Process for improving rhodium / phosphite-based homogeneous hydroformylation catalyst activity

Abstract

The present invention relates to a hydroformylation process for producing aldehydes, the hydroformylation process comprising contacting reactants comprising an olefin, hydrogen and CO in a reaction zone in the presence of a rhodium-organophosphite-based catalyst, optionally with a free organophosphite ligand, in the presence of a soluble Group VII metal complex additive, wherein the Group VII complex additive is present in a molar ratio greater than 2: 1 compared to rhodium.

Description

TECHNICAL FIELD

[0001] The present invention relates to homogeneous olefin hydroformylation processes, and in particular to hydroformylation processes utilizing a recycle stream having dissolved rhodium-phosphite complex catalyst. BACKGROUND

[0002] It is known in the art that aldehydes can be readily produced by reacting an olefinically unsaturated compound with carbon monoxide and hydrogen in the presence of a dissolved rhodium-phosphite ligand complex catalyst, and a preferred type of such process includes continuous hydroformylation and recycle of the catalyst, such as disclosed in, for example, U.S. Patent No. 4,599,206. Typically, such processes utilize liquid recycle, although batch processes or gas recycle hydroformylation processes are also feasible.

[0003] While such dissolved rhodium-phosphite complex catalyzed liquid recycle hydroformylation processes have benefits, in some instances the rhodium in some rhodium-phosphite complex catalysts can lose activity and / or precipitate from solution as rhodium metal or in the form of rhodium clusters during hydroformylation. Rhodium is very expensive, so loss of activity or separation of rhodium from solution is a serious economic problem for commercial use of these catalysts.

[0004] The use of stripping gas evaporators, including the addition of CO to mitigate rhodium loss during the evaporation stage, have been reported (see, for example, U.S. Patent 8,404,903 and PCT Publication WO2016 / 089602). However, such systems require a large capital expenditure and are not easily retrofitted to existing facilities.

[0005] The use of polymeric additives containing polar functional groups to mitigate rhodium loss has been found, as reported in U.S. Patent 4,774,361 and US 11,111,198. However, these additives only retain activity.

[0006] A large number of reports using mixed transition metal homogeneous catalyst systems claim improved catalyst performance. For example, US 4,262,141 teaches hydroformylation with a Rh / phosphorane catalyst in the presence of a copper, silver or zinc additive. US 5,756,855 A employs a Group VIII metal (other than rhodium) to stabilize a rhodium / monophosphite catalyst, and US 4,306,086 A teaches stabilization and regeneration of a rhodium / triarylphosphorane complex based hydroformylation catalyst by the addition of a cobalt compound. US 4,200,592 A teaches the addition of a homogeneous Group VI or Group VIII metal promoter increases the activity of homogeneous rhodium-based hydroformylation of internal olefins at low pressure using a rhodium / organic phosphorus catalyst. They report that Group VII metals have no effect on the performance of rhodium / triarylphosphorane based catalysts.

[0007] Alternative approaches to improving the activity of rhodium / phosphite-based homogeneous hydroformylation catalysts are desired. This would enable a reduction in rhodium cost and / or a reduction in reaction temperature, which can promote longer catalyst life and lower heavy formation. SUMMARY

[0008] Alternative approaches to increasing the activity of catalysts in a hydroformylation process utilizing a recycle stream of rhodium-phosphite complex catalyst have been advantageously discovered. Some embodiments of the invention advantageously provide a rhodium-phosphite complex catalyzed hydroformylation process of liquid recycle operation of olefins (C3and higher) with improved solubility, wherein the activity of the rhodium-phosphite catalyst is increased, thus reducing the amount of rhodium catalyst required to produce a specific aldehyde production rate. Alternatively, the higher activity can allow for lower reaction temperatures, which can promote longer catalyst life, lower ligand degradation, lower aldehyde condensation reactions (i.e., heavy formation), or other undesirable side reactions.

[0009] In one aspect, a homogeneous olefin hydroformylation process for producing aldehydes comprises: (1) contacting reactants comprising (a) an olefin, (b) hydrogen, and (c) CO in a reaction zone in the presence of: (d) a catalytic amount of a soluble rhodium-monophosphite-based catalyst, optionally with free organic phosphite ligand, wherein the monophosphite is a monophosphite in which each phosphorus atom is bonded to three oxygen atoms and at least one such oxygen atom is bonded to a carbon atom of an aromatic ring, which carbon atom of the ring is adjacent to another carbon atom of the ring having a pendant monovalent group (hindered group) having steric hindrance at least as great as that of an isopropyl group, and (e) a Group VII metal complex additive in an amount sufficient to increase the rate of the hydroformylation process; and (2) maintaining the reaction mixture under conditions such that the olefin compound reacts with hydrogen and carbon monoxide to form an aldehyde.

