Method for minimizing use of polyphosphines by utilizing degradation products

Abstract

The present invention relates, in part, to a method for slowing polyphosphine ligand usage in a hydroformylation process. It has been found that the usage of polyphosphine ligands can be reduced when a target concentration of total polyphosphorus compounds comprising the polyphosphine ligands and polydentate ligand degradation products is maintained in the reaction zone.

Description

Technical Field

[0001] The present invention relates to catalyst compositions and methods of using such compositions to reduce the use of polyphosphine ligands in hydroformylation processes. Background Art

[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-triorganophosphine ligand complex catalyst, and preferred types of such processes include continuous hydroformylation. For example, U.S. Patent No. 3,527,809 discloses the hydroformylation of α-olefins at low temperature and low pressure to produce aldehydes. This process employs certain rhodium complexes to effectively catalyze the hydroformylation of olefins with hydrogen and carbon monoxide in the presence of a selected triorganophosphine ligand under a set of defined variables.

[0003] Among the catalysts described in U.S. Patent No. 3,527,809 are compounds containing rhodium and triarylphosphine ligands, particularly triarylphosphine ligands exemplified by triphenylphosphine (“TPP”). Commercial hydroformylation processes have successfully employed rhodium-TPP catalysts for decades, and a key aspect of the operation is the use of a large excess of TPP relative to rhodium. For example, industrial propylene hydroformylation processes typically operate at a TPP concentration of 10 wt% - 12 wt% based on the total mass of the reaction fluid. Such a high concentration of TPP is used to achieve the desired product regioselectivity and enhance catalyst stability.

[0004] Over time, hydroformylation catalysts tend to deactivate for a variety of reasons, including rhodium aggregation or the presence of inhibitory compounds. Steps can be taken to maintain production targets, such as increasing the rhodium concentration, raising the reaction temperature, or catalyst regeneration treatments such as the procedures taught in U.S. Patent No. 5,237,106. Despite these efforts, the catalyst eventually reaches a point of deactivation where it is no longer useful for commercial purposes. These “end-of-life” catalysts must be removed from the process, sent for precious metal recovery (PMR), and replaced with fresh rhodium and ligand charges. The costs associated with PMR, replacing the entire rhodium and ligand inventory, and production losses during catalyst replacement can be substantial.

[0005] The hydroformylation process using C3 and higher olefins produces a mixture of linear (n) and branched (iso) aldehydes; the regioselectivity is usually expressed as the ratio of n-aldehyde to iso-aldehyde (N / I). Although both products are useful, the linear isomer generally has greater value in the market; thus, it is usually desirable to produce a higher N / I ratio. It is well known that catalysts capable of producing an N / I of greater than about 10-12 consist of chelating ligands containing at least two phosphorus moieties (see, for example, "Rhodium Catalyzed Hydroformylation", Kluwer Academic Publishers, 2000). In general, chelating ligands include polyphosphines, polyphosphites, polyphosphinamides, etc. Specific examples include, but are not limited to, triphosphines (such as those described in WO2018103536) and tetraphosphine ligands (such as those described in U.S. Patent No. 7,531,698 and U.S. Patent No. 9,687,837).

[0006] Such chelating ligands are generally prepared via custom synthesis, which increases their cost. In general, the required amount of chelating ligand in the catalyst solution is greater than one molar equivalent relative to the catalytic metal to ensure good performance (such as an N / I value higher than 10) and no loss of catalytic metal; the typical range is 1.2 moles to 5 moles of chelating ligand per mole of metal, and the optimal ratio to achieve a balance between performance and cost is usually about 3 moles of chelating ligand per mole of metal.

[0007] It is known that chelating ligands degrade during continuous operation due to oxidation, hydrolysis, or rhodium-promoted side reactions such as aryl cleavage. Many prior arts teach means for removing these degradation products, as many degradation products are catalyst poisons or inhibitors (US4605780, US4861918, and US5364950) or contribute to autocatalytic ligand degradation. US4260828 teaches that one such inhibitory ligand degradation product (alkyl-diarylphosphine, R-P(Ar)2) can be used to mitigate further loss of activity, but the inhibited catalyst exhibits a lower hydroformylation rate; thus, more severe operating conditions must be used, which tend to produce more heavy by-products.

[0008] Because if the concentration of the chelating ligand drops below one molar equivalent relative to rhodium, rhodium metering, hydroformylation rate, and / or product regioselectivity will be affected, it is common practice to replenish these compounds to maintain the desired performance. The rate at which the chelating ligand must be added to the system to maintain the target concentration ("ligand usage rate") is a key economic factor because chelating ligands are typically expensive custom compounds. For example, in a continuous hydroformylation process involving a chelating polyphosphine, the goal will be to maintain the polyphosphine:rhodium ratio at an optimized target of approximately 3:1. Maintaining this polyphosphine:rhodium ratio involves continuously adding expensive polyphosphine ligands to compensate for the cost of polyphosphine degradation.

[0009] US11130725 teaches adding a monophosphine to a catalyst comprising rhodium and a tetraphosphine ligand to enhance catalyst stability. US11344869 also teaches that the ratio of tetraphosphine and / or monophosphine to the catalytic metal can be used to intentionally control N / I.

[0010] Although ligand degradation is significant in batch mode operation, tetradentate-substituted phosphine derivatives have been shown to be able to continue hydroformylation, but no reaction rate and N / I performance data are provided (Fanding Zhou, Lin Zhang, Qianhui Wu, Fuya Guo, Songbai Tang, Bin Xu, Maolin Yuan, Haiyan Fu, Ruixiang Li, Xueli Zheng, Hua Chen, *Appl Organometal Chem.*, 2019, Vol. 33: e4646). Ligand degradation is reported to occur during batch distillation, so no teachings are provided on how to maintain stable performance in a continuous hydroformylation process.

[0011] There is a need for a method for slowing down or reducing the ligand usage rate in a high N / I hydroformylation process involving polyphosphines. SUMMARY OF THE INVENTION

[0012] The present invention relates to slowing down the polyphosphine ligand usage rate in a hydroformylation process. It has surprisingly been found that the polyphosphine ligand usage rate can be reduced when maintaining the target concentration of the total polyphosphorus compounds comprising the polyphosphine ligand and the polydentate ligand degradation products in the reaction zone.

[0013] In one embodiment, a method for slowing down the polyphosphine ligand usage rate in a hydroformylation process comprises:

[0014] (a) contacting an olefin with carbon monoxide, hydrogen, and a catalyst comprising (A) a transition metal; (B) a polyphosphine having the following structure:

[0015]

[0016] wherein each P is a phosphorus atom, and R 1 -R 20 each of which is independently hydrogen, a C1 to C8 alkyl group, a C1 to C8 alkoxy group, an aryl group, an alkaryl group, or a halogen, and R 47 and R 48 are independently hydrogen, a C1 to C8 alkyl group, or a C1 to C8 substituted alkyl group; n is 0 or 1, m is 2 or greater, and Q is an m+1 valent organic group, wherein R 5 and R 6 and R 15 and R 16 can be linking groups that form a bridging structure; and optionally (C) a monophosphine having the following structure:

[0017]

[0018] wherein P is a phosphorus atom, and Y 1 -Y 3 each of which is independently an aryl group or a substituted aryl group, are contacted in one or more reaction zones and carried out under hydroformylation conditions; and

[0019] (b) monitoring the content of the total polyphosphorus compound; and

[0020] (c) adjusting the feed rate of the polyphosphine ligand to maintain the total polyphosphorus compound concentration at a target value relative to the number of moles of the transition metal.

[0021] The structure of the organic group Q moiety is not particularly critical to the present invention, except that the position of the phosphorus moieties is such that they can coordinate with the catalyst metal in a chelating manner. Preferably, there should be no more than 10 bonds between the phosphorus atoms. Rigid groups such as naphthyl and biphenyl moieties can introduce additional limitations related to chelating ability, as is well known in the art. A preferred structure for Q is a tetrasubstituted biphenyl group, and most preferably having phosphorus moieties in the 2,2’,6,6’-isomer positions.

