HK1024465B - Process for the preparation of an aldehyde - Google Patents

Description

Preparation method of aldehyde

The invention relates to a method for producing aldehydes by subjecting unsaturated organic compounds to a hydroformylation reaction in the presence of a catalyst system comprising rhodium or iridium and a multidentate organophosphite ligand.

The hydroformylation reaction is a reaction in which an unsaturated compound is reacted with hydrogen and carbon monoxide in the presence of a catalyst system to obtain an aldehyde compound.

Such A process is described in WO-A-9518089. WO-A-9518089 describes the preparation of methyl 5-formylvalerate by hydroformylation of methyl 3-pentenoate in the presence of A catalyst system comprising rhodium and A multidentate organophosphite ligand.

One disadvantage of this process is that the multidentate phosphite ligands prove to be sensitive to degradation in the presence of traces of oxygen or other oxidizing compounds such as hydroperoxides that may be present during the reaction. For example, oxygen may leak into the process during continuous operation. The degradation of the ligands is disadvantageous in that new ligands have to be added to the system in order to ensure that the activity and selectivity of the reaction towards the aldehyde compound is maintained at the desired level for a long period of time. The addition of such large amounts of new ligand per kilogram of aldehyde product is not attractive from an economic standpoint, the type of phosphite ligand, and the relatively high cost of the aldehyde product.

The object of the present invention is a process wherein less phosphite ligand is consumed per kg of aldehyde product in the presence of traces of oxygen than in the process according to the state of the art.

This is achieved in the presence of a bidentate phosphine.

We have found that less multidentate phosphite ligand can be consumed per kilogram of aldehyde product using the process according to the invention, while the selectivity of the reaction remains practically at the same level. This is unexpected because monodentate phosphines are well known ligands and it was thought that the addition of these additional ligands would negatively affect the selectivity of the (linear) aldehyde product.

Another advantage of the process according to the invention is that the relatively expensive multidentate phosphite ligands are protected as if monodentate phosphines were added. Although the phosphine is selectively oxidized in the process according to the invention, this is not tasteful either, since the phosphine is much cheaper than the phosphite. The advantages mentioned above are further enhanced if the process for preparing aldehydes by hydroformylation of unsaturated organic compounds is carried out as a continuous process. It is an extremely important factor in continuous processes since the selectivity can be used several times to repeatedly without negative effects.

U.S. Pat. No. 4, 4169861 describes the preparation of alkanals by hydroformylation of alphA-olefins in the presence of A catalyst system comprising rhodium, A bidentate phosphine ligand and A monodentate phosphine ligand, the monodentate ligand being A phosphine having A steric hindrance parameter thetA of 135-150 deg.. The document does not mention multidentate phosphite ligands as part of the catalyst system.

Without wishing to be bound by the following theory, the applicants believe that the decomposition of the multidentate phosphite ligand may be due to oxygen present during the hydroformylation reaction and/or during further processing of the resulting reaction mixture. For example, the feedstock and/or solvent may contain trace amounts of oxygen. Oxygen can also be present in the production facilities of industrial hydroformylation reactions, for example, as a result of leakage into the facilities.

When C of 3-pentenoic acid is mentioned in EP-A-662468₁-C₆When an alkyl ester (alkyl pentenoate) is used as starting material, we have found that the ligand selectivity for oxygen is particularly high. The hydroperoxide compound may be formed as a result of the reaction of the oxygen with the alkyl pentenoate.

The monodentate phosphines according to the invention may be of the general formula P (R')₃Wherein R' is an organic group. Preferably, the organic radical R 'is an aliphatic, cycloaliphatic or aromatic radical having from 1 to 20 carbon atoms, preferably from 5 to 12 carbon atoms, and the three R' radicals may be identical or different. The R' group may contain 1 or more heteroatoms, such as oxygen, nitrogen or halogen.