[0010] In contrast to the findings in US 4,200,592, the use of a Group VII catalyst precursor has a profound effect on the rate of reaction using a monophosphite-based catalyst (as opposed to a monophosphane-based catalyst). Without being bound by theory, this surprising difference can be related to the stronger binding properties of phosphane compared to phosphite.

[0011] These and other embodiments are discussed in more detail in the Specific Embodiments section below. DETAILED DESCRIPTION

[0012] All references to the Periodic Table of the Elements and various groups, periods and blocks thereof are based on the Periodic Table of the Elements as published by the CRC Handbook of Chemistry and Physics, 72ndEd., (1991-1992), CRC Press, p. I-11.

[0013] Unless otherwise indicated, all parts and percentages are on a weight basis, and all test methods are the most recent ones at the time of filing 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 U.S. version is so incorporated by reference) especially with respect to the disclosure of definitions (to the extent not inconsistent with definitions specifically provided in this disclosure) and general knowledge in the art.

[0014] As used herein, "a," "an," "the," and "at least one" are used interchangeably and mean one or more. When the term "comprising" or "including" or variations thereof are used in the specification, these terms are not intended to exclude any element outside the claimed subject matter. Thus, for example, an aqueous composition including "a" particulate hydrophobic polymer can be interpreted to mean that the composition includes "one or more" particulate hydrophobic polymers.

[0015] Also herein, recitation of ranges of values includes all values within the range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.). For purposes of this application, it should be understood that the numerical ranges recited are intended to include all possible sub-ranges encompassed therein. For example, a range of 1 to 100 is intended to convey a range of 1.01 to 100, 1 to 99.99, 1.01 to 99.99, 40 to 60, 1 to 55, etc. Also herein, recitation of ranges of values and / or values, including such recitation in the claims, is understood to include the term "about." In such instances, the term "about" means substantially the same as the recited range of values and / or values.

[0016] As used herein, the terms "ppm" and "ppmw" are used interchangeably and mean parts per million by weight.

[0017] For the purposes of the present invention, the term "hydrocarbon" is intended to include all permissible compounds having at least one hydrogen and one carbon atom. Such permissible compounds can 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 can be substituted or unsubstituted.

[0018] As used herein, the term "substituted" is intended to include all permissible substituents of organic compounds. In a broad aspect, permissible substituents include acyclic and cyclic, branched and unbranched, carbocyclic and heterocyclic, aromatic and non-aromatic substituents of organic compounds. Illustrative substituents include, for example, alkyl, alkoxy, aryl, aryloxy, hydroxyalkyl, aminoalkyl groups, wherein the number of carbons in the range of from 1 to 20 or more, preferably 1 to 12, and hydroxyl, halo, and amino groups. 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 way by the permissible substituents of organic compounds.

[0019] As used herein, the term "hydroformylation" or "hydroformylation process" is intended to include, but is not limited to, all hydroformylation processes involving the conversion of one or more substituted or unsubstituted olefin compounds or a reaction mixture comprising one or more substituted or unsubstituted olefin compounds to one or more substituted or unsubstituted aldehyde or a reaction mixture comprising one or more substituted or unsubstituted aldehyde. The aldehyde can be asymmetric or non-asymmetric.

[0020] The terms "reaction fluid," "reaction medium," and "catalyst solution" are used interchangeably herein and can include, but are not limited to, mixtures comprising: (a) a metal- organophosphorus ligand complexed catalyst, (b) free organophosphorus ligand, (c) aldehyde product formed in the reaction, (d) unreacted reactants, (e) solvent for the metal-organophosphorus ligand complexed catalyst and the free organophosphorus ligand, and optionally (f) soluble and / or suspended phosphorus acidic compound(s) formed in the reaction. Reaction fluid can include, but is not limited to, (a) fluid in the reaction zone, (b) fluid stream on its way to the separation zone, (c) fluid in the separation zone, (d) recycle stream, (e) fluid withdrawn from the reaction zone or separation zone, (f) treated withdrawn fluid with an acid removal system such as an extractor or other immiscible fluid contact system, (g) treated or untreated fluid returned to the reaction zone or separation zone, (h) fluid in external coolers, and (i) ligand decomposition products and components derived therefrom, such as oxides, sulfides, salts, oligomers, etc.