[0022] The organic group Q is different from and not intended to be part of an insoluble polymeric resin, as such supported catalysts are incompatible with the present invention because there is no continuous addition of polymeric ligands as described in our method.

[0023] In some embodiments, the preferred range for the value of m is from 3 to 10, preferably less than 6. In some preferred embodiments, m is 3 or 4.

[0024] In one embodiment, a method for slowing the usage rate of the polyphosphine ligand in a hydroformylation process comprises the same method as in the previous embodiment, except that the monophosphine of formula II is not used.

[0025] In one embodiment, a method for slowing down the use of polyphosphine ligands in a hydroformylation process comprises:

[0026] (a) contacting an olefin with carbon monoxide, hydrogen and a catalyst comprising (A) a transition metal

[0027] Genus; (B) tetraphosphine having the following structure:

[0028]

[0029] Where each P is a phosphorus atom, and R 1 To R 46 Each of which is independently hydrogen, a C1 to C8 alkyl group, an aryl group, an alkaryl group or a halogen, and optionally (C) a monophosphine having the following structure:

[0030]

[0031] Where P is a phosphorus atom, and Y 1 -Y 3 each of which is independently an aryl group or a substituted aryl group, contacted in one or more reaction zones and under hydroformylation conditions; and

[0032] (b) monitoring the content of total polyphosphorus compounds; and

[0033] (c) adjusting the feed rate of the polyphosphine ligand to maintain the sum of the total polyphosphorus compounds at 1:1 relative to

[0034] The set value for the number of moles of transition metal.

[0035] In one embodiment, a method for slowing down the use of polyphosphine ligands in a hydroformylation process comprises:

[0036] (a) contacting an olefin with carbon monoxide, hydrogen and a catalyst comprising (A) a transition metal; and (B) a tetrakisphosphine having the following structure:

[0037]

[0038] (b) adding triphenylphosphine to the reaction zone; and

[0039] (c) monitoring the content of total polyphosphorus compounds and polyphosphine ligands; and

[0040] (d) adjusting the feed rate of the polyphosphine ligand to maintain the total polyphosphorus compound at a set value in moles relative to the transition metal.

[0041] In one embodiment, a method for slowing down the use of polyphosphine ligands in a hydroformylation process comprises:

[0042] a. Contact an olefin with carbon monoxide, hydrogen, and a catalyst comprising (A) a transition metal; (B) a triarylphosphine having the following structure:

[0043]

[0044] wherein P is a phosphorus atom, and each of Y 1 -Y 3 is independently an aryl group or a substituted aryl group, and the contact is carried out in one or more reaction zones and under hydroformylation conditions;

[0046] b. Add a tetraphosphine having the following structure:

[0047]

[0048] (c) Monitor the content of total polyphosphorus compounds and polyphosphine ligands; and

[0049] (d) Adjust the feed rate of the polyphosphine ligand to maintain the total polyphosphorus compound at a set value relative to the molar amount of the transition metal.

[0050] In some embodiments, the transition metal is rhodium and the monophosphine is triphenylphosphine. These and other embodiments are discussed in more detail in the following detailed description. Detailed Description

[0051] All references to the Periodic Table of the Elements and the various groups therein are to the version published in the CRC Handbook of Chemistry and Physics, 72nd Edition, (1991 - 1992), CRC Press, page I - 11. Unless otherwise indicated or implied from the context, all parts and percentages are by weight, and all test methods are the latest as of the filing date of this application. For the purposes of U.S. patent practice, any patent, patent application, or published content mentioned is hereby incorporated by reference in its entirety (or the equivalent U.S. version is incorporated by reference in this manner), especially the disclosures regarding definitions in the art (to the extent not inconsistent with any definitions specifically provided in this disclosure) and common general knowledge.

[0052] As used herein, the terms "a", "an", "the", "at least one", and "one or more" may be used interchangeably. When the terms "comprising", "including", and variations thereof appear in the specification and claims, these terms are not intended to be limiting. Also herein, a numerical range recited by endpoints includes all numbers subsumed within 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 present invention, it is to be understood that, consistent with what is understood by a person of ordinary skill in the art, a numerical range is intended to include and support all possible sub-ranges subsumed within that range. For example, a range from 1 to 100 is intended to convey ranges 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. Additionally herein, a numerical range and / or a recitation of a numerical value, including such recitations in the claims, may be understood to include the term "about". In such cases, the term "about" refers to a numerical range and / or a numerical value that is substantially the same as the numerical range and / or numerical value recited herein.

[0053] As used herein, the term "ppmw" means parts per million by weight.

[0054] For the purposes of the present invention, the term "hydrocarbon" is intended to include all permitted compounds having at least one hydrogen and one carbon atom. Such permitted compounds may also have one or more heteroatoms. In a broad sense, permitted hydrocarbons include acyclic (with or without heteroatoms) and cyclic, branched and unbranched, carbocyclic and heterocyclic, aromatic and non-aromatic organic compounds that may be substituted or unsubstituted.

[0055] As used herein, unless otherwise indicated, the term "substituted" is intended to include all permitted substituents of organic compounds. In a broad sense, permitted 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, where the number of carbons may range from 1 to 20 or more, preferably 1 to 12, as well as hydroxy, halo, and amino. For suitable organic compounds, permitted substituents may be one or more and may be the same or different. The present invention is not intended to be limited in any way by the permitted substituents of organic compounds.

[0056] As used herein, the term "hydroformylation" is intended to include, but is not limited to, all hydroformylation processes involving the conversion of one or more substituted or unsubstituted olefinic compounds or a reaction mixture comprising one or more substituted or unsubstituted olefinic compounds into one or more substituted or unsubstituted aldehydes or a reaction mixture comprising one or more substituted or unsubstituted aldehydes. The aldehydes can be asymmetric or non-asymmetric.

[0057] 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 transition metal-monophosphine complex catalyst (e.g., a rhodium-triphenylphosphine complex catalyst), (b) a transition metal-polyphosphine ligand complex catalyst (e.g., a rhodium-polyphosphine ligand complex catalyst), (c) free monophosphine (e.g., triphenylphosphine), (d) free polyphosphine, (e) aldehyde products formed in the reaction, including condensation products (the "heavies") derived therefrom, (f) unreacted reactants, (g) a solvent for the transition metal complex catalyst and the free phosphine ligand, and optionally (h) monophosphine ligand and polyphosphine ligand degradation products. The reaction fluid can encompass, but is not limited to, (a) the fluid in the reaction zone, (b) the fluid stream on its way to the separation zone, (c) the fluid in the separation zone, (d) the recycle stream, (e) the fluid discharged from the reaction zone or the separation zone, (f) the fluid in an external cooler, and (g) the ligand degradation products.

[0058] As used herein, the term "polyphosphine ligand" is intended to include compounds having three or more P(III) phosphine moieties capable of binding to a catalytic metal as described in formula I. In one embodiment, the polyphosphine ligand is a tetraphosphine as described in formula III. The polyphosphine ligand is preferably a custom compound intentionally added to the process.

[0059] As used herein, the terms "ligand degradation" and "ligand decomposition" are used interchangeably and are intended to include the chemical transformation of polyphosphine ligands or polydentate ligand degradation products within the reaction fluid. In some embodiments, ligand degradation includes the chemical transformation of triarylphosphines that have been added to the process. Such chemical transformations include, but are not limited to, the oxidation of the phosphine moiety and rhodium-promoted side reactions (e.g., aryl-alkyl group exchange, aryl group cleavage), etc.

[0060] As used herein, the term "entrainment" is intended to include the physical discharge of the catalyst solution from the system. Such discharges can include, but are not limited to, mist and droplets entrained in the product stream in the product-catalyst separation zone.

[0061] As used herein, the terms "ligand consumption" and "consumed ligand" are used interchangeably and are intended to include a decrease in the concentration of the ligand within the catalyst solution. The ligand concentration can decrease for a variety of reasons, including but not limited to ligand degradation and entrainment. Examples of polyphosphine degradation include oxidation and P-C cleavage processes such as those described for triarylphosphines in Abatjoglou AG, Billig E, Bryant DR, Mechanism of rhodium-promoted triphenylphosphine reaction in hydroformylation processes promoted triphenylphosphine reaction in hydroformylation processes , *Organometallics* (1984), Vol. 3, pp. 923–926. Without being bound by theory and not intended to present an exhaustive list, the potential degradation products of a typical tetraphosphine ligand (Formula IV below) are shown below:

[0062]

[0063]

[0064] As used herein, the term "polydentate ligand degradation product" is intended to include all compounds containing at least two P(III) phosphine moieties that are produced by ligand degradation of a polyphosphine ligand and subsequent further degradation of the initial polydentate ligand degradation products.

