer may form between the treated catalyst solution and aqueous extraction solution layers. Depending on the operation of the extraction zone (e.g., rate of vaporizer tails flow) and variations in the phase compositions the aqueous extraction solution may comprise suspended microdroplets of catalyst solution; in such cases the aqueous extraction solution may appear hazy or milky. The process of the invention lessens the likelihood that rhodium will be sent to wastewater treatment during such periods.

[0085] Following the initial phase separation in the extraction zone, the aqueous extraction solution is removed from the extraction zone as an extractor tails stream and transferred to the decanter.

[0086] In some embodiments the extractor tails stream will form a discrete organic phase in the decantation zone as microdroplets coalesce and / or dissolved aldehyde comes out of solution. In such embodiments...

[0087] The height of the interface between the two liquid phases can be measured by a level transmitter / level detector. Examples of suitable types of level transmitters include guided wave radar level transmitters, non-contacting radar level transmitters, differential pressure (DP) level transmitters, magnetic level transmitters and the like. Such devices are commercially available and are well known to the skilled person. In one embodiment the level transmitter is used in conjunction with a process control system to automate flow rate adjustments for the various streams.

[0088] In some embodiments, the interface between the two phases may not be well defined. In such embodiments conductivity measurements can be used to gauge the relative organic content at key points. As the organic content of a mixed phase comprising water and organics increases, the conductivity will generally decrease. On-line conductivity meters are commercially available and are well known to the skilled person.

[0089] In one aspect the decanter comprises a coalescing zone filled or otherwise packed with coalescing media. In some embodiments the coalescing media comprises a hydrophobic material which promotes collision of organic droplets over a high surface area. Suitable materials of construction for the coalescing media include but are not limited to PVC, CPVC, polypropylene, stainless steel and the like. In some embodiments the coalescing media comprises a spiral wound membrane element. Such coalescing media are commercially available and are well known to the skilled person. The exact nature of the coalescing media is not a critical aspect of the invention.

[0090] In one aspect the recovered organic stream is returned to the extraction zone. This strategy avoids unintentional addition of aqueous extraction solution to the reaction zone and thereby makes the process of the invention more robust and tolerant of variation in rate and degree of phase separation.

[0091] FIG. 1 illustrates an example of a decanter of the invention. With reference to FIG.

[0092] 1, the extractor tails stream 1 is fed to the decanter and moves through the coalescing zone 2. The zone 2 effluent is collected in a vertical decanting zone where in some embodiments two phases are allowed to form comprising water and recovered organics. The height of the interface between the two liquid phases is measured and maintained within the target range by a combination of (a) adjusting the removal rate of the top layer from the vertical section as a recovered organics stream 3 and recycling it, preferably back to the extraction zone, (b) adjusting the removal rate of the decanter water effluent as stream 4 from the bottom of the decanting section to further processing comprising wastewater treatment, and (c) adjusting the flow rate of stream 1.

[0093] FIG. 2 illustrates another example of a decanter of the invention. With reference to FIG. 2, the extractor tails stream 1 is fed to the decanter and the mixed fluid moves through the coalescing zone 2. The zone 2 effluent is collected in a vertical decanting section where in some embodiments two phases are allowed to form comprising water and recovered organics. As the liquid level in the decanting section increases, the upper phase begins to spill over a weir 5 after which it is recycled back to the extraction zone as a recovered organics stream 3. The height of the interface between the two liquid phases is measured and maintained within the target range by a combination of (a) adjusting the rate of flow of stream 1 into the decanter and (b) adjusting the rate at which the decanter water effluent is removed from the bottom of the decanting section as stream 4 to further processing comprising wastewater treatment.

[0094] FIG. 3 illustrates another example of a decanter of the invention. With reference to FIG. 3, the extractor tails stream 1 is fed to the decanter and the mixed effluent rises through the coalescing zone 2. The zone 2 effluent moves into a decanting section featuring a vertical plate or barrier 5, which functions as a weir and creates an area of low turbulence on its far side. The height of the interface between the two liquid phases is measured and maintained within the target range by a combination of (a) adjusting the rate of removal of the top layer as a recovered organics stream 3 and recycling it back to the extraction zone, and (b) adjusting the rate at which the lower layer is removed as a decanter water effluent stream 4 to further processing comprising wastewater treatment, and (c) adjusting the flow rate of stream 1 into the decanter.

[0095] FIG. 4 illustrates another example of a decanter of the invention. With reference to FIG. 4, the extractor tails stream 1 is fed to the decanter and the mixed effluent rises through the coalescing zone 2. The zone 2 effluent moves into a decanting section comprising a vertical plate or barrier 5, which functions as a weir and creates an area of low turbulence on its far side. The conductivity of the fluid near the top and bottom of the decanting section is measured by conductivity probes 6 and 7 respectively. In some embodiments the conductivity measurement indicates an organic rich zone at the top, in such embodiments a recovered organic stream 3 is removed from the top of the decantation zone and recycled to the extractor. When the conductivity measurement indicates an organic lean zone at the top of the decanting section, the flow rate of stream 3 is reduced or stopped. In such embodiments the flow rates of the streams are balanced such that the combined flow rates of 3 and 4 are approximately equal to 1. In some embodiments the combined flow rates of 3, 4 and 1 are adjusted to maximize the conductivity delta between 6 and 7 (i.e., minimal conductivity at 6 and maximum at 7).