[0021] An "organomonophosphite ligand" is a compound containing a single phosphorus atom bonded to three oxygen atoms; each of the three oxygen atoms is otherwise bonded to a carbon moiety. At least one such oxygen atom is bonded to a carbon atom of an aromatic ring that is adjacent to another carbon atom of the ring having a pendant group monovalent group (hindered group) having steric hindrance at least as great as that of an isopropyl group. Illustrative examples include, but are not limited to, monooorganophosphite, dioorganophosphite, triorganophosphite compounds, examples of which include: tris(2,4-di-tert-butylphenyl) phosphite, 4,8-di-tert-butyl-6-(2-(tert-butyl)-4-methoxyphenyl)-2,10-dimethoxydibenzo[d,f][1,3,2]dioxaphosphepin, and the like.

[0022] The term "free ligand" refers to a ligand that is not complexed (or bonded) to a metal, e.g., a metal atom, of a complex catalyst.

[0023] For purposes of the present invention, the terms "heavy by-product" and "heavy material" are used interchangeably and refer to a liquid by-product having a normal boiling point at least 25°C greater than the normal boiling point of the desired product of the hydroformylation process. Such materials are known to form in the hydroformylation process under normal operating conditions through one or more side reactions, including, for example, through aldol condensation.

[0024] For purposes of the present invention, the term "dimer" when referring to a heavy by-product from a hydroformylation reaction refers to a heavy by-product derived from two aldehyde molecules. Likewise, the term "trimer" when referring to a heavy by-product from a hydroformylation reaction refers to a heavy by-product derived from three aldehyde molecules.

[0025] For purposes of the present invention, the terms "separation zone" and "evaporator" are used interchangeably and refer to a separation device in which the product aldehyde is typically volatilized, condensed, and collected overhead, while the non-volatile concentrated effluent (tailings or evaporator tailings) containing the homogeneous catalyst is returned to one or more reactors. The evaporator temperature is typically higher than the reactor temperature and can optionally be operated under reduced pressure. In one embodiment, the evaporator is characterized by a flowing gas of varying composition that aids in the removal of the product and optionally stabilizes the catalyst ("stripping gas evaporator"). Other separation zone methods, such as liquid / liquid extraction or membrane filtration, can also be employed.

[0026] The homogeneous olefin hydroformylation process of the present invention for producing aldehydes includes:

[0027] (1) contacting reactants comprising (a) an olefin, (b) hydrogen, and (c) CO in a reaction zone in the presence of: (d) a catalytic amount of a soluble rhodium- monophosphite-based catalyst, optionally with free organic phosphite ligand, wherein the monophosphite is one in which each phosphorus atom is bonded to three oxygen atoms and at least one such oxygen atom is bonded to a carbon atom of an aromatic ring, which carbon atom of the ring is adjacent to another carbon atom of the ring having a pendant monovalent group (hindered group) having steric hindrance at least as great as that of an isopropyl group, and (e) a Group VII metal complex additive in an amount sufficient to increase the rate of the hydroformylation process; and

[0028] (2) maintaining the reaction mixture under conditions such that the olefin compound reacts with hydrogen and carbon monoxide to form an aldehyde.

[0029] In preferred embodiments, the Group VII metal additive complex comprises a metal complex in a low oxidation state, preferably no more than +2 and most preferably no more than +1. While higher oxidation state additives can be reduced under hydroformylation conditions, the presence of such high oxidation state materials can lead to heavies formation and / or aldehyde oxidation, and thus are not preferred.

[0030] Preferred ligands on the Group VII metal additive complex are carbon and phosphorus based, such as CO, acetylacetonate, and organic phosphorus ligands (most preferred are organic phosphite ligands). The ligands are preferably substantially free of cyanide, sulfur, or halogen. The Group VII metal additive is preferably soluble in the organic matrix of the catalyst solution, thus non-ionic (neutral) complexes are generally preferred. In general, the most preferred and readily available Group VII metal additives are compounds of M x (CO) y .

[0031] The preferred Group VII metal (M) is manganese. For some embodiments, the preferred Group VII metal complex additive is Mn2(CO) 12 .

[0032] Under hydroformylation conditions, the Group VII metal additive can undergo derivatization reactions, such as M-M bond cleavage or substitution of one or more CO groups by monophosphite. The exact structure of the Group VII additive under hydroformylation conditions is unknown.