[0065] As used herein, the term "polydentate ligand degradation product consumption rate" is intended to include the rate at which the concentration of the polydentate ligand degradation product decreases in the system. The concentration of the polydentate ligand degradation product can decrease for a variety of reasons, including but not limited to ligand degradation and entrainment.

[0066] As used herein, the term "monodentate ligand degradation product" is intended to include all compounds containing one phosphorus moiety that are produced by ligand degradation of a polyphosphine ligand. In some embodiments, the monodentate ligand degradation products can be derived from the chemical transformation of a triarylphosphine that has been added to the catalyst solution.

[0067] The term "triarylphosphine" is intended to include compounds as described in Formula II, which are optionally added to the process in some embodiments.

[0068] As used herein, the term "total polyphosphorus compound" is intended to include polyphosphine ligands (Formula I) and polydentate ligand degradation products (Formula I degradation products).

[0069] As used herein, the term "polyphosphine ligand feed rate" is intended to include the rate at which polyphosphine ligand must be added to compensate for polyphosphine ligand consumption and thereby maintain a target concentration in the process.

[0070] The term "polyphosphine ligand usage rate" is expected to include the material balance of the polyphosphine ligand within the process over a given time period. For example, the concentration of the polyphosphine ligand at the start of the time period under discussion is determined via analysis, and the polyphosphine ligand feed rate is measured during that time period; analyzing the process fluid at the end of the time period to determine the concentration of the polyphosphine ligand still present in the unit will allow calculation of the amount that has been consumed. In one embodiment, the polyphosphine ligand usage is expressed as the mass of polyphosphine ligand consumed per unit time per liter of process volume (e.g., grams of ligand per liter of process fluid per day; g / L-day).

[0071] As used herein, the terms "rhodium complex", "rhodium complex catalyst", and "catalyst complex" are used interchangeably and are expected to include at least one rhodium atom having ligands bound or coordinated via electronic interaction. Examples of such ligands include, but are not limited to, monophosphine ligands (if present), polyphosphine ligands, polydentate ligand degradation products, carbon monoxide, olefins (e.g., propylene), and hydrogen. In some embodiments, triarylphosphine is added as a ligand to the process.

[0072] As used herein, the term "free ligand" is expected to include, but is not limited to, monophosphine ligand degradation products, polyphosphine ligands, polydentate ligand degradation products not bound or coordinated to rhodium. In some embodiments, the free ligand will include triarylphosphine not bound or coordinated to rhodium.

[0073] As used herein, the terms "deactivation" and "catalyst deactivation" are used interchangeably and are expected to include a decrease in the hydroformylation rate over time. For example, the aldehyde production rate under comparable process conditions is measured periodically over a period of weeks (e.g., pounds of product per hour measured by determining the amount of aldehyde in the stream leaving the reactor at a constant flow rate using gas chromatography). A decrease in the amount of aldehyde produced will indicate catalyst deactivation.

[0074] The concentrations of polyphosphine ligands and polydentate ligand degradation products in the reaction fluid should be measured regularly (e.g., daily, several times a week, etc.). High performance liquid chromatography (HPLC) is the preferred measurement method.

[0075] Importantly, the analytical method used to determine ligand concentration is capable of detecting and quantifying polyphosphine ligands and polydentate ligand degradation products such that the sum can be easily calculated. The method does not need to be able to distinguish the exact structure of the degradation products (e.g., which phosphine has been oxidized, just that one being oxidized is sufficient). Calibration of HPLC analysis can be performed using HPLC-MS techniques, where the mass spectra of the peaks can be used to elucidate the degradation products, or preparative scale HPLC can be used to separate the degradation products, and mass spectrometry and 31 PNMR techniques can be used to further confirm the degradation product structure. Offline generation of degraded ligands for HPLC calibration is the preferred method. Phosphorus NMR techniques can also be used.

[0076] The concentration of the catalytic metal can be measured by conventional methods such as atomic absorption (AA), inductively coupled plasma (ICP), X-ray fluorescence (XRF).

[0077] The N / I ratio is typically determined by gas chromatography (GC) analysis of the product aldehyde; such techniques are well known in the art.

[0078] The addition of the polyphosphine ligand can be continuous (i.e., a slow, substantially continuous ligand feed) or batchwise. Preferably, the polyphosphine ligand is dissolved in a suitable solvent such as described herein, but most preferably in the product aldehyde.

[0079] The rate of polyphosphine ligand feed is adjusted to achieve the target polyphosphine ligand to catalytic metal ratio. The appropriate feed rate can be calculated based on the current concentration of the polyphosphine ligand in the system and the polyphosphine ligand usage rate. For example, if the target concentration of the polyphosphine ligand is higher than the current concentration, the polyphosphine ligand feed rate should exceed the polyphosphine ligand usage rate. Conversely, if the target concentration of the polydentate ligand is lower than the current concentration, the polydentate ligand feed rate should be lower than the usage rate.

[0080] Similarly, by adjusting the feed rate of the polyphosphine ligand, the total polyphosphorus compound:catalytic metal ratio is maintained at the target level.

[0081] If the concentration of the polyphosphine ligand is maintained within the target range, the method of ligand addition is not very critical to the present invention. In practice, there will be some inevitable fluctuations in the addition rate due to various reasons, including analytical or equipment variations, etc. Similarly, batch mode addition can produce a "sawtooth" pattern, but generally preferably, the concentration of the polyphosphine ligand is maintained within a relatively narrow range. The usage of the polyphosphine ligand will also vary slightly depending on the actual plant equipment, operating parameters (and their variations such as reactor temperature and reagent partial pressure), but those skilled in the art will be able to adjust the polyphosphine ligand addition rate to maintain its target polyphosphine ligand to catalytic metal ratio.

[0082] Surprisingly, it has been found that maintaining a favorable balance of the total polyphosphorus compound consisting of the polyphosphine ligand and the degradation products of the polydentate ligand in the catalyst solution will allow the desired hydroformylation performance to be achieved while reducing the usage rate of the polyphosphine ligand.

[0083] Without wishing to be bound by theory, it is proposed that the degradation products of the multidentate ligand sufficiently promote hydroformylation to allow the target concentration of the polyphosphine ligand to be reduced to more than the concentration typically maintained in a hydroformylation process comprising rhodium and a chelating ligand (e.g., less than one equivalent relative to rhodium). The degradation rate of the polyphosphine ligand is concentration-dependent; thus, reducing its concentration will slow down the consumption of the polyphosphine ligand. Since the multidentate ligand degradation products are derived from polyphosphine degradation, the formation rate of these compounds will slow down as the degradation of the polyphosphine ligand decreases. However, the multidentate ligand degradation products will also continue to be consumed, mainly due to rhodium-promoted side reactions. If the addition of the polyphosphine ligand is stopped or overly reduced, the concentration of the total polyphosphorus compounds in the catalyst solution will eventually be insufficient to provide the desired catalysis. Therefore, actions must be taken to achieve the results of the present invention, namely favorable hydroformylation performance and lower polyphosphine ligand usage.

[0084] To avoid the loss of the transition metal into an inactive form, such as a cluster or plating out on the reactor surface, the total molar amount of the chelating ligand (e.g., the total polyphosphorus compound) and optionally the triarylphosphine must be at least equal to and preferably exceed the molar amount of the transition metal.

[0085] In one embodiment, the polyphosphine addition rate is adjusted to maintain a total polyphosphorus compound:rhodium ratio in the catalyst solution of about 1.5:1. In another embodiment, the target for the total polyphosphorus compound:rhodium ratio is about 2:1. In another embodiment, the target for the total polyphosphorus compound:rhodium ratio is about 3:1.

