Method for slowing catalyst deactivation and / or slowing use of tetraphosphine ligands during hydroformylation

Abstract

The present invention relates to a method for slowing catalyst deactivation and / or slowing use of tetraphosphine ligands during hydroformylation. In one aspect, a process comprises (a) contacting an olefin with carbon monoxide, hydrogen, and a catalyst comprising (A) a transition metal, (B) a tetraphosphine having the structure described herein, and optionally (C) a monophosphine having the structure described herein, the contacting being performed in one or more reaction zones and under hydroformylation conditions; and (b) adding an additional monophosphine having the structure described herein to the reaction zone.

Description

[0001] This application is a divisional application of a Chinese patent application with application number 201980029924.5, filing date May 3, 2019, and invention title "Method for Slowing Catalyst Deactivation and / or Slowing the Use of Tetraphosphine Ligands in the Hydroformylation Process". Technical Field

[0002] The present invention relates to a method for slowing catalyst deactivation and / or slowing the use of tetraphosphine ligands in the hydroformylation process. Background Art

[0003] It is known in the art that aldehydes can be readily prepared by reacting an olefinically unsaturated compound with carbon monoxide and hydrogen in the presence of a dissolved rhodium-triorganophosphine ligand complex catalyst, and a preferred type of such process involves continuous hydroformylation. For example, U.S. Patent No. 3,527,809 discloses the hydroformylation of α-olefins to produce aldehydes at low temperature and low pressure. The process employs certain rhodium complex compounds to effectively catalyze the hydroformylation of olefins with hydrogen and carbon monoxide under a defined set of variables in the presence of a selected triorganophosphine ligand.

[0004] Among the catalysts described in U.S. Patent No. 3,527,809 are compounds containing rhodium and a triarylphosphine ligand (especially a triarylphosphine ligand exemplified by triphenylphosphine ("TPP")). Commercial hydroformylation processes have successfully used 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 - 12 wt% based on the total mass of the reaction fluid. Such high concentrations of TPP are used to obtain the desired product regioselectivity and to increase catalyst stability.

[0005] Over time, hydroformylation catalysts tend to deactivate due to multiple 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 ultimately 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 feeds. The costs associated with PMR, replacing the entire rhodium and ligand inventory, and production losses during catalyst replacement can be significant.

[0006] 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). It is well known that catalysts capable of producing an N:I of greater than about 10-12 are composed of chelating ligands containing at least two phosphorus moieties (see, for example, "Rhodium Catalyzed Hydroformylation", Kluwer Academic Publishers, 2000). Specific examples include, but are not limited to, tetraphosphine ligands such as those described in U.S. Patent No. 7,531,698.

[0007] Such chelating ligands are typically prepared by custom synthesis, which increases their cost. Chelating ligands are known to degrade during continuous operation due to oxidation, hydrolysis, or rhodium-promoted side reactions. Since the hydroformylation rate and product regioselectivity will be challenged if the chelating ligand concentration drops too low, it is common practice to periodically 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 in the method using these expensive compounds.

[0008] There is a desire for a method of slowing catalyst deactivation and / or the ligand usage rate in a high N:I hydroformylation process. Summary of the Invention

[0009] The present invention relates to slowing catalyst deactivation and / or the ligand usage rate of a tetraphosphine ligand in a hydroformylation process. For example, according to some embodiments, it has surprisingly been found that adding certain monophosphines to the reaction zone can slow the decline in the hydroformylation rate and / or slow the ligand usage rate of the chelating tetraphosphine ligand.

[0010] In one aspect, a method for slowing catalyst deactivation and / or slowing the ligand usage of a tetraphosphine ligand in a hydroformylation process comprises:

[0011] (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:

[0012]

[0013] where each P is a phosphorus atom, and each of R 1 -R 46 is independently hydrogen, a C1 to C8 alkyl, aryl, alkaryl, or halogen, and optionally (C) a monophosphine having the following structure:

[0014]

[0015] Wherein P is a phosphorus atom, and Y 1 -Y 3 each independently is aryl, alkaryl, cycloalkyl, benzyl, C3 to C8 alkyl, an alkoxy group having 1 - 8 carbon atoms, aryloxy, or halogen, and the contacting is carried out in one or more reaction zones and under hydroformylation conditions; and

[0016] (b) adding additional monophosphine having the above structure to the reaction zone. In some embodiments, the transition metal is rhodium and the monophosphine is triphenylphosphine.

[0017] These and other embodiments are discussed in more detail in the following detailed description. Detailed Description

[0018] All references to the Periodic Table and the various groups therein refer to the version disclosed in the CRC Handbook of Chemistry and Physics, 72nd Edition (1991 - 1992), CRC Press, pages I - 11.

[0019] Unless stated to the contrary or implied from the context, all parts and percentages are by weight and all test methods are current as of the filing date of this application. For the purposes of U.S. patent practice, the content of any patent, patent application, or publication referenced is incorporated by reference in its entirety (or its equivalent U.S. version is so incorporated by reference), particularly with respect to the disclosure of definitions (to the extent inconsistent with any definitions specifically provided in this invention) and common general knowledge in the art.

[0020] As used herein, "a / an", "the", "at least one", and "one or more" are used interchangeably. The terms "comprising", "including", and variations thereof do not have a limiting meaning when these terms appear in the specification and claims.

[0021] In addition, in this text, the recitation of a numerical range by endpoints includes all the numerical values included within that range (for example, 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.). For the purposes of the present invention, it should be understood that, consistent with what a person of ordinary skill in the art would understand, a numerical range is intended to include and support all possible sub-ranges included within that range. For example, the range 1 to 100 is intended to express 1.01 to 100, 1 to 99.99, 1.01 to 99.99, 40 to 60, 1 to 55, etc. In addition, in this text, the recitation of a numerical range and / or numerical values (including such recitations in the claims) may be interpreted to include the term "about". In such cases, the term "about" refers to a numerical range and / or numerical value that is substantially the same as the numerical range and / or numerical value recited herein.

[0022] As used herein, the term "ppmw" means parts per million by weight.

[0023] For the purposes of the present invention, it is contemplated that the term "hydrocarbon" includes all admissible compounds having at least one hydrogen atom and one carbon atom. Such admissible compounds may also have one or more heteroatoms. In a broad aspect, admissible hydrocarbons include unsubstituted and substituted acyclic (with or without heteroatoms) and cyclic, branched and unbranched, carbocyclic and heterocyclic, aromatic and non-aromatic organic compounds.

[0024] As used herein, unless otherwise indicated, it is contemplated that the term "substituted" includes all admissible substituents of an organic compound. In a broad aspect, admissible substituents include acyclic and cyclic, branched and unbranched, carbocyclic and heterocyclic, aromatic and non-aromatic substituents of an organic compound. Illustrative substituents include, for example, alkyl, alkoxy, aryl, aryloxy, hydroxyalkyl, aminoalkyl (where the number of carbons may range from 1 to 20 or greater, preferably 1 to 12), as well as hydroxy, halo, and amino. For a suitable organic compound, the admissible substituents may be one or more and the same or different. The present invention is not intended to be limited in any way by the admissible substituents of an organic compound.