Examples of monodentate phosphines according to the invention are trimethylphosphine, triethylphosphine, tributylphosphine, tripropylphosphine, tris (propylnitrile) phosphine, diethylphenylphosphine, diphenylmethylphosphine, diphenylethylphosphine, tris (trifluoromethyl) phosphine, tris (isobutyl) phosphine, triphenylphosphine, tris (p-tolyl) phosphine, tris (m-fluorophenyl) phosphine, isopropyldiphenylphosphine, tris (isopropylphosphine), tris (sec-butyl) phosphine, tribenzylphosphine, tricyclohexylphosphine, dicyclohexylphenylphosphine, di (tert-butyl) phenylphosphine, trineopentylphosphine, tris (tert-butyl) phosphine, tris (o-methoxyphenyl) phosphine, tris (pentafluorophenyl) phosphine, tris (o-tolyl) phosphine and tris * -ylphosphine. Mixtures of two or more of these compounds are also suitable as the monodentate phosphine.

We have found that in the process according to the invention, the PR 'is preferably selected'₃The organic group R' of the phosphine is such that the steric hindrance parameter θ of the phosphine is 160-220 °, preferably 170-210 °. We have also found that the activity of the reaction is not adversely affected when these phosphine compounds are used.

The steric hindrance parameter theta is 2.28 * (10) from the center of the phosphorus atom^-10Meter) is the apex angle of the cone, which just touches the symmetrical P (R')₃The van der Waals radius of the outer atom of said R' substituent of the phosphine (see "chemical reviews, 1977, Vol. 77, pp. 313-348" and U.S. Pat. No. A-4169861, C.A. Tolman).

Asymmetric PR'₃Phosphines (where at least 1 of the 3R 'groups is different from the other R' groups, e.g. PRThe steric hindrance parameter θ of ' R ' ") can be aided by a corresponding symmetric phosphine PR '₃、PR”₃And PR'₃The apex angle of (c) is calculated using the following equation:

examples of such monodentate phosphines having a steric hindrance parameter theta of 160-220 deg. have been mentioned above. Preferably, the monodentate phosphine having a steric hindrance parameter θ of 160-220 ° is trineopentylphosphine, tri (tert-butyl) phosphine, or tri (o-tolyl) phosphine.

Most preferably tri (o-tolyl) phosphine is used as the monodentate phosphine in the process according to the invention. Tris (o-tolyl) phosphine is inexpensive, readily available, and exhibits high efficacy when used in small amounts.

The monodentate phosphine may be added to the hydroformylation reaction mixture or it may already be present in the reaction mixture which also contains the unsaturated organic compound, rhodium or iridium and the multidentate phosphite ligand.

The concentration of monodentate phosphines in the hydroformylation reaction mixture according to the invention is preferably an effective amount sufficient to prevent degradation of the multidentate phosphite ligand. Specifically, the amount is 1 to 40 moles per mole of multidentate phosphite ligand, preferably 2 to 10 moles per mole of multidentate phosphite ligand.

The multidentate phosphite ligand preferably has the following general structure:

wherein n is 2-6, X is an n-valent organic bridging group, R¹And R²Independently of one another, two organic monovalent aryl radicals and/or one divalent diaryl radical.

R¹And R²Preferably a monovalent organic group having 1 to 20 carbon atoms, or R¹And R²Together form a divalent organic radical having from 6 to 30 carbon atoms. Most preferred is R¹And R²Is a monovalent aryl group having 6 to 14 carbon atoms. Different R¹And R²The groups may be different in the ligand. For example, some R in the same ligand¹And R²The groups may be divalent and the other R groups¹And R²The group is a monovalent group.

X is preferably an organic group having 1 to 40 carbon atoms, more preferably 6 to 30 carbon atoms. Examples of ligands having tetravalent organic radicals are ligands having a bridging group corresponding to pentaerythritol. Bidentate ligands having divalent bridging groups are most often mentioned in this patent document. Examples of such phosphite ligands are described in U.S. Pat. No. 4,4748261, EP-A-556681 and EP-A-518241.

When an internally ethylenically unsaturated organic compound such as 2-butene or 3-pentenoate is used as the starting material for preparing the terminal aldehyde, it is preferred to employ a multidentate phosphite ligand which forms a chelate-type complex with the metal (rhodium or iridium) used in the reaction zone. Chelate-type complexes mean that at least 2 phosphorus P atoms of the (substantially) ligand molecule form a coordinate bond with 1 rhodium or iridium atom per ion. Non-chelating complexes present ligand molecules with only 1 phosphorus P atom forming a coordinate bond with 1 rhodium or iridium atom/ion. The choice of bridging group X of the ligand will determine whether a chelating complex can be formed in the reaction zone. Examples of bridging groups which give ligands which can form chelating bridging groups are described in WO-A-9518089.