[0086] In one embodiment, the total polyphosphorus compound comprises at least one polyphosphine and at least one multidentate ligand degradation product, wherein there is less than 1 equivalent of the polyphosphine ligand relative to rhodium. In another embodiment, the polyphosphine ligand:rhodium ratio ≥ 0.25:1.

[0087] In one embodiment, the N / I of the product obtained by the process is greater than 12, or even 15.

[0088] The catalyst performance will provide an indirect measurement of the relative concentrations of the polyphosphine ligand and the multidentate ligand degradation compounds that make up the total polyphosphorus compound. A decrease in N / I may indicate that the polyphosphine ligand:rhodium ratio and / or the total polyphosphorus compound concentration has dropped below the target; this can be remedied by increasing the polyphosphine ligand feed rate.

[0089] In one aspect, the present invention relates to a hydroformylation catalyst composition comprising:

[0090] (a) a polyphosphine having the following structure:

[0091]

[0092] wherein each P is a phosphorus atom, and R1 -R 20 Each of which is independently hydrogen, a C1-C8 alkyl group, a C1-C8 alkoxy group, an aryl group, an alkaryl group or a halogen, R 47 and R 48 are independently hydrogen, a C1-C8 alkyl group or a C1-C8 substituted alkyl group, n is 0 or 1, m is 2 or higher, and Q is an (m + 1)-valent organic group, where R 5 and R 6 and / or R 15 and R 16 can be a linking group forming a bridging structure; and

[0093] (b) a polyphosphine degradation product derived from the polyphosphine of formula I, wherein the molar ratio of the polyphosphine degradation product to formula I is at least 0.25:1; and

[0094] (c) Group 8, 9, and 10 transition metals;

[0095] (d) a solvent containing product aldehydes and aldehyde condensation products;

[0096] (e) Optionally, a monophosphine having the following structure:

[0097]

[0098] wherein P is a phosphorus atom, and each of Y 1 -Y 3 is independently an aryl group or a substituted aryl group,

[0099] wherein the sum of formula I and the formula I degradation product is greater than 1.1:1 relative to the number of moles of the transition metal,

[0100] and the molar ratio of formula I to the transition metal is less than 1:1.

[0101] Another aspect of the present invention is a general method for slowing down the use of polyphosphine ligands in a hydroformylation process. The catalyst comprises a catalyst composition derived from a transition metal (e.g., rhodium), a polyphosphine ligand, and a polyphosphine ligand degradation product, such that the polyphosphine degradation product is present in an amount sufficient to reduce the polyphosphine ligand feed rate.

[0102] In one embodiment, the present invention relates to a method for reducing the use of polyphosphine ligands in a hydroformylation process, the method comprising:

[0103] (a) contacting an olefin with carbon monoxide, hydrogen, and a catalyst comprising (A) a transition metal; (B) a tetraphosphine having the following structure:

[0104]

[0105] where each P is a phosphorus atom, and R 1 -R 20 each of which is independently hydrogen, a C1 to C8 alkyl group, an aryl group, an alkaryl group, or a halogen, and R 47 and R 48 are independently hydrogen, a C1 to C8 alkyl group, or a C1 to C8 substituted alkyl group, where R 5 and R 6 and R 15 and R 16 can be a linking group forming a bridging structure, each n is zero or one, and m is 2 or

[0106] higher; and

[0107] (b) optionally, a triarylphosphine having the following structure:

[0108]

[0109] where P is a phosphorus atom, and Y 1 -Y 3 each of which is independently an aryl group or a substituted aryl group, contacting in one or more reaction zones and undergoing

[0110] hydroformylation conditions; and

[0111] (c) monitoring the content of the total polyphosphorus compound and adjusting the feed rate of the polyphosphine ligand to maintain the concentration of the total polyphosphorus compound at a target value greater than 1.25:1 relative to the transition metal moles,

[0112] and where the polyphosphine ligand to catalyst metal mole ratio is less than 1:1.

[0113] In some embodiments, it may be advantageous to ensure that the polyphosphine ligand to transition metal ratio is greater than 0.25:1.

[0114] In one embodiment, the present invention relates to a method for reducing the use of polyphosphine ligands in a hydroformylation process, the method comprising:

[0115] (a) contacting an olefin with carbon monoxide, hydrogen, and a catalyst comprising (A) a transition metal; (B) a tetraphosphine having the following structure:

[0116]

[0117] where each P is a phosphorus atom, and R 1 to R 46 each of which is independently hydrogen, a C1 to C8 alkyl group, an aryl group, an alkaryl group, or a halogen; and

[0118] (b) Optionally, a triarylphosphine having the following structure:

[0119]

[0120] wherein P is a phosphorus atom, and each of Y 1 -Y 3 is independently an aryl group or a substituted aryl group, contacting in one or more reaction zones and proceeding under hydroformylation conditions; and

[0121] and

[0122] (b) Monitoring the content of total polyphosphorus compounds and adjusting the feed rate of the polyphosphine ligand to maintain the concentration of the total polyphosphorus compounds at a target value greater than 1.25:1 relative to the moles of transition metal,

[0123] and wherein the ratio of the polyphosphine ligand to the catalyst metal is less than 1:1.

[0124] In one embodiment, the present invention relates to a method for reducing the use of polyphosphine ligands in a hydroformylation process, the method comprising:

[0125] (a) Contacting an olefin with carbon monoxide, hydrogen, and a catalyst, the catalyst comprising (a) a transition metal; (b) a tetraphosphine having the following structure:

[0126]

[0127] and

[0128] (c) a triarylphosphine having the following structure:

[0129]

[0130] wherein P is a phosphorus atom, and each of Y 1 -Y 3 is independently an aryl group or a substituted aryl group, contacting in one or more reaction zones and proceeding under hydroformylation conditions; and

[0131] and

[0132] (b) Monitoring the content of total polyphosphorus compounds and adjusting the feed rate of the polyphosphine ligand to maintain the concentration of the total polyphosphorus compounds at a target value greater than 1.25:1 relative to the moles of transition metal,

[0133] and wherein the ratio of the polyphosphine ligand to the catalyst metal is less than 1:1.

[0134] In some embodiments, the transition metal includes rhodium. In some embodiments, the olefin is propylene. In some embodiments, the triarylphosphine is 3, 10 or even 20 moles of triarylphosphine per mole of transition metal, up to 350, 375 or even 400 moles of triarylphosphine per mole of transition metal.

[0135] In some embodiments, the triarylphosphine is one or more of the following: triphenylphosphine, tris(o-tolyl)phosphine, tris(naphthyl)phosphine, tris(p-methoxyphenyl)phosphine, and tris(m-chlorophenyl)phosphine. In some embodiments, the triarylphosphine is triphenylphosphine. In some embodiments, the catalyst comprises a mixture of different types of triarylphosphines.

[0136] In some embodiments, each of the R 1 -R 46 in the polyphosphine of Formula III is hydrogen. In some embodiments, the catalyst comprises one or more of the following tetraphosphines:

[0137]

[0138] In some embodiments, the transition metal includes rhodium, the triarylphosphine of Formula II is triphenylphosphine, each of the R 1 -R 46 is hydrogen, and the olefin includes propylene.

[0139] Hydrogen and carbon monoxide can be obtained from any suitable source, which includes petroleum cracking and refinery operations. Syngas (from synthesis gas) is the name given to a gas mixture containing varying amounts of CO and H2. The production methods are well known. Hydrogen and CO are usually the main components of syngas, but syngas can contain CO2 and inert gases such as N2 and Ar. The molar ratio of H2 to CO varies widely, but generally ranges from 1:100 to 100:1, and preferably between 1:10 and 10:1. Syngas is commercially available and is commonly used as a fuel source or as an intermediate for the production of other chemicals. The most preferred H2:CO molar ratio for chemical production is between 3:1 and 1:3, and for most hydroformylation applications the target is typically between about 1:2 and 2:1. The syngas mixture is the preferred source of hydrogen and CO.