[0025] As used herein, it is contemplated that the term "hydroformylation" includes (but is not limited to) all hydroformylation processes that involve converting one or more substituted or unsubstituted olefin compounds or a reaction mixture containing one or more substituted or unsubstituted olefin compounds into one or more substituted or unsubstituted aldehydes or a reaction mixture containing one or more substituted or unsubstituted aldehydes. The aldehydes may be asymmetric or non-asymmetric.

[0026] The terms "ligand degradation" and "ligand decomposition" are used interchangeably and are contemplated to include the chemical transformation of a monophosphine or tetraphosphine added to the reaction fluid.

[0027] The term "tetraphosphine ligand usage" is expected to include the amount of tetraphosphine consumed over time in the hydroformylation process (e.g., due to ligand degradation). For example, considering the tetraphosphine added to the hydroformylation process and regularly measuring the tetraphosphine concentration in the reaction fluid (using the HPLC method described in the examples below) will allow calculation of the amount of tetraphosphine consumed by the process.

[0028] The terms "deactivation" and "catalyst deactivation" are used interchangeably and are expected to include the decrease in hydroformylation rate over time. Those of ordinary skill in the art will understand that the hydroformylation rate can be determined using various techniques. As an example, the hydroformylation rate can be determined by making at least two measurements over a period of time under comparable process conditions (e.g., similar rhodium concentration, reaction temperature, gas partial pressure, etc.). For example, the aldehyde production rate is regularly measured over a period of several 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 indicates catalyst deactivation.

[0029] The terms "reaction fluid", "reaction medium", and "catalyst solution" are used interchangeably herein and can include, but are not limited to, a mixture containing: (a) a transition metal-monophosphine complex catalyst (e.g., a rhodium-triphenylphosphine complex catalyst), (b) a transition metal-tetraphosphine complex catalyst (e.g., a rhodium-tetraphosphine complex catalyst), (c) free monophosphine (e.g., triphenylphosphine), (d) free tetraphosphine, (e) an aldehyde product formed in the reaction, (f) unreacted reactants, (g) a solvent for the transition metal complex catalyst and the free phosphine ligand, and optionally (h) degradation products of the monophosphine ligand and the tetraphosphine ligand. The reaction fluid can cover, but is not limited to, (a) the fluid in the reaction zone, (b) the fluid stream flowing 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.

[0030] The term "ligand degradation product" is expected to include, but is not limited to, any and all compounds produced by one or more chemical transformations of at least one tetraphosphine and / or monophosphine molecule added to the reaction fluid. Such compounds can include, but are not limited to, triphosphine or diphosphine compounds resulting from rhodium-promoted cleavage of the parent tetraphosphine and smaller phosphine moieties produced by said cleavage side reactions. It is also expected that ligand degradation products include alkyldiarylphosphines known to be present in rhodium-triarylphosphine hydroformylation catalyst solutions (see, for example, U.S. Patent No. 4,297,239, column 5). Additionally, ligand degradation products are expected to include any and all compounds produced by oxidation of the phosphine moieties. For example, ligand degradation products can include phosphine oxides derived from monophosphines introduced into the process, partially or fully oxidized phosphine oxides derived from tetraphosphines introduced into the process, or phosphine oxides resulting from oxidation of phosphine compounds produced by rhodium-promoted side reactions (such as oxidation of triphosphine compounds derived from the parent tetraphosphine).

[0031] As used herein, the terms "tetradentate phosphine" and "tetraphosphine" are used interchangeably and are expected to include compounds containing four phosphorus atoms, each phosphorus atom bonded to three carbon atoms.

[0032] As used herein, the terms "monodentate phosphine" and "monophosphine" are used interchangeably and include compounds containing a single phosphorus atom bonded to three carbon atoms.

[0033] 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, wherein ligands are bound or coordinated via electronic interactions. Examples of such ligands include, but are not limited to, monophosphines, tetradentate phosphines, carbon monoxide, propylene, and hydrogen.

[0034] As used herein, the term "free" phosphine is expected to include monophosphine or tetraphosphine molecules that are not bound or coordinated to rhodium.

[0035] Generally, the present invention is directed to methods for slowing catalyst deactivation and / or slowing the use of tetraphosphine ligands during the hydroformylation process. The catalyst comprises a transition metal (such as rhodium) and a tetraphosphine ligand.

[0036] In one aspect, a method for slowing catalyst deactivation and / or slowing the use of tetraphosphine ligands during the hydroformylation process comprises:

[0037] (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:

[0038]

[0039] wherein each P is a phosphorus atom, and R 1 -R 46Each of them is independently hydrogen, a C1-C8 alkyl group, an aryl group, an alkaryl group, or a halogen, and optionally (C) a monophosphine having the following structure:

[0040]

[0041] wherein P is a phosphorus atom, and Y 1 -Y 3 Each of them is independently an aryl group, an alkaryl group, a cycloalkyl group, a benzyl group, a C3-C8 alkyl group, an alkoxy group having 1-8 carbon atoms, an aryloxy group, or a halogen, and the contacting is carried out in one or more reaction zones and under hydroformylation conditions; and

[0042] (b) adding an additional monophosphine having the above structure to the reaction zone. In some embodiments, the transition metal includes rhodium. In some embodiments, the olefin is propylene. In some embodiments, the amount of monophosphine added is at least 40 moles of phosphine per mole of transition metal. In some embodiments, based on the total weight of the reaction fluid in the reaction zone, the amount of monophosphine added to the reactor zone is greater than 1.5 wt% of the reaction fluid in the reaction zone.

[0043] In some embodiments, the monophosphine is one or more of the following: triphenylphosphine, tris(o-tolyl)phosphine, tris(naphthyl)phosphine, tris(p-methoxyphenyl)phosphine, tris(m-chlorophenyl)phosphine, tribenzylphosphine, tricyclohexylphosphine, dicyclohexylphenylphosphine, cyclohexyldiphenylphosphine, and trioctylphosphine. In some embodiments, the monophosphine is triphenylphosphine. In some embodiments, the monophosphine is a bulky monophosphine. In some embodiments, the catalyst includes a mixture of monophosphines of different species.

[0044] In some embodiments, each R in the structure of the tetraphosphine 1 -R 46 is hydrogen. In some embodiments, the catalyst includes one or more of the following tetraphosphines:

[0045]

[0046]

[0047] In some embodiments, the transition metal includes rhodium, the monophosphine is triphenylphosphine, each R 1 -R 46 is hydrogen, and the olefin includes propylene.

[0048] In some embodiments, the decrease in the hydroformylation rate over time is less than the decrease in the hydroformylation rate over time in a method in the absence of monophosphine under the same conditions. In some embodiments, the rate of use of the tetraphosphine ligand in the hydroformylation process is lower than the rate of use of the tetraphosphine ligand in the hydroformylation process in the absence of monophosphine under the same conditions.

[0049] Hydrogen and carbon monoxide can be obtained from any suitable source, including petroleum cracking and refinery operations.

[0050] Synthesis gas (from synthesis gas) is the name given to a gas mixture containing variable amounts of CO and H2. The production methods are well known. Hydrogen and CO are usually the main components of synthesis gas, but synthesis gas 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 is preferably between 1:10 and 10:1. Synthesis gas is commercially available and is usually used as a fuel source or as an intermediate for producing other chemicals. For most hydroformylation applications, the most preferred H2:CO molar ratio in chemical production is between 3:1 and 1:3, and usually targets between about 1:2 and 2:1. The synthesis gas mixture is a preferred source of hydrogen and CO.