The ligands preferably used in the process according to the invention have a2, 2 ' -dihydroxy-1, 1 ' -binaphthyl bridging group which is preferably substituted in the 3 and 3 ' positions. The ligand may be represented by the general formula:wherein Y and Z are substituents other than hydrogen, R¹And R²Are identical or different substituted monovalent aryl radicals and/or are linked to 1 phosphorus atom to form-O-R³OR of the-O-group¹And OR²Any one of (1), R³Is a divalent organic radical containing 1 or 2 aryl groups.

The substituents Y and Z are preferably identical or different organic radicals having at least 1 carbon atom, more preferably from 1 to 20 carbon atoms.

Preferably, Y and Z are independently selected from the group consisting of alkyl, aryl, triarylsilyl, trialkylsilyl, carbonylalkoxy, carbonylaryloxy, aryloxy, alkoxy, alkylcarbonyl, arylcarbonyl, oxazole, amide, amine or nitrile containing groups.

For Y and Z, the alkyl group is preferably C₁-C₁₀Alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, tert-butyl, isobutyl, pentyl or hexyl. Examples of suitable triarylsilyl groups are triphenylsilyl groups, suitableExamples of trialkylsilyl groups are trimethylsilyl and triethylsilyl. Preferred aryl groups have 6 to 20 carbon atoms, such as phenyl, benzyl, tolyl, naphthyl, anthryl or phenanthryl. Preferred aryloxy groups have 6 to 12 carbon atoms, such as phenoxy. Preferred alkoxy groups have 1 to 20 carbon atoms, such as methoxy, ethoxy, tert-butoxy or isopropoxy. Preferred alkylcarbonyl groups have 2 to 12 carbon atoms, such as methylcarbonyl, tert-butylcarbonyl. Preferred arylcarbonyl groups have 7 to 13 carbon atoms, such as phenylcarbonyl. Preferred amide groups contain C₁-C₄Alkyl groups, preferably amine groups, containing 2C₁-C₅An alkyl group.

Most preferably Y and Z are independently carbonylalkoxy or carbonylaryloxy-CO₂R, wherein R is C₁-C₂₀Alkyl radicals or C₆-C₁₂Aryl radical, preferably C₁-C₈An alkyl group. Examples of suitable R groups are methyl, ethyl, propyl, isopropyl, n-butyl, t-butyl, isobutyl, phenyl and tolyl. Even more preferably, both Y and Z are the same carbonylaryloxy group, more preferably the same carbonylalkoxy group, since the resulting ligand is more readily available.

The 2, 2 '-dihydroxy-1, 1' -binaphthyl bridging group can optionally be further substituted with other groups such as a halogen, e.g., Cl or F, or one of the substituents R that may be present on the bridging group as described above.

R¹And R²Preferably identical or different monovalent aryl groups, more preferably aryl groups having from 6 to 20 carbon atoms. It is understood that all 4R¹And R²The groups may all be different. Preferably all 4 groups are the same, since the resulting ligand is more readily available. OR, OR¹And OR²(attached to the same P atom) may form-O-R³-O-group, wherein R³Is a divalent group of 6 to 40 carbon atoms containing 1 or 2 aryl groups. Preferably R¹And R²In the ortho position relative to the oxygen atom, the same or differentContaining at least 1R other than hydrogen⁴Monovalent aryl radicals of radicals, preferably C₆-C₂₀Aryl radicals such as phenyl, in which R⁴Is C₁-C₂₀Alkyl or C₆-C₂₀Aryl radical, preferably C₁-C₆An alkyl group. To R¹And R²Other preferred monovalent aryl groups are, in particular, monovalent fused aromatic ring systems having 2 or more rings of 10 to 20 carbon atoms. R¹And R²Optionally further coated with, for example, C₁-C₁₀Alkyl radical, C₆-C₂₀Aryl radical, C₁-C₁₀Alkoxy or C₆-C₂₀Aryloxy groups or halogen groups such as F, Cl or Br or amine groups.