[0140] The olefin starting material reactants useful in the hydroformylation reactions encompassed by this invention can be terminal or internal unsaturated and can have a straight-chain, branched-chain, or cyclic structure. Such olefins can contain from 2 to 20 carbon atoms (C2-C20) and can contain one or more ethylenic unsaturated groups. Additionally, such olefins can contain groups or substituents that do not substantially and detrimentally interfere with the hydroformylation process, such as carbonyl, carbonyloxy, oxy, hydroxy, oxycarbonyl, halogen, alkoxy, aryl, alkyl, haloalkyl, and the like. Illustrative olefinically unsaturated compounds include alpha olefins, internal olefins, alkyl acrylate esters, alkenyl alkanoate esters, alkenyl alkyl ethers, enols, etc., such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-octadecene, 2-butene, isobutene, 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 should be understood that mixtures of different olefin starting materials can be employed if desired. Embodiments of the present invention can be particularly useful for the hydroformylation of C3 and higher olefins. Thus, in some embodiments, the ethylenically unsaturated starting material is an alpha olefin containing from 3 to 20 carbon atoms, an internal olefin containing from 3 to 20 carbon atoms, and mixtures of such alpha olefin and internal olefin starting materials. In some embodiments, the olefins include vinyl silanes and vinyl siloxanes.

[0141] Solvents are advantageously employed in the hydroformylation process. Any suitable solvent that does not unduly interfere with the hydroformylation process can be used. For example, suitable solvents for rhodium-catalyzed hydroformylation methods include those disclosed, for example, in U.S. Patent Nos. 3,527,809, 4,148,830, 5,312,996, and 5,929,289. Non-limiting examples of suitable solvents include saturated hydrocarbons (alkanes), aromatic hydrocarbons, ethers, aldehydes, ketones, nitriles, alcohols, esters, and aldehyde condensation products. Specific examples of solvents include: tetraethylene glycol dimethyl ether (tetraglyme), pentane, cyclohexane, heptane, benzene, xylene, toluene, diethyl ether, tetrahydrofuran, butyraldehyde, and benzonitrile. Organic solvents can also contain dissolved water up to the saturation limit. Illustrative preferred solvents include ketones (e.g., acetone and methyl ethyl ketone), esters (e.g., ethyl acetate, di-2-ethylhexyl phthalate, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate), hydrocarbons (e.g., toluene), nitrohydrocarbons (e.g., nitrobenzene), ethers (e.g., tetrahydrofuran (THF)), and sulfolane. In a rhodium-catalyzed hydroformylation method, it may be preferred to use an aldehyde compound corresponding to the desired aldehyde product and / or a higher-boiling aldehyde liquid condensation by-product as the main solvent, as described, for example, in U.S. Patent Nos. 4,148,830 and 4,247,486, which may be generated in situ in the hydroformylation method. Due to the nature of the continuous process, the main solvent will typically ultimately contain the aldehyde product and the higher-boiling aldehyde liquid condensation by-product ("heavies"). The amount of the solvent is not particularly critical, and it is only necessary to provide the reaction medium with the required amount of transition metal concentration. Generally, based on the total weight of the reaction fluid, the amount of the solvent ranges from about 5 wt% to about 95 wt%. Mixtures of solvents can be employed.

[0142] The catalyst used in the method of the present invention comprises a transition metal and a polyphosphine ligand. In certain particularly useful embodiments, the catalyst comprises rhodium and a polyphosphine ligand. The most desirable catalysts are free of metal-bound halogens such as chlorine and contain hydrogen, carbon monoxide, and a polyphosphine ligand complexed with a transition metal (preferably rhodium) to produce a catalyst soluble in the liquid phase and stable under the reaction conditions. The transition metal may include Group 8, 9, and 10 metals selected from rhodium (Rh), cobalt (Co), iridium (Ir), ruthenium (Ru), iron (Fe), nickel (Ni), palladium (Pd), platinum (Pt), osmium (Os), and mixtures thereof, wherein the preferred metals are rhodium, cobalt, iridium, and ruthenium, more preferably rhodium, cobalt, and ruthenium, and especially rhodium. The number of available coordination sites on such metals is well known in the art, but the exact coordination mode of the polyphosphine and optionally the monophosphine is unknown. Thus, the catalytic species, which may comprise a complex catalyst mixture, may comprise monomers, dimers, or higher nuclear forms, preferably characterized in that each metal molecule (e.g., rhodium) is complexed with at least one organophosphine molecule. For example, considering the carbon monoxide and hydrogen employed in the hydroformylation reaction, in addition to the organophosphine ligand, the catalytic species of the preferred catalyst employed in the hydroformylation reaction is thought to be complexed with carbon monoxide and hydrogen. In certain preferred embodiments, the transition metal is rhodium. Rhodium may be introduced into the liquid phase as a preformed catalyst, e.g., a stable crystalline solid, hydridocarbonyl-tris(triphenylphosphine)rhodium, RhH(CO)(PPh3)3, which conveniently introduces one equivalent of triarylphosphine. Rhodium may also be introduced into the liquid bulk as a precursor form that is converted in situ to the catalyst. Examples of such precursor forms are rhodium acetylacetonate carbonyltriphenylphosphine, Rh2O3, Rh4(CO) 12 , Rh6(CO) 16 and rhodium acetylacetonate dicarbonyl. Two catalyst compounds that will provide the active species in the reaction medium and their preparation are known in the art, see Brown et al., Journal of the Chemical Society, 1970, pp. 2753-2764.

[0143] Generally, the optimum catalyst concentration depends on the concentration of the α-olefin such as propylene. For example, the higher the propylene concentration, the lower the catalyst concentration typically required to achieve a given conversion of the aldehyde product in a reactor of a given size. Recognizing that partial pressure and concentration are related, using a higher propylene partial pressure results in an increased proportion of propylene in the "off-gas" from the liquid bulk. Since it may be necessary to purge a portion of the gas stream from the product recovery zone to remove a portion of the propane or other inert gases that may be present before recycling to the liquid bulk, the higher the propylene content of the "off-gas", the more propylene will be lost in the propane purge stream. Thus, it is necessary to balance the economic value of the propylene lost in the propane purge stream with the capital savings associated with a lower catalyst concentration.

[0144] The rhodium complex catalyst is preferably in homogeneous form. For example, preformed rhodium hydrido-carbonyl-phosphine ligand catalysts can be prepared and introduced into the hydroformylation reaction mixture. Preferably, the rhodium-phosphine ligand complex catalyst can be derived from a rhodium catalyst precursor which can be introduced into the reaction medium for in-situ formation of the active catalyst. For example, a rhodium catalyst precursor (such as rhodium acetylacetonate dicarbonyl, Rh2O3, Rh4(CO) 12 , Rh6(CO) 16 , Rh(NO3)3, etc.) can be introduced into the reaction mixture together with a polyphosphine for in-situ formation of the active catalyst. In a preferred embodiment, rhodium acetylacetonate dicarbonyl is used as the rhodium precursor and combined with a polyphosphine in a solvent and introduced into the reactor together with syngas for in-situ formation of the active catalyst. Additional polyphosphine ligands and / or optional triarylphosphines can be added if necessary to achieve and maintain the desired concentration. In any case, carbon monoxide, hydrogen and polyphosphines are ligands capable of complexing with the metal and an active metal ligand catalyst is present in the reaction mixture under the conditions used in the hydroformylation reaction.

[0145] The amount of rhodium complex catalyst present in the reaction fluid is the minimum amount necessary to produce the desired productivity. Generally speaking, for most processes, a rhodium concentration in the range of 50 ppmw to 1200 ppmw based on free metal in the reaction fluid should be sufficient, while a metal of 100 ppmw to 800 ppmw is usually preferably employed and more preferably 150 ppmw to 500 ppmw of rhodium.

[0146] Any means can be used to initiate and establish a uniform concentration profile of the tetraphosphine ligand and total polyphosphorus compounds.

[0147] Thus, the rhodium-ligand complex catalyst in the reaction fluid advantageously comprises rhodium complexed with carbon monoxide and a polyphosphine ligand. In one embodiment, a mixture of rhodium-ligand complexes is employed. For example, the catalyst additionally comprises rhodium complexed with carbon monoxide and a polyphosphine ligand in a chelating and / or non-chelating manner. In a preferred embodiment, the rhodium precursor is Rh(triphenylphosphine)(acetylacetonate)(CO), which introduces at least a portion of the triphenylphosphine into the system.