[0051] The olefin starting material reactants that can be used in the hydroformylation reactions covered by the present invention can be terminal or internal unsaturated and have a straight-chain, branched-chain or cyclic structure. Such olefins can contain 2 to 20 carbon atoms and can contain one or more ethylenically unsaturated groups. In addition, such olefins can contain groups or substituents that will not substantially and adversely interfere with the hydroformylation process, such as carbonyl, carbonyloxy, oxy, hydroxy, oxycarbonyl, halogen, alkoxy, aryl, alkyl, haloalkyl, etc. Exemplary olefinically unsaturated compounds include alpha olefins, internal olefins, alkyl esters of olefinic acids, alkenyl esters of alkanoic acids, 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, etc. Of course, it should be understood that mixtures of different olefin starting materials can be used when necessary. The examples of the present invention can be particularly used for the hydroformylation of C3 and higher carbon olefins. Thus, in some embodiments, the olefinically unsaturated starting material is an alpha olefin containing 3 to 20 carbon atoms, an internal olefin containing 3 to 20 carbon atoms, and mixtures of such alpha olefins and internal olefins as starting materials.

[0052] Advantageously, a solvent is used in the hydroformylation process. Any suitable solvent that does not unduly interfere with the hydroformylation process can be used. By way of illustration, suitable solvents for rhodium-catalyzed hydroformylation processes include those disclosed in, for example, U.S. Patents 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, pentane, cyclohexane, heptane, benzene, xylene, toluene, diethyl ether, tetrahydrofuran, butyraldehyde, and benzonitrile. The organic solvent may also contain water in solution 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 the rhodium-catalyzed hydroformylation process, it may be preferred to employ an aldehyde compound corresponding to the aldehyde product to be prepared and / or a higher-boiling aldehyde liquid condensation by-product (e.g., as may be formed in situ during a hydroformylation process as described in, for example, US 4,148,830 and US 4,247,486) as the main solvent. Due to the nature of the continuous process, the main solvent will typically ultimately include the aldehyde product and the higher-boiling aldehyde liquid condensation by-products ("heavy materials"). The amount of solvent is not particularly critical and only needs to be sufficient to provide the desired concentration of transition metal in the reaction medium. Generally, the amount of solvent ranges from about 5 wt% to about 95 wt% based on the total weight of the reaction fluid. Mixtures of solvents can be used.

[0053] The catalyst for use in the method of the present invention comprises a transition metal and a tetraphosphine. In certain particularly useful embodiments, the catalyst comprises rhodium and a tetraphosphine. Most desirably, the catalyst is free of metal-bound halogens (e.g., chlorine) and contains hydrogen, carbon monoxide, and a tetraphosphine that complexes with the rhodium metal to produce a catalyst that is soluble in the above-described liquid phase and stable under the reaction conditions.

[0054] The transition metal may comprise 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, where the preferred metals are rhodium, cobalt, iridium, and ruthenium, more preferably rhodium, cobalt, and ruthenium, and particularly rhodium.

[0055] The number of available coordination sites on such metals is well known in the art. Thus, catalytic substances which may comprise a complex catalyst mixture may comprise monomers, dimers or higher nuclear forms, which are preferably characterized by at least one molecule containing an organophosphine complexed to each metal (e.g. rhodium) molecule. For example, in view of the hydroformylation reaction using carbon monoxide and hydrogen, it is believed that the catalytic species of the preferred catalyst used in the hydroformylation reaction may complex with carbon monoxide and hydrogen in addition to the organophosphine ligand.

[0056] In certain preferred embodiments, the transition metal is rhodium. Rhodium may be introduced into the liquid phase as a preformed catalyst, such as a stable crystalline solid, rhodium hydrido-carbonyl-tris(triphenylphosphine), RhH(CO)(PPh3)3. Rhodium may be introduced into the liquid in precursor form, which is converted in situ to the catalyst. Examples of such precursor forms are rhodium carbonyltriphenylphosphine acetylacetonate, Rh2O3, Rh4(CO) 12 、Rh6(CO) 16 and rhodium dicarbonyl acetylacetonate. The catalyst compounds which 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.

[0057] Generally, the optimal 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 generally required to achieve a given conversion to the aldehyde product in a reactor of a given size. Recognizing that partial pressure is related to concentration, using a higher propylene partial pressure results in an increased proportion of propylene in the "off-gas" from the liquid. Since it may be necessary to purify a portion of the gas stream from the product recovery zone to remove a portion of the propane that may be present before recycling to the liquid, the higher the propylene content of the "off-gas", the more propylene will be lost in the propane purification stream. Therefore, it is necessary to balance the economic value of the propylene lost in the propane purification stream against the capital savings associated with a lower catalyst concentration.

[0058] The rhodium complex catalyst may be in homogeneous or heterogeneous form. For example, a preformed rhodium hydrido-carbonyl-phosphine ligand catalyst may be prepared and introduced into the hydroformylation reaction mixture. More preferably, the rhodium-phosphine ligand complex catalyst may be derived from a rhodium catalyst precursor which may be introduced into the reaction medium for in situ formation of the active catalyst. For example, rhodium catalyst precursors such as rhodium dicarbonyl acetylacetonate, Rh2O3, Rh4(CO) 12 、Rh6(CO) 16, Rh(NO3)3, etc., can be introduced into the reaction mixture together with the tetraphosphine for in-situ formation of the active catalyst. In a preferred embodiment, rhodium acetylacetonate dicarbonyl is used as the rhodium precursor and combined with the tetraphosphine in a solvent and introduced into the reactor together with syngas for in-situ formation of the active catalyst. Additional tetraphosphine can be added as needed to achieve and maintain the desired concentration. In any case, for the purposes of the present invention, carbon monoxide, hydrogen, and the tetraphosphine are all ligands capable of complexing with the metal, and it is sufficient for the active metal ligand catalyst to be present in the reaction mixture under the conditions for the hydroformylation reaction.

[0059] In some embodiments, the catalyst composition is formed in a mixing tank by combining the rhodium catalyst precursor with the tetraphosphine.

[0060] The amount of the rhodium complex catalyst present in the reaction fluid only needs to be the minimum amount required to achieve the desired productivity. Generally, a rhodium concentration in the range of 150 ppmw to 1200 ppmw based on the free metal in the reaction fluid in the hydroformylation reactor should be sufficient for most processes, while a metal concentration of 150 ppmw to 800 ppmw is generally preferred, and a rhodium concentration of 150 ppmw to 500 ppmw is more preferred.

[0061] The amount of the tetraphosphine in the catalyst composition (whether formed entirely in the mixing tank or in the reactor) is at least 1 mole of tetraphosphine per mole of transition metal (rhodium). In some embodiments, the amount of the tetraphosphine in the catalyst composition (whether formed entirely in the mixing tank or in the reactor) is 1 to 10 moles of tetraphosphine per mole of transition metal (rhodium). As described in the examples, the molar amount of the tetraphosphine is measured by high performance liquid chromatography (HPLC). The molar amount of rhodium is measured by atomic absorption.