[0033] The amount of Group VII metal complex additive is not strictly critical, but is preferably in a molar ratio to the rhodium metal higher than 2:1. Ratios higher than 20:1 are generally not advantageous and can promote higher heavies formation. In some embodiments, it can be advantageous to add the Group VII metal complex additive in a ratio of 5:1 to 15:1 or even 8:1 to 12:1 compared to the rhodium metal.

[0034] Generally, such hydroformylation reactions involve the production of aldehydes by reacting olefinic unsaturated compounds with carbon monoxide and hydrogen in the presence of a rhodium-phosphite complex catalyst dissolved in a liquid medium also containing a solvent for the catalyst and free phosphite ligand (i.e., ligand not complexed with the rhodium metal in the active complex catalyst). The recycle procedure generally involves continuously or intermittently withdrawing a portion of the liquid reaction medium containing catalyst and aldehyde product from the hydroformylation reaction zone and distilling the aldehyde product from the portion in one or more stages at atmospheric, subatmospheric or elevated pressure in a separate distillation zone as appropriate to recover the aldehyde product and other volatile materials in vapor form, recycle the residue containing non-volatile rhodium catalyst to the reaction zone. Condensation of the volatilized materials can be carried out in any conventional manner and separated and recovered, e.g., by distillation, the aldehyde product if desired being subjected to further purification, and any recovered reactants, e.g., olefinic starting material and synthesis gas, being recycled to the hydroformylation zone in any desired manner. Likewise, the recovered residue containing non-volatile rhodium catalyst can be recycled to the hydroformylation zone in any desired conventional manner with or without further treatment. Thus, the general hydroformylation process in which embodiments of the present application can be practiced corresponds to any one of the known treatment techniques heretofore employed in conventional gas or liquid catalyst recycle hydroformylation reactions.

[0035] Exemplary rhodium-phosphite complex catalysts useful in such hydroformylation reactions encompassed by the present application can include, but are not limited to, those rhodium-phosphite complex catalysts disclosed in the above-mentioned patents and applications. Generally, such catalysts can be preformed or formed in situ as described in such references and consist essentially of rhodium complexed with an organic phosphite ligand. Carbon monoxide is also believed to be present and complexed with the rhodium in the active species. The active catalyst species can also contain hydrogen directly bonded to the rhodium.

[0036] Exemplary organic phosphite ligands useful as organic phosphite ligands complexed with the rhodium catalyst and / or free organic phosphite ligands in such hydroformylation reactions encompassed by the present application can include a variety of tertiary organic phosphites such as the diorganophosphites of the formula (III) wherein R 1 represents a divalent organic radical and W represents a substituted or unsubstituted monovalent hydrocarbon radical.

[0037]

[0038] R 1 in the above formula (III) include those wherein R 1 may be divalent acyclic radicals or divalent aromatic radicals. Exemplary divalent acyclic radicals are, for example, alkylene, alkylene-oxy-alkylene, alkylene-N X -alkylene (wherein each R is hydrogen or a monovalent hydrocarbon radical), alkylene-S-alkylene, and cycloalkylene radicals; and the like, such as are more fully disclosed, for example, in U.S. Pat. Nos. 3,415,906 and 4,567,306, among others. Exemplary divalent aromatic radicals are, for example, arylene, biarylene, arylene-alkylene, arylene-alkylene-arylene, arylene-oxy-arylene, arylene-oxy-alkylene, arylene-NX-arylene, and arylene-NX-alkylene (wherein X is hydrogen or a monovalent hydrocarbon radical), arylene-S-alkylene, and arylene-S-arylene radicals; and the like. More preferably, R 1 is a divalent aromatic radical.

[0039] More preferred representatives of the class of tertiary diorganophosphite esters are diorganophosphite esters of formula (IV) wherein W is a substituted or unsubstituted monovalent hydrocarbon radical, Ar is a substituted or unsubstituted aryl radical, each Ar is the same or different, each y individually has a value of 0 or 1, Q is a divalent bridging radical selected from the group consisting of --CR 3 R 4 --, --O--, --S--, --NR 5 --, SiR 6 R 7 --, and --CO-- wherein each R 3 and R 4 is independently selected from the group consisting of hydrogen, an alkyl radical having from 1 to 12 carbon atoms, phenyl, tolyl, and anisyl, wherein each R 5 , R 6 , and R 7 is independently hydrogen or a methyl radical, and n has a value of 0 or 1. Diorganophosphite esters of formula (IV) are described in more detail, for example, in U.S. Pat. Nos. 4,599,206 and 4,717,775.