[0148] As described herein, polyphosphine ligands and polydentate ligand degradation products derived therefrom (and optionally monophosphines) are lost or degraded over time by various mechanisms. For commercial operations, the required concentration must be maintained by periodic or continuous addition. To this end, the concentration of the organophosphorus ligand in the reaction fluid is routinely measured by one or more analytical techniques. Unless otherwise specified herein, when referring to the amount of ligand in a reaction, the ligand concentration is determined by HPLC as described in the examples. The ligand concentration in such analyses is typically reported as weight percentage; thus, it is often convenient to use these units for continuous operation.

[0149] In addition to the rhodium complex catalyst, free triarylphosphine can also be present in the reaction fluid and can also be present in the catalyst composition prior to being fed to the reactor. The importance of free ligands is taught in U.S. Patent No. 3,527,809, GB 1,338,225, and Brown et al. (supra, pages 2759 and 2761). In some embodiments, the hydroformylation process of the present invention can involve 30 moles of free (uncomplexed) triarylphosphine per mole of rhodium in the reaction medium, preferably more than 40 moles of triarylphosphine per mole of rhodium, most preferably more than 50 moles of triarylphosphine per mole of rhodium, up to a maximum of 400 moles of free triarylphosphine per mole of rhodium.

[0150] The tetraphosphine compound that can be used as a ligand in the embodiments of the present invention is a compound of formula III:

[0151]

[0152] where each P is a phosphorus atom, and each of R 1 -R 46 is independently hydrogen, a C1 to C8 alkyl group, an aryl group, an alkaryl group, a haloalkyl group, or a halogen, and where (R 5 and R 6 ), (R 15 and R 16 ), (R 25 and R 26 ), and (R 35 and R 36 ) can be a bond. In a preferred embodiment, each of R 1 -R 46 is hydrogen. Other examples of polyphosphines that can be used in some embodiments are described elsewhere in this specification.

[0153] In some embodiments, mixtures of polyphosphines can be used.

[0154] Hydroformylation processes and their operating conditions are well known. In a typical embodiment, an olefin (e.g., propylene) is hydroformylated in a continuous or semi - continuous manner, where the product is separated in a separation zone and the concentrated catalyst solution is recycled back to one or more reactors. The recycling procedure generally involves continuously or intermittently withdrawing a portion of the liquid reaction medium containing the catalyst and the aldehyde product from the hydroformylation reactor, i.e., the reaction zone, and recovering the aldehyde product therefrom by using a composite membrane, as disclosed in U.S. Patent Nos. 5,430,194 and 5,681,473, or by performing a more conventional and preferred distillation method (i.e., evaporation) in a separate distillation zone at atmospheric, reduced, or elevated pressure, as appropriate, in one or more stages, and recycling the residue containing the non - volatile metal catalyst to the reaction zone, as disclosed in, for example, U.S. Patent No. 5,288,918. Condensation of the volatile materials can be carried out in any conventional manner and separation and further recovery can be effected, for example, by further distillation. If desired, the crude aldehyde product can be further purified and isomer - separated, and any recovered reactants such as the olefinic starting material and syngas can be recycled to the hydroformylation zone (reactor) in any desired manner. The recovered metal catalyst containing the retentate from such membrane separation or the recovered non - volatile metal catalyst containing the residue from such vaporization separation can be recycled to the hydroformylation zone (reactor) in any desired conventional manner.

[0155] A typical hydroformylation reaction fluid using a rhodium - polyphosphine ligand complex contains at least a certain amount of four main components or constituents, namely the aldehyde product, the rhodium - polyphosphine ligand complex catalyst, the free polyphosphine ligand, and a solvent for the catalyst and the free polyphosphine ligand. The hydroformylation reaction mixture composition can and typically will contain additional components, such as components deliberately employed during the hydroformylation process or formed in situ during the method. Examples of such additional components include mono - triarylphosphine (Formula II), unreacted olefin starting material, carbon monoxide and hydrogen, and in - situ formed by - products, ligand degradation compounds, and high - boiling liquid aldehyde condensation by - products, as well as other inert co - solvent - type materials or hydrocarbon additives (if employed).

[0156] The hydroformylation reaction conditions employed can vary. For example, the total pressure of hydrogen, carbon monoxide, and the olefin starting compound in the hydroformylation process can range from 1 kPa to 69,000 kPa. However, generally, it is preferred to operate the process at a total pressure of hydrogen, carbon monoxide, and the olefin starting compound of less than 14,000 kPa and more preferably less than 3,400 kPa. The minimum total pressure is mainly limited by the amount of reactants required to achieve the desired reaction rate. The minimum total pressure is mainly limited by the amount of reactants required to achieve the desired reaction rate. More specifically, the partial pressure of carbon monoxide in the hydroformylation process is preferably from 1 kPa to 6,900 kPa, and more preferably from 21 kPa to 5,500 kPa, while the partial pressure of hydrogen is preferably from 34 kPa to 3,400 kPa, and more preferably from 69 kPa to 2,100 kPa. Generally, the molar ratio of gaseous H2:CO can range from 1:10 to 100:1 or higher, and a more preferred molar ratio is from 1:10 to 10:1.

[0157] Generally, the hydroformylation process can be carried out at any operable reaction temperature. Advantageously, the hydroformylation process is carried out at a reaction temperature of -25 °C to 200 °C, preferably 50 °C to 120 °C.

[0158] The hydroformylation process can be carried out using one or more suitable reactors, such as, for example, a continuous stirred tank reactor (CSTR), a Venturi reactor, or a bubble column reactor. The optimal size and shape of the reactor will depend on the type of reactor used. The reaction zone employed can be a single vessel or can comprise two or more discrete vessels. The separation zone employed can be a single vessel or can include two or more discrete vessels. The reaction zone and the separation zone used herein can be present in the same vessel or different vessels. For example, reactive separation techniques (such as reactive distillation and reactive membrane separation) can occur in the reaction zone.

[0159] If desired, the hydroformylation process can be carried out with recycle of unconsumed starting materials. The reaction can be carried out in a single reaction zone or multiple reaction zones, and can be carried out in series or in parallel. The reaction steps can be affected by gradually adding one starting material to another. Similarly, the reaction steps can be combined by co-feeding the starting materials. The starting materials can be added in series to each or all of the reaction zones. When complete conversion is not desired or achievable, the starting materials can be separated from the product, for example, by distillation, and then recycled back to the reaction zone.

[0160] The hydroformylation process can be carried out in reaction equipment of glass-lined, stainless steel, or similar types. The reaction zone can be equipped with one or more internal and / or external heat exchangers in order to control inappropriate temperature fluctuations or to prevent any possible "runaway" reaction temperature.

[0161] The hydroformylation process of the present invention can be carried out in one or more steps or stages. The exact number of reaction steps or stages will depend on the optimal compromise between capital costs and achieving high catalyst selectivity, activity, service life, and ease of operation, as well as the inherent reactivity of the starting materials under discussion and the stability of the starting materials and the desired reaction products to the reaction conditions. In one embodiment, the hydroformylation method of the present invention can be carried out in a multi-stage reactor, such as described, for example, in U.S. Patent No. 5,728,893. Such multi-stage reactors can be designed to have internal physical barriers that create more than one theoretical reaction stage in each vessel.

[0162] As discussed herein, in the hydroformylation method, ligand loss or degradation will occur over time. In some cases, catalyst deactivation can also be observed. By adding a triarylphosphine (as further described herein) to the reaction zone, catalyst deactivation and / or ligand degradation can be advantageously reduced in a hydroformylation method comprising a polyphosphine ligand. According to some embodiments of the present invention, the triarylphosphine compound that can be added to the reaction zone is a compound of formula II:

[0163]

[0164] wherein P is a phosphorus atom, and each of Y 1 -Y 3 is independently an aryl group or a substituted aryl group. Illustrative examples include, but are not limited to, triphenylphosphine, tris(o-tolyl)phosphine, trinaphthylphosphine, tris(p-methoxyphenyl)phosphine, tris(m-chlorophenyl)phosphine, and the like. Representative preferred triarylphosphines include those described in U.S. Patent Nos. 4,283,562 and 5,741,945 (e.g., columns 10, line 57 to column 13, line 39).