[0062] For commercial operation, the ligand concentration must be maintained by periodic or continuous addition. To this end, the ligand concentration in the reaction fluid is routinely measured by one or more analytical techniques; high performance liquid chromatography (HPLC) is generally preferred. Unless otherwise specified herein, when referring to the amount of the ligand in the reaction, the ligand concentration is determined by HPLC as described in the examples. The ligand concentration in such analyses is usually reported as a weight percentage; therefore, it is usually convenient to use these units for continuous operation. In some embodiments, the amount of the tetraphosphine in the reaction fluid in the reactor of the hydroformylation process is greater than or equal to 0.06 wt% based on the total weight of the reaction fluid in the reactor. In some embodiments, the amount of the tetraphosphine in the reaction fluid in the reactor of the hydroformylation process is 0.1 to 9 wt% based on the total weight of the reaction fluid in the reactor. In which the R in the tetraphosphine shown above 1 -R 46In some embodiments where each is hydrogen, the amount of the tetraphosphine in the reaction fluid in the reactor of the hydroformylation process is from 0.1 to 4% by weight based on the total weight of the reaction fluid in the reactor.

[0063] By way of illustration, a preferred catalyst precursor composition consists essentially of a dissolved rhodium complex precursor, a tetraphosphine, and a solvent. As evidenced by the evolution of carbon monoxide gas, the tetraphosphine will readily displace at least one of the carbonyl ligands of the rhodium acetylacetonate complex precursor. After introducing the catalyst precursor composition into the reactor, additional tetraphosphine may then optionally be added to achieve the target concentration in the reaction fluid.

[0064] Thus, the rhodium-ligand complex catalyst in the reaction fluid of the hydroformylation reactor advantageously comprises rhodium complexed with carbon monoxide and a tetraphosphine. In one embodiment, a mixture of rhodium-ligand complexes is used. By way of example, the catalyst further comprises rhodium complexed with carbon monoxide and a tetraphosphine in a chelating and / or non-chelating manner.

[0065] In addition to the rhodium complex catalyst, free monophosphine (i.e., monophosphine not complexed with a metal) may also be present in the reaction fluid and may also be present in the catalyst composition before being fed to the reactor, depending on the particular components. The importance of free ligands is taught in US 3,527,809, GB 1,338,225, and Brown et al., supra, at pages 2759 and 2761. In some embodiments, the hydroformylation process of the present invention may involve 1% by weight or more of free monophosphine in the reaction medium. The reaction fluid may also contain free tetradentate phosphine. In some such embodiments, the concentration of free tetradentate phosphine may range from 0.1 to 10 moles per mole of rhodium.

[0066] The tetraphosphine compound that can be used as a ligand in the embodiments of the present invention is a compound of formula I:

[0067]

[0068] where each P is a phosphorus atom, and R 1 -R 46 each of which is independently hydrogen, a C1 to C8 alkyl group, an aryl group, an alkaryl group, a haloalkyl group, or a halogen. In a preferred embodiment, each of R 1 -R 46 is hydrogen. Other examples of tetraphosphines that can be used in some embodiments are described elsewhere in this specification.

[0069] Mixtures of tetraphosphines can be used in some embodiments.

[0070] 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, for example, the composite membranes disclosed in US 5,430,194 and US 5,681,473 or by the more conventional and preferred method of distilling it (i.e., vaporizing and separating) in a separate distillation zone at atmospheric, reduced, or elevated pressure as needed in one or more stages. The non - volatile residue containing the metal catalyst, such as that disclosed in US 5,288,918, is recycled back to the reaction zone. The condensation of the volatile materials and their separation and further recovery (e.g., by further distillation) can be carried out in any conventional manner. If necessary, the crude aldehyde product can be passed on for further purification and isomer separation, and any recovered reactants (e.g., olefin starting material and syngas) can be recycled back to the hydroformylation zone (reactor) in any desired manner. The raffinate containing the metal catalyst recovered by such membrane separation or the residue containing the non - volatile metal catalyst recovered by such vaporization separation can be recycled back to the hydroformylation zone (reactor) in any desired conventional manner.

[0071] A typical hydroformylation reaction fluid using a rhodium - tetraphosphine ligand complex contains at least some amounts of four main components or constituents, namely the aldehyde product, the rhodium - tetraphosphine ligand complex catalyst, the free tetraphosphine ligand, and the solvent for the catalyst and the free ligand. The hydroformylation reaction mixture composition can and usually will contain additional components, such as those that have been deliberately employed in the hydroformylation process or those that are formed in situ during the process. Examples of such additional components include unreacted olefin starting materials, carbon monoxide and hydrogen, as well as by - products formed in situ, ligand degradation compounds, high - boiling liquid aldehyde condensation by - products, and other inert co - solvent type materials or hydrocarbon additives (if used).

[0072] The hydroformylation reaction conditions used can vary. For example, the total pressure of hydrogen, carbon monoxide, and the olefin starting compound in the hydroformylation process can range from 1 to 69,000 kPa. However, generally, the process is preferably operated 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. More specifically, the partial pressure of carbon monoxide in the hydroformylation process is preferably from 1 to 6,900 kPa and more preferably from 21 to 5,500 kPa, while the partial pressure of hydrogen is preferably from 34 to 3,400 kPa and more preferably from 69 to 2,100 kPa. Generally, the molar ratio of gaseous H2:CO can range from 1:10 to 100:1 or higher, and more preferably the molar ratio is from 1:10 to 10:1.

[0073] 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.

[0074] The hydroformylation process can be carried out using one or more suitable reactors, such as a continuous stirred tank reactor (CSTR), a Venturi reactor, a bubble column reactor, or a slurry reactor. The optimal size and shape of the reactor will depend on the type of reactor used. The reaction zone used can be a single vessel or can comprise two or more discrete vessels. The separation zone used can be a single vessel or can comprise two or more discrete vessels. The reaction zone and the separation zone used herein can be present in the same vessel or in different vessels. For example, reactive separation techniques (such as reactive distillation and reactive membrane separation) can occur in the reaction zone.

[0075] If necessary, the hydroformylation process can be carried out with recycling of unconsumed starting materials. The reaction can be carried out in a single reaction zone or multiple reaction zones, and in series or in parallel. The reaction step can be achieved by incrementally adding one starting material to the other starting materials. In addition, the reaction steps can be combined by jointly adding the starting materials. The starting materials can be added to each or all of the reaction zones in series. When complete conversion is not required or not achievable, the starting materials can be separated from the product, for example, by distillation, and the starting materials are then recycled back to the reaction zone.

[0076] The hydroformylation process can be carried out in a stainless steel or similar type of reaction equipment with a glass lining. The reaction zone can be equipped with one or more internal and / or external heat exchangers to control inappropriate temperature fluctuations or prevent any possible "runaway" reaction temperature.

[0077] 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 be determined by an optimal overall consideration between capital costs and achieving high catalyst selectivity, activity, lifetime, and ease of operation, as well as the inherent reactivity of the relevant starting materials and the stability of the starting materials and the desired reaction products to the reaction conditions.