[0040]

[0041]

[0042] More preferred diorganophosphite esters are those of formula (V) wherein Q is --CR1 R 2 , and each R 1 and R 2 radicals individually represent radicals selected from the group consisting of hydrogen and alkyl radicals; wherein each y individually has a value of 0 or 1, and n has a value of 0 to 1; wherein W represents an unsubstituted or substituted monovalent hydrocarbon radical selected from the group consisting of alkyl radicals having 1 to 36 carbon atoms (such as primary, secondary, and tertiary alkyl radicals, for example, methyl, ethyl, n-propyl, i-propyl, butyl, sec-butyl, t-butyl, t-butyl ethyl, t-butyl propyl, n-hexyl, pentyl, sec-pentyl, t-pentyl, iso-octyl, 2-ethylhexyl, decyl, octadecyl, and the like) and aryl radicals such as a-naphthyl, β-naphthyl, and aryl radicals of the formula (VI):

[0043]

[0044] and wherein each X 1 , X 2 , Y 1 , Y 2 , Z 2 , Z 3 , and Z 4 radicals individually represent radicals selected from the group consisting of hydrogen, alkyl radicals having 1 to 8 carbon atoms, substituted or unsubstituted aryl, alkylaryl, arylalkyl, and alicyclic radicals (for example, phenyl, benzyl, cyclohexyl, 1-methylcyclohexyl, and the like), hydroxyl (— OH) and ether (i.e., oxy) radicals such as — OR 8 , wherein R 8 is an alkyl radical having 1 to 18 carbon atoms. Other diorganophosphite esters are those of the above formula (V) as described in U.S. Patent Nos. 4,599,206, 4,717,775, and WO 2016 / 087301.

[0045] Another group of tertiary organophosphite esters useful in such hydroformylation reactions encompass by the present invention is the tertiary monoorganophosphite esters of the formula (VII) wherein Z 5 represents a trivalent organic radical such as described in more detail in, for example, U.S. Patent No. 4,567,306.

[0046]

[0047] Finally, another group of tertiary organic phosphite esters useful in the hydroformylation reactions encompassing the present application includes triorganophosphite esters such as tris(2,4-di-tert-butylphenyl) phosphite, tris(o-phenyl) phenyl phosphite, tris(o-methyl) phenyl phosphite, tris(o-tert-butyl) phenyl phosphite, and the like. Such triorganophosphite esters are described in greater detail in, for example, U.S. Patents 3,527,809, 4,717,775, and 9,737,884.

[0048] Thus, the organic phosphite ligand that can be used as the rhodium-organic phosphite complex catalyst in the hydroformylation reactions encompassing the present application and / or that is present as free organic phosphite ligand in the hydroformylation reaction medium and liquid solution throughout the hydroformylation process can be a tertiary organic phosphite ligand selected from the group consisting of mono-, di-, and tri-organic phosphite ligands, such as described above. Mixtures of tertiary organic phosphite ligands can also be employed.

[0049] The hydroformylation processes encompassing the present application can be conducted with any excess of the desired free organic phosphite ligand, for example, at least one mole of free organic phosphite ligand per mole of rhodium present in the reaction medium, up to 100 moles of free organic phosphite ligand or higher, if desired. Generally, an amount of about 4 moles to about 50 moles of organic phosphite ligand per mole of rhodium present in the reaction medium should be suitable for most purposes, said amount being the sum of both the amount of organic phosphite ligand bound (complexed) to the rhodium present and the amount of free (uncomplexed) organic phosphite ligand present. Of course, if desired, supplemental organic phosphite ligand can be supplied to the reaction medium of the hydroformylation process at any time and in any suitable manner to maintain a predetermined level of free ligand in the reaction medium. Moreover, it should be understood that while the organic phosphite ligand of the rhodium-organic phosphite complex catalyst and the excess free organic phosphite ligand in a given process are generally the same, if desired, different organic phosphite ligands can be employed for each purpose and mixtures of two or more different organic phosphite ligands can be employed in any given process.

[0050] The amount of rhodium-organophosphite complex catalyst present in the reaction medium of a given hydroformylation process encompassed by the present application need only be the minimum amount necessary to provide the given rhodium concentration desired to be employed, and will be based on at least the catalytic amount of rhodium required to catalyze the particular hydroformylation process involved, such as, for example, those disclosed in the aforementioned patents and applications. Generally, for most processes, a rhodium concentration in the range of from about 10 ppm to about 1000 ppm, calculated as free rhodium in the hydroformylation reaction medium, should be sufficient, with rhodium in the range of from about 5 ppm to 500 ppm generally preferred, and from 10 ppm to 350 ppm of rhodium more preferred.