When the aryl radical R¹And R²By at least 1R in ortho-position relative to the phenolic oxygen atom⁴When substituted by groups, these ligands can be used in hydroformylation processes with high linear selectivity. These R⁴Examples of radicals are methyl, ethyl, propyl, isopropyl, isobutyl, tert-butyl or n-butyl. For R⁴In particular, it is preferred that only 1 bulky group (bulk group) having isopropyl group or higher steric hindrance is ortho-substituted on the aryl group. When less bulky substituents are used, the 2 ortho positions are preferably substituted by these groups. For R¹And R²Preferred R is⁴The substituted aryl group is a 2-isopropylphenyl or 2-tert-butylphenyl group.

For R¹And R²Another preferred class of aryl groups comprises fused aromatic ring systems of 2 or more rings having 10 to 20 carbon atoms, which do not necessarily have to be substituted at the carbon atom adjacent to the carbon atom bonded to the oxygen atom in formula (4) by a group other than hydrogen. We have found that when R is¹And/or R²With such unsubstituted aromatic ring systems, high catalyst activity, high selectivity to terminal aldehydes and high linearity are obtained. Examples of such fused aromatic ring systems are phenanthryl, anthracyl and naphthyl groups. Preference is given to using 9-phenanthryl or 1-naphthyl groups. What is needed isThe aromatic ring system may optionally be substituted, for example, in positions other than the ortho-positions described above in the ring system, with various substituents, for example, as described above.

R¹And R²Are linked to form a divalent radical R³Is exemplified by C₆-C₂₅Diaryl groups, such as 2, 2 '-biphenyldiyl or 2, 2' -binaphthyl-diyl groups.

These ligands can be prepared by various methods known in the art; see, for example, the descriptions in US-A-4769498, US-A-4688651 and j.amer.chem.soc., 1993, volume 115, page 2066. The organobidentate phosphite compounds according to the present invention may be prepared using 3-or 3, 3 ' -substituted 2, 2 ' -dihydroxy-1, 1 ' -binaphthyl bridging compounds. The binaphthol bridged compounds can be prepared by the methods described in Tetrahedron lettt.1990, 31(3), p 413-416 or in j.am.chem.soc.1954, vol 76, p 296 and in org.proc.prep. international, 1991, vol 23, p 200. These binaphthol bridged compounds are prepared by reacting these binaphthol bridged compounds with PCl by the method described in the above-mentioned U.S. Pat. No. 5,235,113₃Treatment R¹OH and/or R²Phoro-chlorides (R) from OH¹O)(R²O) PCl together can produce the phosphite compound.

The catalyst system used in the process according to the invention can be prepared according to well-known complex formation methods by mixing a suitable rhodium or iridium compound, optionally in a suitable solvent, with the phosphite ligand. The solvent is generally the solvent used in the hydroformylation reaction. Suitable rhodium and iridium compounds are, for example, hydrides, halides, organic acid salts, acetylacetonates, inorganic acid salts, oxides, carbonyl compounds and amine compounds of these metals. Examples of suitable catalyst precursors are Ir (CO)₂(acac)、Ir₄(CO)₁₂、Rh(OAc)₃、Rh₂O₃、Rh(acac)(CO)₂、Rh(CO)₂(DPM)、[Rh(OAc)(COD)]₂、Rh₄(CO)₁₂、Rh₆(CO)₁₆、RhH(CO)(Ph₃P)₃、[Rh(OAc)(CO)₂]₂And [ RhCl (COD)]₂(wherein "acac" is an acetylacetonate group, "Ac" is an acetyl group, "COD" is 1, 5-cyclooctadiene, "Ph" is a phenyl group, and DPM is a2, 2, 6, 6, -tetramethyl-3, 5-pimelate group). It should be noted, however, that the rhodium and iridium compounds are not necessarily limited to the above compounds.

The metal is preferably rhodium.

The process according to the invention is particularly advantageous when preparing terminal (or linear) aldehyde compounds.