[0078] In one embodiment, the hydroformylation can be carried out in a multi-stage reactor, such as that described in US 5,728,893. Such multi-stage reactors can be designed with internal physical barriers, with each vessel forming more than one theoretical reaction stage.

[0079] As discussed herein, over time in the hydroformylation process, there is some catalyst deactivation and / or ligand degradation. By adding a monophosphine (as further described herein) to the reaction zone and using a tetraphosphine ligand, catalyst deactivation and / or ligand degradation can be advantageously reduced in such hydroformylation processes.

[0080] The monophosphine compound that can be added to the reaction zone according to an embodiment of the present invention is a compound of formula II:

[0081]

[0082] wherein P is a phosphorus atom, and each of Y 1 -Y 3 is independently an aryl, alkaryl, cycloalkyl, benzyl, C3 to C8 alkyl, alkoxy having 1 - 8 carbons, aryloxy, or halogen. Illustrative examples include, but are not limited to, triphenylphosphine, tris(o-tolyl)phosphine, trinaphthylphosphine, tris(p-methoxyphenyl)phosphine, tris(m-chlorophenyl)-phosphine, tribenzylphosphine, tricyclohexylphosphine, dicyclohexylphenylphosphine, cyclohexyldiphenylphosphine, trioctylphosphine, etc.

[0083] In some embodiments, the monophosphine is a bulky or sterically hindered monophosphine. For the purposes of the present invention, a "bulky" or "sterically hindered" ligand is a ligand having a Tolman cone angle of 135 to 190°. For example, in some such embodiments, each of Y 1 -Y 3 can independently be a substituted or unsubstituted C3 to C8 alkyl, a substituted or unsubstituted C5 to C8 cycloalkyl, or a substituted or unsubstituted C6 to C12 aryl. Representative preferred bulky monophosphines include those described in U.S. 4,283,562 and U.S. Patent No. 5,741,945 (e.g., columns 10, line 57 to column 13, line 39).

[0084] In some embodiments, a mixture of monophosphines can be used.

[0085] In some embodiments, the amount of monophosphine that can be added to the reaction zone is at least 40 moles of monophosphine per mole of transition metal (rhodium). In some embodiments, the amount of monophosphine added to the reaction zone is 40 to 350 moles of monophosphine per mole of transition metal (rhodium).

[0086] Although the tetraphosphine ligand can conceivably degrade into one or more monophosphine compounds, the amount of monophosphine added to the reaction fluid in embodiments according to the invention is far greater than the amount that might be expected to occur via degradation. In other words, the vast majority of the monophosphine added to the reaction fluid (e.g., not derived from the catalyst composition or the tetraphosphine present in the reaction fluid).

[0087] For commercial operations, the ligand concentration must be maintained by periodic or continuous addition. To this end, the ligand concentration in the reaction fluid is routinely measured by one or more analytical techniques; high performance liquid chromatography (HPLC) is generally preferred. Unless otherwise specified herein, when referring to the amount of monophosphine ligand in the reaction zone, the ligand concentration is determined by HPLC as described in the examples. The ligand concentration in such analyses is typically reported as a weight percentage; thus, it is often convenient to use these units for continuous operation. In some embodiments, based on the total weight of the reaction fluid in the reactor, the amount of monophosphine added to the reactor is greater than 1.5 wt% of the reaction fluid in the reactor. In some embodiments, based on the total weight of the reaction fluid in the reactor, the amount of monophosphine added to the reactor is 1.5 to 13 wt% of the reaction fluid in the reactor.

[0088] In some embodiments, adding monophosphine to the hydroformylation reactor using the tetraphosphine of formula (I) (as discussed herein) advantageously reduces the decrease in the hydroformylation rate that is normally expected. That is, when the specified monophosphine is added, the decrease in the hydroformylation rate over time is less than the decrease in the hydroformylation rate over time in a hydroformylation process under the same conditions except for the absence of monophosphine. This can advantageously facilitate the production of more aldehyde over time using the same amount of transition metal / tetraphosphine catalyst.

[0089] In some embodiments, adding monophosphine to the hydroformylation reactor using the tetraphosphine of formula (I) (as discussed herein) advantageously reduces the rate of consumption of the tetraphosphine ligand that is normally expected. That is, when the specified monophosphine is added, the tetraphosphine used as a ligand will degrade at a lower rate than in the same conditions but in the absence of monophosphine. This can advantageously extend the service life of the transition metal / tetraphosphine catalyst.

[0090] The hydroformylation process is generally preferably carried out 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., a vapor mixture comprising unreacted olefin starting material and vaporized aldehyde product is removed from the liquid reaction mixture from which the aldehyde product is recovered and supplementary olefin starting material, carbon monoxide, and hydrogen are supplied to the liquid reaction medium for the next single pass without recycling the unreacted olefin starting material. Recycling procedures of this type are well known in the art and can involve, for example, liquid recycling of a metal-organic phosphorus complex catalyst fluid separated from the desired aldehyde reaction product as disclosed, for example, in U.S. 4,148,830 or gas recycling procedures as disclosed, for example, in U.S. 4,247,486, and combinations of both recycling procedures if necessary. The most preferred hydroformylation process involves a continuous liquid catalyst recycling process. Suitable liquid catalyst recycling procedures are disclosed, for example, in U.S. Patents 4,668,651, 4,774,361, 5,102,505, and 5,110,990.

[0091] In one embodiment, the aldehyde product mixture can be separated from the other components of the crude reaction mixture, where the aldehyde mixture is produced using any suitable method, such as solvent extraction, crystallization, distillation, vaporization, 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 upon its formation via the use of a capturant as described in WO 88 / 08835. One method for separating the aldehyde mixture from the other components of the crude reaction mixture is by using membrane separation, which is described, for example, in U.S. Patents 5,430,194 and 5,681,473.

[0092] As described above, the desired aldehyde can be recovered from the reaction mixture. For example, the recovery techniques disclosed in U.S. Patents 4,148,830 and 4,247,486 can be used. For example, in a continuous liquid catalyst recycling process, a portion of the liquid reaction mixture (containing aldehyde product, catalyst, etc.) (i.e., the reaction fluid) removed from the reaction zone can be transferred to a separation zone (such as a vaporizer / separator), where the desired aldehyde product can be separated from the liquid reaction fluid by distillation, condensed, and collected in a product receiver at atmospheric, reduced, or elevated pressure in one or more stages, and further purified if desired. The remaining non-volatile liquid reaction mixture containing the catalyst can then be recycled back to the reactor, as any other volatile substances (such as unreacted olefins) can be dissolved in the liquid reactants after being separated from the aldehyde product, for example, by distillation and condensation in any conventional manner, along with any hydrogen and carbon monoxide as necessary.

[0093] 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 desired temperature. Generally, such distillation is preferably carried out at a relatively low temperature (e.g., 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, such as a total pressure substantially lower than the total pressure used during hydroformylation, when dealing with low-boiling aldehydes (e.g., C4 to C6), or under vacuum when dealing with high-boiling aldehydes (e.g., C7 or higher). For example, it is conventional to subject the liquid reaction product medium removed from the hydroformylation reactor to reduced pressure so that a substantial portion of the unreacted gas dissolved in the liquid medium and now containing a much lower syngas concentration compared to that present in the reaction medium volatilizes into the distillation zone (e.g., vaporizer / separator) where the desired aldehyde product is distilled. Generally, a distillation pressure in the range of vacuum pressure up to 340 kPa total pressure should be sufficient for most purposes.