[0051] Olefin starting material reactants useful in the hydroformylation reactions encompassed by the present application can be terminally or internally unsaturated, and have linear, branched, or cyclic structures, such as, for example, those disclosed in the aforementioned patents and applications. Such olefins can contain from 2 to 20 carbon atoms, and can contain one or more olefinic unsaturated groups. In addition, such olefins can contain groups or substituents which will not substantially interfere with the hydroformylation process, such as carbonyl, carbonyloxy, oxyl, hydroxyl, oxycarbonyl, halogen, alkoxy, aryl, alkyl, haloalkyl, and the like. Exemplary olefinically unsaturated compounds include alpha olefins, internal olefins, alkyl olefins, alkenyl alkanoates, alkenyl alkyl ethers, alkenyl alcohols, and the like, such as, for example, ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-octadecene, 2-butene, isobutylene, 2-methylbutene, 2-hexene, 3-hexene, 2-heptene, cyclohexene, propylene dimer, propylene trimer, propylene tetramer, butene dimer, butene trimer, 2-ethyl-1-hexene, styrene, 3-phenyl-1-propene, 1,4-hexadiene, 1,7-octadiene, 3-cyclohexyl-1-butene, and the like. Of course, it will be appreciated that mixtures of different olefinic starting materials can be employed, if desired. Embodiments of the present application can be particularly useful for the hydroformylation of C4and higher olefins. Thus, in some embodiments, the olefinically unsaturated starting material is an alpha olefin containing from 3 to 20 carbon atoms, and an internal olefin containing from 4 to 20 carbon atoms, as well as mixtures of such alpha olefin and internal olefin starting materials.

[0052] As noted above, the hydroformylation reactions encompassed by the present application are also conducted in the presence of an organic solvent for the rhodium-phosphite complex catalyst. Any suitable solvent which does not unduly and adversely interfere with the intended hydroformylation process can be employed. Exemplary suitable solvents for rhodium-catalyzed hydroformylation processes include, for example, those disclosed in the aforementioned patents and applications. Of course, if desired, a mixture of one or more different solvents can be employed. The most preferred solvent is one in which the olefin starting material, the hydroformylation catalyst, and the organic polymeric additive employed herein are all substantially soluble. In general, it is preferred to employ as the primary solvent an aldehyde compound corresponding to the aldehyde product desired to be produced and / or a higher boiling aldehyde liquid condensation byproduct, such as a higher boiling aldehyde liquid condensation byproduct produced in situ during the hydroformylation process. Indeed, while any suitable solvent can be employed at the beginning of a continuous process, due to the nature of such continuous processes, the primary solvent will generally end up containing both the aldehyde product and the higher boiling aldehyde liquid condensation byproduct. If desired, such aldehyde condensation byproducts can also be preformed and used accordingly. These condensation products contain polar moieties, such as esters and alcohols, but do not appear to stabilize the rhodium catalyst, thereby failing to protect against the production of clusters and gels. Of course, the amount of solvent employed is not critical to the subject application, and need only be an amount sufficient to provide the reaction medium with the particular rhodium concentration desired for a given process. In general, the amount of solvent employed can range from about 5 wt% up to about 95 wt% or more, based on the total weight of the reaction medium.

[0053] Hydroformylation reaction conditions useful in the hydroformylation processes encompassed by the present application can include any suitable continuous liquid catalyst recycle hydroformylation conditions heretofore disclosed in the above-identified patents and applications. For example, the total gas pressure of hydrogen, carbon monoxide and olefinic unsaturation starting compound of the hydroformylation process can range from about 7 kPa(a) to about 69,000 kPa(a). Generally, however, it is preferred to operate the process at a total gas pressure of hydrogen, carbon monoxide and olefinic unsaturation starting compound of less than about 10,300 kPa(a) and more preferably less than about 3,400 kPa(a). The minimum total pressure is limited primarily by the amount of reactants required to obtain the desired reaction rate. More specifically, the partial pressure of carbon monoxide of the hydroformylation process of the present application is preferably from about 7 kPa(a) to about 830 kPa(a) and more preferably from about 21 kPa(a) to about 620 kPa(a), while the partial pressure of hydrogen is preferably from about 100 kPa(a) to about 1,100 kPa(a) and more preferably from about 200 kPa(a) to about 690 kPa(a). Generally, the H2:CO molar ratio of gaseous hydrogen to carbon monoxide can range from about 1:10 to 100:1 or higher, with a more preferred hydrogen to carbon monoxide molar ratio of from about 1:1 to about 10:1. In addition, the hydroformylation process can be conducted at a reaction temperature of from about 45°C to about 150°C. Generally, a hydroformylation reaction temperature of from about 50°C to about 120°C is preferred for all types of olefinic starting materials; higher temperatures are considered less desirable as a decline in catalyst activity can occur as disclosed in, for example, U.S. Patent No. 4,599,206.