[0165] In some embodiments, a mixture of triarylphosphines can be used.

[0166] In some embodiments, the amount of triarylphosphine that can be added to the reaction zone is at least 40 moles of triarylphosphine per mole of transition metal (rhodium). In some embodiments, the amount of triarylphosphine added to the reaction zone is 30 to 400 moles of triarylphosphine per mole of transition metal (rhodium).

[0167] It is generally preferred to conduct the hydroformylation process in a continuous manner. Continuous hydroformylation processes are well known in the art. The continuous process can be carried out in a single-pass mode, i.e., in which a vaporous mixture containing unreacted olefinic starting material and the evaporated aldehyde product is removed from the liquid reaction mixture, whereby the aldehyde product is recovered and a supplemental olefinic starting material, carbon monoxide, and hydrogen are supplied to the liquid reaction medium for the next single pass without recycling the unreacted olefinic starting material. Such recycling procedures are well known in the art and can involve liquid recycling of the metal-organic phosphorus complex catalyst fluid separated from the desired aldehyde reaction product, as disclosed, for example, in U.S. Patent No. 4,148,830; or gas recycling procedures, as disclosed, for example, in U.S. Patent No. 4,247,486; and combinations of liquid and gas recycling procedures as necessary. The most preferred hydroformylation process includes a continuous liquid catalyst recycling method. Suitable liquid catalyst recycling procedures are disclosed, for example, in U.S. Patent Nos. 4,668,651, 4,774,361, 5,102,505, and 5,110,990.

[0168] In one embodiment, the aldehyde product mixture can be separated from the other components of the crude reaction mixture, wherein the aldehyde mixture is produced by any suitable method, such as, for example, solvent extraction, crystallization, distillation, evaporation, wiped-film evaporation, falling-film evaporation, phase separation, filtration, or any combination thereof. It may be necessary to remove the aldehyde product from the crude reaction mixture because they are formed by using a scavenger, as described in WO 88 / 08835. One method of separating the aldehyde mixture from the other components of the crude reaction mixture is by membrane separation, which is described, for example, in U.S. Patent Nos. 5,430,194 and 5,681,473.

[0169] As indicated above, the desired aldehyde can be recovered from the reaction mixture. For example, the recovery techniques disclosed in U.S. Patent Nos. 4,148,830 and 4,247,486 can be used. For example, in a continuous liquid catalyst recycle process, a portion of the liquid reaction mixture removed from the reaction zone (containing the aldehyde product, catalyst, etc.), i.e., the reaction liquor, can enter a separation zone, such as an evaporator / separator, where the desired aldehyde product can be separated from the liquid reaction fluid by distillation in one or more stages at atmospheric, reduced, or elevated pressure, condensed, and collected in a product receiver, and can be further purified if desired. The remaining liquid reaction mixture containing the unvolatilized catalyst can then be recycled back to the reactor, if desired, and any other volatile substances, such as unreacted olefins, and any hydrogen and carbon monoxide dissolved in the liquid reaction separated from the condensed aldehyde product can be removed, for example, by distillation in any conventional manner.

[0170] More specifically, the distillation and separation of the desired aldehyde product from the reaction fluid containing the metal-organic phosphorus complex catalyst can be carried out at any suitable temperature desired. Generally, it is preferred that such distillation be carried out at a relatively low temperature, such as below 150 °C, and more preferably at a temperature in the range of 50 °C to 140 °C. In one embodiment, such aldehyde distillation is carried out under reduced pressure, for example when dealing with low-boiling aldehydes (e.g., C4 to C6), the total gas pressure is significantly lower than the total gas pressure employed during hydroformylation, or when dealing with high-boiling aldehydes (e.g., C7 or greater), it is carried out under vacuum. For example, it is common practice to subject the liquid reaction product medium removed from the hydroformylation reactor to reduced pressure so as to volatilize a substantial portion of the unreacted gas dissolved in the liquid medium into the distillation zone, such as an evaporator / separator, where the desired aldehyde product is distilled, and the liquid medium now contains a much lower syngas concentration than was present in the reaction medium. Generally, for most purposes, a distillation pressure from vacuum pressure to a total gas pressure of up to 340 kPa should be sufficient.

[0171] In one embodiment, a flowing gas can be used in the separation zone to facilitate aldehyde distillation. Such a stripping gas evaporator is described, for example, in U.S. Patent No. 8,404,903.

[0172] The increased concentrations, high temperatures, and low partial pressures present in the separation zone can have a negative impact on the catalyst in terms of catalyst deactivation and / or increased ligand usage. As described in the following examples, an accelerated test procedure (referred to herein as the closed procedure) was designed to demonstrate the effect of the separation zone on the catalyst in order to evaluate various embodiments.

[0173] Illustrative non-optically active aldehyde products of the hydroformylation process according to embodiments of the present invention will depend on the olefin used as a reactant and include, for example, propionaldehyde, n-butyraldehyde, isobutyraldehyde, n-valeraldehyde, 2-methyl-1-butyraldehyde, hexanal, hydroxyhexanal, 2-methyl-1-heptanal, nonanal, 2-methyl-1-octanal, decanal, adipaldehyde, 2-methylglutaraldehyde, 2-methylhexanedial, 3-hydroxypropionaldehyde, 6-hydroxyhexanal, enals such as 2-pentenal, 3-pentenal, and 4-pentenal, alkyl 5-formylvalerate, 2-methyl-1-nonanal, 2-methyl-1-decanal, 3-propyl-1-undecanal, pentadecanal, 3-propyl-1-hexadecanal, eicosanal, 2-methyl-1-tricosanal, pentacosanal, 2-methyl-1-tetracosanal, nonacosanal, 2-methyl-1-octacosanal, hentriacontanal, and 2-methyl-1-triacontanal, etc.

[0174] In some embodiments where propylene is the olefin undergoing hydroformylation, the product is a mixture of n-butyraldehyde and 2-methylpropanal. As previously mentioned, the ratio of the linear (N) to branched (I) isomers (such as the ratio of n-butyraldehyde to 2-methylpropanal (isobutyraldehyde)) is commonly described as the N:I ratio or N:I.

[0175] In one embodiment, the catalyst comprises rhodium, less than one equivalent of polyphosphine, polyphosphine degradation products, and triphenylphosphine (e.g., 30 to 400 moles of triarylphosphine / mole of rhodium), such that the molar ratio of total polyorganic phosphorus compounds to rhodium is greater than 1.25:1. For example, in a process using a catalyst composed of rhodium and polyphosphine and polyphosphine degradation products, triphenylphosphine can be optionally added to further reduce polyphosphine ligand usage and catalyst deactivation.

[0176] Some embodiments of the invention will now be described in more detail in the following examples. Comparative experiments are not embodiments of the invention.

[0177] General procedure

[0178] A liquid recycle reactor system is employed consisting of two 1-liter stainless steel stirred tank reactors connected in series. Each reactor is equipped with a vertically mounted agitator and a circular tubular injector located near the bottom of the reactor. The injector contains a plurality of holes of sufficient size to provide a desired gas flow into the liquid body. The injector is used to feed olefin and / or syngas into the reactor and can also be used to recycle unreacted gas to each reactor. Each reactor has a silicone oil shell as a means of controlling the reactor temperature. Reactors 1 and 2 are further connected via pipelines to transfer any unreacted gas and pipelines to allow a portion of the liquid solution containing aldehyde product and catalyst to be pumped from reactor 1 to reactor 2. Thus, unreacted olefin in reactor 1 is further hydroformylated in reactor 2. Each reactor also contains a pneumatic level controller for maintaining the desired liquid level. Reactor 2 has an exhaust port for removing unreacted gas.

[0179] A portion of the liquid reaction solution is continuously pumped from reactor 2 into a catalyst separation zone containing at least one evaporator, which consists of a heated vessel under reduced pressure.

[0180] The evaporated aldehyde product is condensed and collected in a product receiver. The liquid effluent flows to a vessel (separator) to allow further separation of volatile and non-volatile components. A pneumatic level controller controls the liquid level of the non-volatile components in the separator, including the catalyst solution to be recycled to reactor 1.