[0096] FIG. 5 illustrates another example of a decanter of the invention. With reference to FIG. 5, the extractor tails stream 1 is fed to the decanter and the mixed effluent passes through the coalescing zone 2. The zone 2 effluent moves into the decanting section comprising a tall narrow section at the top (e.g., pipe or standpipe) which promotes formation of a discrete upper layer in instances when the concentration of recovered organics is low. The conductivity of the fluid near the top, middle and bottom of the decanting section is measured by conductivity probes 6. The conductivity measurements can be used to appropriately balance the flow rates of streams 3 and 4 such that they are approximately equal to the flow rate of 1.

[0097] FIG. 6 is a schematic of a hydroformylation process comprising a decanter of the invention. With reference to Fig 6, the fluid from the reaction zone 8 is sent via stream 9 to the vaporizer 10. The vaporizer tails stream 11 enters the extraction zone 12. The organic phase from the extractor is returned to the reaction zone via stream 13. The extractor tails stream comprising water (14) is sent to the decanter 15. The organic phase from the decanter (16) is returned to the extraction zone while the aqueous phase from the decanter is sent for wastewater treatment via stream 17.

[0098] Conductivity probes can be strategically located within any of the decanter designs (see for example in FIG 4). Measuring conductivity can provide an alternative control strategy during periods of operation when a discrete organic phase doesn’t readily form or is difficult to measure (e.g., when the organic content of the extractor tails stream is exceptionally low).

[0099] In embodiments where the catalyst separation zone comprises a vaporizer, the temperature of the extraction zone is generally > 40 ° C due to the elevated temperature of the incoming vaporizer tails. Thus, the extractor tails will enter the decanter saturated with aldehyde product at about 400C. It has surprisingly been discovered that the solubility of butyraldehyde in the extractor tails increases as the temperature declines. In one aspect, the decanter is insulated to slow heat loss from the coalescing and decantation sections thereby slowing the redissolving of aldehyde. Preferably the decanter is at a temperature greater than 20°C, 30°C, or even 40°C.

[0100] In one embodiment the decanter is heated to minimize the solubility of butyraldehyde in the water effluent from the decantation zone. Heating may be supplied in any manner, such as for example steam, hot oil, electric heaters, etc.

[0101] The concentration of organics comprised of aldehyde product in the aqueous solutions and streams may be measured by gas chromatography (GC). Such methods and techniques are well known to the skilled person. Conductivity may also be used to gauge if the fluid at various point is rich in organics.

[0102] SPECIFIC EMBODIMENTS OF THE INVENTION All parts and percentages in the following examples are by weight unless otherwise indicated. Pressures are given as absolute pressure unless otherwise indicated. Rhodium is measured by atomic absorption (AA). The level of detection is determined to be 0. 2 ppmw, thus samples in which rhodium is not detected are considered to contain < 0.2 ppmw.

[0103] Comparative Experiment 1 :

[0104] An industrial process utilizing a rhodium-bisphosphite catalyst for the continuous hydroformylation of propylene employs a counter-current sieve tray extractor column to remove acidic ligand degradation products from the vaporizer tails (rhodium concentration about 220 ppmw). The aqueous extraction solution is comprised of sodium phosphate buffer with a pH of about 7.8. The Extractor Tails are sampled periodically over an 8-month period and allowed to stand at room temperature until the aqueous layer is substantially clear. In each case a small, discrete organic phase is observed after standing; the amount of organic phase varies widely. Select samples are analyzed by AA for rhodium; the results are summarized in Table. 1, with “BDL” indicating that the amount was below the detectable limit.

[0105] Table 1.

[0106]

[0107] The results of Table 1 show that the Extractor Tails sometimes contain microdroplets of catalyst solution comprising rhodium. Additionally, it shows that not all the observed organic phases contain catalyst, which indicates that in some cases the organic phases are comprised of dissolved aldehyde that has come out of solution. The results of Table 1 also show that rhodium solubility in the aqueous extraction solution is extremely low.

[0108] Example 1:

[0109] Water (151.09 g) and n-butyraldehyde (25.09 g) are mixed thoroughly in a separatory funnel at 3 °C. The resulting mixture is allowed to separate until two clear phases are observed. Each of the phases is collected and weighed. The solubility of n-butyraldehyde in the aqueous phase is calculated based on the mass of the residual organic phase. The results are shown in Table 2.

[0110] The procedure of Example 1 is repeated at 24 °C. The results are summarized in Table 2.