[0094] In one embodiment, a flowing gas can be used in the separation zone to facilitate aldehyde distillation. Such a stripping gas vaporizer is described, for example, in US 8404903.

[0095] In terms of catalyst deactivation and / or increased ligand use, the increased concentrations, high temperatures, and low partial pressures that occur in the separation zone can have a negative impact on the catalyst. As described in the examples below, an accelerated test procedure (referred to herein as the closed procedure) has been designed to demonstrate the effect of the separation zone on the catalyst in order to evaluate various embodiments.

[0096] Illustrative non-optically active aldehyde products of the hydroformylation process according to embodiments of the present invention will depend on the olefin used as the reactant and can 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-methyladipaldehyde, 3-hydroxypropionaldehyde, 6-hydroxyhexanal, enals (e.g., 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.

[0097] In some embodiments where propylene is the olefin undergoing the hydroformylation reaction, the product is a mixture of n-butyraldehyde and 2-methylpropanal. As previously mentioned, the ratio of the straight-chain (N) to branched-chain (I) isomers, such as the ratio of n-butyraldehyde to 2-methylpropanal (isobutyraldehyde), is commonly described as the N:I ratio or N:I.

[0098] In one embodiment, the catalyst comprises rhodium, one or more equivalents of a tetraphosphine, and triphenylphosphine (e.g., 1.5 - 12 wt%). For example, in a process utilizing a catalyst composed of rhodium and a tetraphosphine, triphenylphosphine may be optionally added to reduce the use of the tetraphosphine ligand and catalyst deactivation.

[0099] Accordingly, the present invention provides at least the following:

[0100] 1. A method for slowing catalyst deactivation and / or slowing the use of a tetraphosphine ligand in a hydroformylation process, the method comprising:

[0101] (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:

[0102]

[0103] 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, or a halogen, and optionally (C) a monophosphine having the following structure:

[0104]

[0105] where P is a phosphorus atom, and each of Y 1 -Y 3 is independently an aryl group, an alkaryl group, a cycloalkyl group, a benzyl group, a C3 to C8 alkyl group, an alkoxy group having 1 - 8 carbon atoms, an aryloxy group, or a halogen, the contacting being carried out in one or more reaction zones and under hydroformylation conditions; and

[0106] (b) adding an additional monophosphine having the above structure to the reaction zone.

[0107] 2. The method according to claim 1, wherein the monophosphine is triphenylphosphine.

[0108] 3. The method according to claim 1, wherein the monophosphine is a bulky monophosphine.

[0109] 4. The method according to any one of the preceding claims, wherein the transition metal comprises rhodium.

[0110] 5. The method according to any one of the preceding claims, wherein each R 1 -R 46 is hydrogen.

[0111] 6. The method according to any one of the preceding claims, wherein the olefin is propylene.

[0112] 7. The method according to claim 1, wherein the decrease in the hydroformylation rate over time is less than the decrease in the hydroformylation rate in a process under the same conditions but lacking the monophosphine.

[0113] 8. The method according to claim 1, wherein the rate of use of the tetraphosphine ligand in the hydroformylation process is less than the rate of use of the tetraphosphine ligand in a hydroformylation process under the same conditions but lacking the monophosphine.

[0114] 9. The method according to any one of the preceding claims, wherein the amount of monophosphine added is at least 40 moles of phosphine per mole of transition metal.

[0115] 10. The method according to any one of the preceding claims, wherein the amount of monophosphine added to the reactor zone is greater than 1.5% by weight of the reaction fluid in the reaction zone, based on the total weight of the reaction fluid in the reaction zone.

[0116] Some embodiments of the present invention will now be described in more detail in the following examples.

[0117] Examples

[0118] In the following examples, all parts and percentages are by weight unless otherwise specified. The concentration of ligand A is expressed in equivalents as the number of moles of ligand A per mole of rhodium. Unless otherwise stated, the pressures in the following examples are expressed in pounds per square inch gauge. Unless otherwise stated, all operations, such as the preparation of the catalyst solution, are carried out under an inert atmosphere. The comparative experiments are not examples of the present invention.

[0119] The gas composition (mole %) is measured by gas chromatography (GC), and the partial pressures are then calculated based on the total pressure using Raoult's law.

[0120] The free tetradentate phosphine concentration is measured by high-pressure liquid chromatography (HPLC). To prevent oxidation during analysis, the phosphine is derivatized to stable phosphine sulfide by mixing with a diluent saturated with sulfur (50:50 (volume) acetonitrile: THF saturated with elemental sulfur).

[0121] External standard HPLC analysis was performed on an Agilent 1200 Infinity series HPLC equipped with a UHPLC SB-C8 3.0 mm, 1.8 μm guard column, followed by a Zorbax SB-C8 analytical column (3.0 × 150 mm). The solvent gradient was 55% water and the balance acetonitrile for 4 minutes; then adjusted to 20:80 water:acetonitrile for 22 minutes, and finally returned to the original composition for the remaining 35 minutes of operation. The solvent flow rate was always 1.00 mL / min and the column temperature was maintained at 40 °C. Two microliters of the sample was injected into the system; the multi-wavelength UV detector was set at 240 nm.

[0122] Preparation of Ligand A

[0123] The tetradentate phosphine compound ligand A was used in these examples and was prepared as described below.

[0124]

[0125] Synthesis of 1,1'-Biphenyl-2,2',6,6'-tetracarboxylic Acid To a 5 L jacketed reactor equipped with an overhead stirrer, bottom drain valve, and water-cooled condenser was added 1 L of dichloromethane and 50 g (0.247 mol) of pyrene. The mixture was stirred until the pyrene dissolved, then 0.25 L of acetonitrile, 1.5 L of deionized water, and 2.0 g of ruthenium(III) chloride were added. The resulting two-phase mixture was stirred vigorously and cooled to 18 °C by circulating the cooling fluid through the jacket. Then, small portions of sodium periodate (total 500 g; 2.34 mol) were added over a 2.5-hour period while maintaining the reactor temperature at 23 - 27 °C. The reaction mixture, which was initially brown, quickly turned dark brown and finally became brown-green. After stirring overnight (18 hours), stirring was stopped and the layers were separated. The lower layer was drained into a Buchner funnel to collect the green / brown crude solid product, which was washed with dichloromethane (2 × 500 mL), and dried on the filter with flowing air. The solid was then returned to the reactor and refluxed with 1.5 L of acetone for 1 hour. After cooling to room temperature, the yellow solution was drained into a Buchner funnel, and the filtrate was concentrated on a rotary evaporator to give a yellow solid. The crude tetraacid product was dried in a vacuum oven at 70 °C overnight and used without further purification.