[0054] Further, as noted herein, the continuous hydroformylation process catalyzed by the dissolved rhodium-phosphite complex catalyst useful in the present application involves a liquid catalyst recycle procedure. Liquid catalyst recycle procedures of this type are known, as disclosed, for example, in the patents and applications noted above, and thus need not be described in particular detail herein, as the present application can employ any such conventional catalyst recycle procedure. For example, in such liquid catalyst recycle procedures, generally a portion of the liquid reaction product medium (containing, for example, the aldehyde product, the dissolved rhodium-phosphite complex catalyst, free phosphite ligand and organic solvent, as well as by-products produced in situ by the hydroformylation (e.g., aldehyde condensation by-products, etc.), and unreacted olefin starting material, carbon monoxide and hydrogen (synthesis gas) dissolved in the medium) is continuously withdrawn from the hydroformylation reactor to a distillation zone, e.g., a vaporizer / separator, where the desired aldehyde product is distilled in one or more stages at atmospheric, subatmospheric or elevated pressure, as appropriate, and separated from the liquid medium. The so-separated volatilized or distilled desired aldehyde product can then be condensed and recovered in any conventional manner as discussed above. The remaining non-volatilized liquid residue (further treated or not, as desired) containing the rhodium-phosphite complex catalyst, solvent, free phosphite ligand and, generally, some aldehyde product, along with any by-products and non-volatilized gas reactants that can still be dissolved in the recycle liquid residue, is then recycled back to the hydroformylation reactor in any desired conventional manner, such as disclosed, for example, in the patents and applications noted above. Further, if desired, the reactant gases so removed from the vaporizer by such distillation can also be recycled back to the reactor.

[0055] The distillation and separation of the desired aldehyde product from the product solution containing the rhodium-phosphite complex catalyst can be carried out at any suitable temperature desired. Generally, it is recommended that such distillation be carried out at low temperature, such as below 150°C, preferably below 140°C, and more preferably at a temperature in the range of from about 50°C to about 130°C. Such aldehyde distillation is generally carried out under reduced pressure, for example, significantly below the total gas pressure employed during the hydroformylation when low boiling aldehydes (e.g., C4to C6) are involved, or under vacuum when high boiling aldehydes (e.g., C7or greater) are involved. For example, it is conventional practice to subject the liquid reaction product medium removed from the hydroformylation reactor to reduced pressure in order to volatilize a substantial portion of the unreacted gases dissolved in the liquid medium, and then to move the volatilized gases and liquid medium (now containing a much lower concentration of synthesis gas than was present in the hydroformylation reaction medium) into a distillation zone (e.g., vaporizer / separator) where the desired aldehyde product is distilled. Generally, a distillation pressure ranging from vacuum pressure or lower up to a total gas pressure of about 50 psig should be sufficient for most purposes.

[0056] In some embodiments, the polymeric additives described in U.S. Patent 4,774,361 and US 11,111,198 can be used. The amount of such organic polymeric additives that can be used in any given process of the present application need only be the minimum amount required to provide a basis for at least some minimization of such rhodium loss that can be found to occur as a result of conducting the same rhodium catalyzed liquid recycle hydroformylation process under the same conditions, provided that the same process is conducted in the absence of the same organic polymer employed in the given process. For most processes, an amount of such organic polymeric additives in the range of from about 0.1 wt% up to about 3 wt% based on the total weight of fluid in the hydroformylation reaction zone should be sufficient. The upper amount of organic polymeric additive that can be used herein is primarily controlled by the solubility limit of the organic polymer in the residue containing unvolatilized liquid rhodium catalyst obtained after distilling off as much of the desired aldehyde product as possible. Generally, the amount of such organic polymeric additive will be in the range of from about 0.1 wt% to about 3.0 wt%, with about 0.25 wt% to about 2.5 wt% being desirable in some embodiments, each based on the total weight of fluid in the hydroformylation reaction zone.