[0111] Table 2.

[0112]

[0113] The results of Table 2 show that the solubility of n-butyraldehyde decreases as temperature increases.

[0114] Comparative Experiment 2:

[0115] An industrial process utilizing a rhodium-bisphosphite catalyst for the continuous hydroformylation of propylene employs a counter-current sieve tray extractor column to remove acidic ligand degradation products from the vaporizer tails (rhodium concentration about 220 ppmw). The aqueous extraction solution is comprised of triethanolamine and has a pH of about 7.9. A sample of Extractor Tails is observed to have a thin discrete organic layer, a small rag layer and an aqueous layer. The sample is shaken to create a more homogeneous mixture and then allowed to stand at room temperature without agitation. After 5 minutes a thin organic film is observed overtop of a hazy aqueous layer.

[0116] Example 3 :

[0117] The procedure of Comparative Experiment 2 is repeated except for pouring the nearly homogeneous mixture slowly through a coalescing zone comprised of a 1.2 cm pad of cellulose fibers (bulk density 0.135 g / ml) which had been wetted with Extractor Tails. The coalescing zone effluent is allowed to stand at room temperature without agitation. After 5 minutes a more substantial organic layer (relative to Comparative Experiment 2) forms overtop a clear aqueous layer. The cellulose fiber pad is then squeezed to remove trapped liquid, which is rich in organic phase relative to the Extractor Tails feed. Comparative Experiment 3 :

[0118] The procedure of Comparative Experiment 2 is repeated except for pouring the nearly homogeneous mixture slowly through a coalescing zone comprised of a pad of stainless-steel wire mesh (bulk density 0.170 g / ml) which had been wetted with Extractor Tails. The coalescing zone effluent is allowed to stand at room temperature without agitation. After 5 minutes there is no appreciable difference relative to Comparative Experiment 2.

[0119] Example 4:

[0120] The procedure of Comparative Experiment 2 is repeated except for pouring the nearly homogeneous mixture slowly through a coalescing zone comprised of a glass wool pad (bulk density 0.1 g / ml) which had been wetted with Extractor Tails. The coalescing zone effluent is allowed to stand at room temperature without agitation. After 5 minutes a clearer thin organic layer forms overtop an aqueous layer which is more clear than Comparative Experiment 2. The glass wool pad is then squeezed to remove trapped liquids, which are rich in organic phase relative to the Extractor Tails feed.

[0121] The result of Examples 3 and 4 show that the process of the invention will provide a decanter water effluent stream that is relatively free of organic droplets.

Claims

WHAT IS CLAIMED IS:

1. A process comprising: (1) conducting in a reaction zone a hydroformylation reaction employing a reaction fluid comprising (a) at least one acidic compound selected from a phosphorus acidic compound or carboxylic acid compound, (b) a rhodiumorganophosphorus ligand complex catalyst that comprises rhodium complexed with an organophosphorous ligand, and, optionally, (c) free organophosphorus ligand; (2) contacting at least a portion of the hydroformylation reaction fluid with an aqueous extraction solution comprising an acid-neutralizing agent or buffer to remove at least a portion of the acidic impurities; (3) at least partially separating in an extraction zone the aqueous extraction solution and the treated hydroformylation reaction fluid; and (4) returning the treated hydroformylation reaction fluid to the reaction zone; and (5) sending the extraction zone aqueous effluent to a decanter; and (6) returning the recovered organic phase from the decantation zone to an earlier stage of the process.

2. The process of claim 1 wherein the decanter comprises a coalescing zone.

3. The process of claim 1 wherein the decanter comprises a decantation zone4. The process of claim 1 wherein the decanter comprises both a coalescing zone and a decantation zone.

5. The process of claim 1 wherein the recovered organic phase from the decantation zone is returned in step (6) to the extraction zone.

6. The process of claim 1 wherein the recovered organic phase from the decantation zone is returned in step (6) to the reaction zone.

7. The process of claim 1 wherein the decanter is at a temperature greater than 20°C.

8. The process of claim 1 wherein the decanter is at a temperature greater than 30°C.

9. In a process for conducting a hydroformylation reaction in a reaction zone, where such process employs a hydroformylation reaction fluid comprising a phosphorus acidic compound or carboxylic acid compound, and a rhodium-organophosphorus ligand complex catalyst, and where the hydroformylation reaction fluid is contacted with an aqueous extraction solution comprising an acid-neutralizing agent or buffer in an extraction zone to remove at least a portion of the acidic impurities before returning the treated hydroformylation reaction fluid to the reaction zone; the improvement comprising:sending the aqueous effluent from the extraction zone to a decanter and allowing the aqueous effluent to separate into an aqueous phase and an organic phase; andreturning the recovered organic phase from the decanter to the extraction zone.

10. The process of claim 9 wherein the decanter comprises a coalescing zone and a decantation zone.

11. The process of claim 9 wherein the temperature of the decanter is greater than 20°C.

Images