[0126]

[0127] Synthesis of 1,1'-Biphenyl-2,2',6,6'-tetramethanol.Dry the 5 L reactor used in the previous step and purge it with nitrogen overnight. Under nitrogen, add crude 1,1'-biphenyl-2,2',6,6'-tetracarboxylic acid (50.0 g, 0.152 mol) and 1.5 L of THF. Stir the resulting solution and cool it to 0 °C by circulating the cooled fluid through the jacket of the reactor. Then add a solution of lithium aluminum hydride in THF (1 M; 666 mL; 0.665 mol) via a peristaltic pump over 2 hours. During this period, stir the mixture vigorously and maintain the reactor temperature at 0 - 2 °C; for safety purposes, apply a slow nitrogen purge to the reactor and pass the effluent stream through a condenser to scavenge the hydrogen evolved from the reactor. After the addition of lithium aluminum hydride is complete, stir and cool the reactor for an additional 15 minutes, then allow it to warm slowly to room temperature. After stirring at room temperature for 30 minutes, heat the reactor contents to 65 °C and stir overnight under a slow nitrogen purge. The next morning, cool the reactor to 0 °C and quench it with 25 mL of water added slowly via a peristaltic pump over a 1.5-hour period at 0 - 7 °C, then 50 mL of 10% NaOH and 75 mL of water. The quenching process generates hydrogen and is therefore carried out under a nitrogen purge. Allow the quenched solution to warm slowly to room temperature and then drain it from the reactor into a Buchner funnel. The solid thus collected is washed with hot THF (3 × 300 mL). Remove the volatiles from the combined filtrates on a rotary evaporator to obtain 35 g of a pale yellow solid. Dissolve the solid in hot ethanol, filter, and remove the solvent on a rotary evaporator. Dry overnight in a vacuum oven to leave 32.3 g of a pale yellow product (77.1% yield, ca. 97% purity). 1 1H NMR (400 MHz, DMSO). δ 7.46 (d, J - 6.8 Hz, 4H), 7.39 (dd, J = 8.6, 6.4 Hz, 2H), 4.99 (t, J = 5.3 Hz, 4H), 3.94 (d, J = 5.3 Hz, 8H) ppm. 13 13C NMR (400 MHz, DMSO) δ 139.3, 133.1, 127.3, 125.4, 60.4 ppm.

[0128]

[0129] Synthesis of 2,2',6,6'-Tetrakis(chloromethyl)-1,1'-biphenyl.The 5 L reactor was dried and purged with nitrogen overnight, and then 1,1'-biphenyl-2,2',6,6'-tetramethanol (45 g; 0.164 mol), dichloromethane (450 mL), and dimethylformamide (1 mL) were added. The resulting yellow solution was stirred and cooled to 0 °C. Then, thionyl chloride (1,071 g, 9.01 mol) was slowly added via a peristaltic pump over a 2-hour period, maintaining the reactor temperature near 0 °C; during the addition, the reactor was purged with nitrogen to remove the evolved HCl and SO2, and the exhaust gases passed through a water scrubber. The reaction solution was then warmed to room temperature and stirred for 30 minutes, and then heated to reflux (ca. 45 °C) overnight. The next day, the solution was cooled to 15 °C and drained from the reactor. Dichloromethane was removed by distillation at atmospheric pressure, and the residual thionyl chloride was removed by vacuum distillation. The resulting residue was first dried on a rotary evaporator and then dried in a vacuum oven at 60 °C overnight to give 58.1 g of a yellow solid. (100% yield, ca. 95% purity). 1 1H NMR (400 MHz, CDCl2) δ 7.66 - 7.60 (m, 4H), 7.56 (dd, J = 8.8, 6.4 Hz, 2H), 4.28 (s, 8H) ppm. 13 13C NMR (400 MHz, CDCl2) δ 136.9, 135.5, 131.3, 130.3, 45.0 ppm.

[0130]

[0131] Synthesis of (Biphenyl-2,2',6,6'-tetramethanediyl)tetrakis(diphenylphosphine) (Ligand A).Lithium wire (2.1 g, 300 mmol) was cut into small pieces and placed together with anhydrous THF (130 mL) into a 250 mL flask in a dry box. The suspension solution was transferred to a Schlenk line and cooled in an ice-water bath under nitrogen. Dichlorophenylphosphine (28.1 mL, 151.7 mmol) was added dropwise over 50 minutes at 0 °C, and then stirred for another 30 minutes at 0 °C. During this period, the color changed from turbid yellow to red. The solution was transferred to the dry box and stirred overnight at room temperature. The next morning, the solution was filtered through a cannula into a clean, dry 500 mL round-bottom flask, transferred to the Schlenk line and cooled to -78 °C. A solution of 2,2',6,6'-tetrakis(chloromethyl)-1,1'-biphenyl (12.7 g, 37 mmol) in THF (60 mL) was added dropwise over 50 minutes, and then cooled and stirred for another 20 minutes. Then the solution was slowly warmed to room temperature, then transferred to the dry box and stirred overnight. Then degassed dichloromethane (300 mL) and water (150 mL) were added, and the resulting mixture was separated. The lower layer was transferred to a round-bottom flask and concentrated on a rotary evaporator at 30 °C to give a solution of the crude product in THF. While heating this solution at 65 °C under flowing nitrogen, degassed ethanol (100 mL) was slowly added. During the ethanol addition, a white solid began to precipitate. Then the mixture was cooled and placed in the refrigerator overnight; the next day the resulting solid was collected by filtration in the dry box and washed with ethanol (2 × 50 mL). Dried under vacuum overnight, the desired product was obtained as a white powder (90% yield, 99% purity). 31 31P NMR (400 MHz, CDCl3) δ -14.5 ppm. 1 1H NMR (400 MHz, CDCl3) δ 7.30 - 7.17 (m, 40H), 6.91 - 6.82 (m, 2H), 6.72 (d, J = 7.7 Hz, 4H), 3.21 (s, 8H) ppm. The ligand A tetraphosphine has the following structure:

[0132]

[0133] Comparison with Ligand B

[0134] The comparative ligand B is BISBI (neither a monophosphine nor a tetradentate phosphine), which is known to be able to produce a hydroformylation catalyst with activity and selectivity. The preparation method of BISBI and examples of its use as a hydroformylation ligand can be found, for example, in US Patent No. 4,694,109. The BISBI used in the following comparative experiments was purchased from Proactive Molecular Research in Alachua County, Florida and used as received. The structure of BISBI (ligand B) is shown in formula 2.

[0135]

[0136] General Procedure

[0137] Unless otherwise indicated, the examples and comparative experiments were conducted in a 90 mL flow-through Fisher Porter reactor equipped with components for accurate temperature and gas flow control. The reactor off-gas was analyzed by on-line GC to determine the partial pressures. Mixing in the flow reactor was achieved by a continuous gas stream via a sparger at the bottom of the reactor. The design of this reactor is described in detail in U.S. Patent No. 5,731,472, the teachings of which are incorporated by reference.

[0138] The reaction rate is expressed as the number of moles of aldehyde produced per unit time per volume of catalyst solution (mol / L-h); this value is additionally divided by the propylene partial pressure to help attenuate the effect of inevitable small fluctuations in the propylene feed rate (rate / olefin). The product selectivity is expressed as the ratio of linear (n-) aldehyde to branched (iso-) aldehyde (N:I).