[0057] The addition of Group VII metal complex additive that can be used in the present application to the hydroformylation reaction fluid can be carried out in any suitable manner that can be desired. For example, the Group VII complex can be added to the reaction fluid at any time prior to or during the production of aldehyde. Generally, it is preferred that such Group VII metal complex additive be added directly to the hydroformylation reaction fluid and that the Group VII metal complex additive be maintained in solution throughout the liquid catalyst recycle hydroformylation solution.

[0058] Some embodiments of the present application will now be described in greater detail in the following examples.

[0059] Examples

[0060] All parts and percentages in the following examples are by weight unless otherwise indicated. Pressure is given in absolute pressure unless otherwise indicated.

[0061] General procedure: Single pass hydroformylation procedure :

[0062] Hydroformylation experiments (glass reactor) were performed to compare the reaction rate of tris-(2,4-di-tert-butylphenyl) phosphite (Ligand A) in the presence or absence of a Group VII metal. To evaluate catalyst performance, a 90 ml Fisher Porter bottle equipped with a sampling port, inlet / outlet valves, and a pressure gauge was used as the reaction vessel. Unless otherwise indicated, the Fisher Porter bottle was first inertized with N2and heated in a temperature controlled oil bath. A solution of 25 ppm rhodium and 2 wt% Ligand A in tetraglyme was charged and operated under the conditions described in Table 1 below.

[0063] After sealing the reactor, the system was purged with nitrogen and the oil bath was heated to provide the desired hydroformylation reaction temperature. The hydroformylation reaction was conducted at a total pressure of 150 psig to 160 psig (1034 kPa to 1103 kPa) and a temperature ranging from 60 °C to 100 °C. The feed comprising nitrogen, syngas, and propylene was started. The flow of the feed gases (H2, CO, propylene, N2) was individually controlled with mass flow meters as indicated in Table 1, and the feed gases were dispersed in the catalyst precursor solution via a sintered metal distributor. The partial pressures of N2, H2, CO, propylene, and aldehyde product were determined by GC analysis and Dalton's law analysis of the effluent stream. The unreacted portion of the feed gases was stripped out with the nitrogen stream along with the butyraldehyde product to maintain an essentially constant liquid level. The flow rates and feed gas partial pressures were set to achieve a hydroformylation reaction rate of about 2 gram-moles of aldehyde per liter of reaction fluid per hour. In practice, it was often observed that it took the system about one day to reach steady state conditions due to the removal of trace amounts of air from the feed lines and to reach thermal equilibrium of the oil bath or other substantial changes in process variables.

[0064] The reaction was started in the absence of a Group VII metal. After 5 days, a solution of dodecacarbonylmanganese in toluene was added at a 10: 1 molar ratio of Mn / Rh. The results are presented below:

[0065] Table 1: Operating conditions for single pass hydroformylation performance test.

[0066]

[0067] Figure 1

[0068] The initial phase is a typical phase for this fresh catalyst system in the absence of known poisons or inhibitors. Once the manganese compound is added, the rate increases and remains stable, which results in a decrease in propylene partial pressure. Since the rate is approximately first order with respect to olefin concentration, in order to be able to compare rates, the olefin partial pressure is increased to that of the control (initial) phase. After readjusting the propylene partial pressure, the rate has increased from 1.6 gmol / L / hr to 2.8 gmol / L / hr, providing a 75% rate increase.

Claims

1. A method for the hydroformylation of homogeneous olefins for the production of aldehydes, the method comprising: Reactants comprising olefins, hydrogen, and CO are contacted in a reaction zone in the presence of a rhodium-based organic phosphite catalyst and a soluble Group VII metal complex additive, wherein the Group VII metal complex additive is present in a molar ratio greater than 2:1 to rhodium.

2. The method of claim 1, wherein the olefin has four or more carbon atoms.

3. The method of claim 1, wherein the olefin has eight or more carbon atoms.

4. The method of claim 1, wherein the Group VII metal in the Group VII metal complex additive is manganese.

5. The method according to claim 1, wherein the group VII metal complex additive is nonionic.

6. The method of claim 1, wherein the group VII metal complex additive is substantially free of halogens, sulfur and cyanides.

7. The method according to claim 1, wherein the group VII complex additive is added in an amount such that the ratio of the group VII complex additive to rhodium is in the range of 5:1 to 15:

1.

8. The method according to claim 1, wherein, in addition to the rhodium-organophosphite-based catalyst and the Group VII metal complex additive, the reactants are contacted in the presence of a free organic phosphite ligand.

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