[0181]

[0182] The reactor system is charged with a catalyst solution that contains: (a) rhodium dicarbonyl acetylacetonate (280 ppm rhodium), (b) ligand A (0.30 wt% - 0.68 wt%), (c) triphenylphosphine (6 wt% - 12 wt%), (d) a solvent mixture comprising 15 wt% of UCAR FILMER IBT (2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, a substitute for heavy ends formed from the trimerization of isobutyraldehyde) (available from Dow Chemical Company) and approximately 85% butyraldehyde, and (e) hydrogen and carbon monoxide to achieve a partial pressure of 10 psi - 25 psi. The reactor is then heated to 90 °C under flowing carbon monoxide and hydrogen. The pressures of reactor 1 and reactor 2 are maintained at 232 psig and 142 psig, respectively. A propylene olefin stream (composed of approximately 99.5% propylene) is fed to reactor 1 at a rate of 2.7 gram moles per liter of reactor volume per hour - 3.5 gram moles per liter of reactor volume per hour. The first evaporator operates at 100 psig and 120 °C to 140 °C, and the second evaporator operates at 10 psig and 130 °C to 140 °C (depending on the concentration of heavy ends to be removed).

[0183] The system is operated in continuous mode for a period of time while monitoring the concentrations of ligand A, polydentate ligand degradation products, triphenylphosphine, rhodium, and product aldehydes composed of n-butyraldehyde (N-Bal) and isobutyraldehyde (I-Bal). If needed, a solution of ligand A and / or triphenylphosphine (dissolved in toluene) is added to replenish the levels of these ligands upon consumption. If needed, a rhodium catalyst precursor is also added occasionally. Under normal operating conditions, the feed rate of ligand A is adjusted to maintain the target ligand concentration as described herein. In the table below, the ligand usage rate is g / L / day.

[0184] Comparative experiment A and Example 1 were conducted as described in the general procedure, except that the catalyst solution was obtained from a running TPP hydroformylation system where the solvent consisted of mixed butyraldehyde and naturally occurring heavy ends (instead of UCAR FILMER IBT). The initial TPP concentration was 12%, to which 0.30 wt% of ligand A was added. The performance after an initial "break-in" period is given below.

[0185]

[0186] Example 1 provides an N / I comparable to Comparative experiment A and is conducted with a lower usage of ligand A.

[0187] Comparative experiments B - D were conducted as described in the general procedure. The results are shown below:

[0188] Number of on-stream days Equivalent of ligand A / Rh equivalent Total polyphosphorus compound equivalent / Rh equivalent N / I Comparative Example B 100-150 1.05 2.75 28 Comparative Example C 190-210 1.10 3.30 26 Comparative Example D 225-240 0.15 0.90-1.20 8-16

[0189] Comparative experiment D shows that reducing the concentration of the total polyphosphorus compound to less than 1.25 equivalents relative to rhodium and reducing the concentration of ligand A to less than 0.25 equivalents relative to rhodium does not provide the desired performance (i.e., N / I is reduced to below 10).

[0190] Comparative experiment E was conducted according to the general procedure.

[0191] Example 2: By reducing the ligand A feed rate, comparative experiment E was transformed into Example 2. The results are shown below:

[0192]

[0193] Example 2, in which the molar ratio of ligand A to rhodium is less than 1:1, still provides the desired performance (i.e., N / I is comparable to that of comparative experiment E), but the usage rate of the polyphosphine ligand is reduced by 40%.

[0194] Comparative experiments F and G, and Examples 3 and 4 were conducted according to the general procedure, except that TPP was not added. The results are shown below:

[0195] Number of on-stream days Equivalent of ligand A / Rh equivalent Total polyphosphorus compound equivalent / Rh equivalent N / I Comparative Example F 100-115 1.25 2.75 23 Example 3 120-132 0.75 1.75 25 Comparative Example G 142-160 1.30 3.20 29 Example 4 176-182 0.75 1.60 28

[0196] Examples 3 and 4 show that the compositions of the present invention provide good hydroformylation performance when the polyphosphine ligand:transition metal molar ratio is less than 1:1 and the total polyphosphorus compound to rhodium ratio is higher than 1.25.

[0197] Comparative experiment H and Example 5 were conducted according to the general procedure.

[0198]

[0199] Example 5 shows that reducing the ligand A feed rate after comparative experiment H results in a ligand A to rhodium ratio of less than 1:1, but still provides excellent performance and a lower polyphosphine ligand usage rate.

Claims

1. A composition, the composition comprising or derived from: (a) a polyphosphine ligand having the following structure: where each P is a phosphorus atom, and R 1 -R 20 each of which is independently hydrogen, a C1 to C8 alkyl group, a C1 to C8 alkoxy group, an aryl group, an alkaryl group or a halogen, R 47 and R 48 are independently hydrogen, a C1 to C8 alkyl group or a C1 to C8 substituted alkyl group, n is 0 or 1, m is 2 or higher, and Q is an m+1 valent organic group, where R 5 and R 6 and / or R 15 and R 16 may be a linking group forming a bridging structure; and (b) a polyphosphine degradation product derived from the polyphosphine of formula I, wherein the molar ratio of the polyphosphine degradation product to formula I is at least 0.25:1; and (c) Group 8, 9, and 10 transition metals; and (d) a liquid phase comprising product aldehyde and aldehyde condensation product; and (e) Optional A monophosphine having the following structure: wherein P is a phosphorus atom, and each of Y 1 -Y 3 is independently an aryl group or a substituted aryl group, wherein the total moles of polyphosphorus compound relative to the moles of transition metal is greater than 1.1:1, and the molar ratio of formula I to transition metal is less than 1:

1.

2. A method for reducing or slowing the use of a polyphosphine ligand in a continuous hydroformylation process, the method comprising: (a) contacting an olefin with carbon monoxide, hydrogen, and a catalyst, the catalyst comprising (A) a transition metal; (B) a polyphosphine ligand having the following structure: where each P is a phosphorus atom, and R 1 -R 20 each of which is independently hydrogen, a C1 to C8 alkyl group, an aryl group, an alkaryl group, or a halogen, R 47 and R 48 are independently hydrogen, a C1 to C8 alkyl group, or a C1 to C8 substituted alkyl group, n is 0 or 1, m is 2 or greater, and Q is an m+1 valent organic group, where R 5 and R 6 and / or R 15 and R 16 can be a linking group forming a bridging structure; and (b) a polyphosphine degradation product derived from the polyphosphine ligand of formula I; and c) Optional Triphenylphosphine having the following structure: wherein P is a phosphorus atom, and Y 1 -Y 3 each independently is an aryl group or a substituted aryl group; and the contacting is carried out in one or more reaction zones and under hydroformylation conditions; and wherein the ratio of the total moles of polyphosphine ligand and the polydentate degradation product of the polyphosphine to the moles of transition metal is greater than 1.25:1, and (d) monitoring the content of the polyphosphine ligand and the polydentate degradation product of the polyphosphine ligand; and (e) reducing the feed rate of the polyphosphine ligand such that the total moles of polyphosphorus compound relative to the moles of transition metal is greater than 1.25:1, and the ratio of the polyphosphorus to transition metal is less than 1:

1.

3. The method according to claim 2, wherein the ratio of the polyphosphine ligand to the transition metal is greater than 0.25:

1.

4. The method according to claim 2, wherein the total moles of the polyphosphorus compound relative to the transition metal is greater than 1.5:

1.

5. The method according to any one of claims 2 to 4, wherein the amount of triarylphosphine relative to the moles of the transition metal is between 30 moles and 400 moles.

6. The method according to any one of claims 2 to 4, wherein the polyphosphine ligand is as shown in formula III.

7. The method according to any one of claims 2 to 4, wherein the triarylphosphine is triphenylphosphine.

8. The method according to any one of claims 2 to 4, wherein the triarylphosphine is triphenylphosphine and the polyphosphine ligand is formula IV.

9. The method according to any one of claims 2 to 4, wherein the mixed aldehyde in the crude product produced in the method has an N / I ratio higher than 15.

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