[0139] These examples used an accelerated test procedure (referred to herein as the closed procedure) to demonstrate the effect of the separation zone on the catalyst. The test procedure involved subjecting the dissolved activated rhodium complex catalyst to low partial pressure and high temperature for a much longer duration than that experienced during a normal continuous liquid recycle hydroformylation process in order to obtain meaningful results in a practical manner. For example, the catalytic deactivation and / or ligand usage discussed herein that may occur during continuous liquid recycle hydroformylation may take weeks to be quantitatively defined under normal aldehyde distillation recovery procedures because the catalyst is subjected to the evaporator conditions for only about a few minutes per day, while the accelerated test (closed procedure) can be completed within hours or days by continuously maintaining the reaction product fluid at a high aldehyde recovery type distillation temperature for an extended period of time. The closed section includes the period during which the reactor is sealed at reduced pressure and high temperature. This procedure is designed to simulate the effect of the separation zone on the catalyst solution.

[0140] Comparative Experiment A

[0141] Add diglyme (20 mL), rhodium (200 ppm) and ligand A (1.5 equiv) to the reactor. Hydroformylation was established at 90 °C under 20 psi CO, 50 psi H2 and 20 psi propylene, and the baseline hydroformylation rate and N:I were measured. After running overnight, the reactor was sampled for HPLC to determine the concentration of free ligand A, the reactor was vented to a total pressure of 10 psi and sealed overnight at 115 °C. After sealing in the section, hydroformylation was restarted under the original conditions and the catalyst solution was sampled for HPLC; then the sealing in the procedure was repeated a second time.

[0142] Comparative experiment B

[0143] Repeat the procedure of Comparative experiment A, except for the amount of added ligand A (5 equiv).

[0144] Examples 1-4

[0145] Repeat the procedures of Comparative experiments A and B, but add TPP (5 or 10 wt%).

[0146] The results of Comparative experiments A and B and Examples 8-11 are shown in Tables 1 and 2.

[0147] Table 1

[0148]

[0149] Table 2

[0150]

[0151] Catalyst solutions consisting only of rhodium and ligand A (Comparative experiments A and B) exhibited a significant decrease in hydroformylation rate and N:I after the sealing procedure, as did the concentration of free ligand A indicating ligand degradation. Although the initial hydroformylation rate was low in Examples 1-4, the catalyst solutions of the present invention showed the ability to withstand sealing in the conditions in terms of reducing the degree of catalyst deactivation and lowering the ligand usage rate. Since chelating ligands are usually expensive, reducing the consumption of tetradentate phosphines will improve the process economy.

[0152] Comparative experiments C-D

[0153] Repeat the procedures of Comparative experiments A and B, but use comparative ligand B.

[0154] Comparative experiments E-H

[0155] Repeat the procedures of Examples 1-4, but use comparative ligand B.

[0156] The results of Comparative experiments CH are summarized in Table 3.

[0157] Table 3

[0158]

[0159] It should be noted that, in terms of catalyst deactivation and N:I, the catalyst consisting only of rhodium and comparative ligand B is adversely affected by the shut-down period. Although the catalyst composed of rhodium, TPP, and comparative ligand B also shows improved stability, it does not exhibit an N:I exceeding 11. Without being bound by theory, this low N:I indicates that the rhodium-BISBI catalyst is more easily inhibited by TPP, and thus the resulting mixture of active complexes contains a relatively low amount of the active and selective rhodium-BISBI complex.

[0160] Examples 5 - 10

[0161] To each of six reactors was added diglyme (20 mL), rhodium (200 ppm), ligand A (1.5 or 3 equivalents), and TPP (3 - 5 wt%). Hydroformylation was established at 90 °C under 20 psi CO, 50 psi H2, and 20 psi propylene, and the baseline hydroformylation rate and N:I were measured. The reactors were shut down twice overnight at 10 psi and 115 °C; after each shut-down in the period, the catalyst performance was determined under the original pre-shut-down conditions. Subsequently, additional ligand A (one equivalent) was added to each reactor, and the resulting performance changes were measured. The results are summarized in Table 4.

[0162] Table 4

[0163]

[0164] It was noted that the initial hydroformylation rate is inversely proportional to the TPP concentration, and the N:I is proportional to the ligand A concentration; furthermore, the ability to increase the N:I by adding more ligand A at the end of the experiment was demonstrated. Without being bound by theory, this indicates that the observed catalysis is the result of a mixture of active rhodium complexes, and furthermore, some amount of rhodium exists in a relatively inactivated form, presumably the rhodium-triphosphine complex formed by both ligand A and TPP. Adding more ligand A restored the N:I to the original value (before the shut-down period), indicating that the system can recover after the initial degradation of ligand A.

[0165] Comparative Experiment I

[0166] To a reactor at 90 °C was added diglyme (20 mL), rhodium (350 ppm), and ligand A (4 equivalents). The reactor was briefly purged with 1:1 syngas and then sampled for HPLC to determine the concentration of free ligand A. Then air was bubbled into the solution through a syringe (250 mL), and the catalyst solution was sampled again for HPLC to determine the change in ligand A concentration.

[0167] Example 11.

[0168] Repeat the steps of Comparative Experiment I, but add TPP (12% by weight).

[0169] The results of Comparative Experiment I and Example 11 are summarized in Table 5.

[0170] Table 5

[0171]

[0172] The results in Table 5 show that the presence of TPP helps protect the tetraphosphine from degradation due to oxidation that may occur during continuous operation, possibly due to small leaks in the system or accidental introduction of air during equipment maintenance, etc.

Claims

1. A method for slowing down catalyst deactivation and / or slowing down the use of a tetraphosphine ligand during a hydroformylation process, the method comprising: (a) contacting an olefin with carbon monoxide, hydrogen, and a catalyst, wherein the olefin is propylene and the catalyst comprises (A) a transition metal and (B) a tetraphosphine having the following structure: where each P is a phosphorus atom and R 1 -R 46 each of which is independently hydrogen, a C1 to C8 alkyl group, an aryl group, an alkaryl group or a halogen, and (C) a monophosphine having the following structure: wherein P is a phosphorus atom and each of Y 1 -Y 3 is independently an aryl, alkaryl, cycloalkyl, benzyl, C3 to C8 alkyl, alkoxy having 1 to 8 carbon atoms, aryloxy or halogen, and the contacting is carried out in one or more reaction zones and under hydroformylation conditions; and (b) adding an additional monophosphine having the above structure to the reaction zone, wherein the amount of the monophosphine added to the reactor zone is greater than 1.5% by weight of the reaction fluid in the reaction zone based on the total weight of the reaction fluid in the reaction zone.

2. The method according to claim 1, wherein the monophosphine is triphenylphosphine.

3. The method according to claim 1, wherein the monophosphine is a bulky monophosphine.

4. The method according to any one of claims 1-3, wherein the transition metal comprises rhodium.

5. The method according to any one of claims 1-3, wherein each R 1 -R 46 is hydrogen.

6. The method according to claim 1, wherein the decrease in the hydroformylation rate over time is less than the decrease in the hydroformylation rate in a process under the same conditions but lacking the monophosphine.

7. The method according to claim 1, wherein the rate of use of the tetraphosphine ligand in the hydroformylation process is less than the rate of use of the tetraphosphine ligand in a hydroformylation process under the same conditions but lacking the monophosphine.

8. The method according to any one of claims 1-3, wherein the amount of the monophosphine added is at least 40 moles of phosphine per mole of transition metal.

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