The unsaturated organic compounds which are hydroformylated to form aldehydes by the process according to the invention have at least 1 ethylenically unsaturated ("C ═ C") bond in the molecule and usually have from 2 to 20 carbon atoms. Examples of suitable unsaturated organic compounds are linear, terminally unsaturated olefins, such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-nonene, 1-decene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene and 1-dodecene; branched terminally unsaturated olefins such as isobutylene and 2-methyl-1-butene; linear internally unsaturated olefins such as cis-and trans-2-butene, cis-and trans-2-hexene, cis-and trans-3-hexene, cis-and trans-2-octene and cis-and trans-3-octene; branched internally unsaturated olefins such as 2, 3-dimethyl-2-butene, 2-methyl-2-butene and 2-methyl-2-pentene; mixtures of terminally and internally unsaturated olefins, such as octene produced by dimerization of butenes, olefin-oligomer-isomer mixtures of dimer-tetramer of lower olefins (including propylene, n-butene, isobutene), and cycloaliphatic unsaturated olefins such as cyclopentene, cyclohexene, 1-methylcyclohexene, cyclooctene and limonene. Preferably, the unsaturated organic compound is an internally unsaturated compound having 4 to 20 carbon atoms.

Suitable unsaturated organic compounds are olefins having aromatic substituents, such as styrene, alpha-methylstyrene and allylbenzene; diene compounds such as 1, 5-hexadiene, 1, 7-octadiene and norbornadiene are also suitable unsaturated olefins.

The unsaturated organic compound may be substituted with 1 or more than 1 functional group. The functional group contains 1 or more than 1 heteroatom (which may be the same or different from each other), such as oxygen, sulfur, nitrogen or phosphorus. Examples of such unsaturated organic compounds are vinyl methyl ether, methyl oleate, oleyl alcohol, methyl 2-pentenoate, methyl 3-pentenoate, methyl 4-pentenoate, 3-pentenoic acid, 4-pentenoic acid, 2-pentenenitrile, 3-pentenenitrile, 4-pentenenitrile, 2-pentenal, 3-pentenal, 4-hydroxy-1, 7-octadiene, 1-hydroxy-3, 7-octadiene, 1-methoxy-3, 7-octadiene, 7-octene-1-al, acrylonitrile, esters of acrylic acid and methacrylic acid, esters of methacrylic acid, methyl methacrylate, vinyl acetate and 1-acetoxy-3, 7-octadiene.

The process according to the invention can be carried out in a particularly preferred manner as a starting material for an internally unsaturated olefin having from 4 to 20 carbon atoms in a process for preparing a terminal (linear) aldehyde compound. Examples of such internally unsaturated olefins have already been mentioned above. It is preferred to use an internally unsaturated olefin substituted with 1 or more functional groups according to the following formula (5):

CH₃-CR⁵＝CR⁶-R⁷(5) wherein R is⁵And R⁶Is a hydrocarbon radical or preferably hydrogen, R⁷Is cyano or hydrocarbyl, whether substituted with 1 or more than 1 functional group containing a heteroatom such as oxygen, sulfur, nitrogen or phosphorus. Preference is given to using internally unsaturated olefins having from 4 to 20 carbon atoms according to formula (5), in which R⁵And R⁶Is hydrogen.

An internally unsaturated olefin having 4 to 20 carbon atoms according to formula (5) (wherein R⁵And R⁶Hydrogen) are 2-pentenenitrile, 3-pentenoic acid and C of 3-pentenoic acid₁-C₆An alkyl ester. We have found that these compounds are well converted to the corresponding linear aldehyde compounds using the process according to the invention. These aldehydesCompounds, particularly methyl 5-formylvalerate, are intermediates in the preparation of epsilon caprolactam or adipic acid (which in turn are starting materials for the preparation of nylon-6 and nylon-6, respectively). 3-pentenoic acid C₁-C₆Examples of-alkyl esters are methyl-, ethyl-, propyl-, isopropyl-, tert-butyl-, pentyl-and cyclohexyl-3-pentenoate. The use of methyl-and ethyl-3-pentenoate is preferred, since these compounds are readily available. 3-pentenenitrile, 3-pentenoic acid and C of pentenoic acid₁-C₆The alkyl esters may be C's which also contain 2-and 4-pentenenitrile, 2-and 4-pentenoic acid and 2-and 4-pentenoic acid, respectively₁-C₆A mixture of alkyl esters is present in the reaction mixture.

The concentration of rhodium or iridium (compound) in the reaction mixture may be in the range 1 to 5000ppm rhodium or iridium. This concentration is preferably 50-1000 ppm.

The molar ratio of multidentate phosphite ligand to rhodium or iridium is generally from 0.5 to 100, preferably from 1 to 10, more preferably less than 1.2, and most preferably from 1 to 1.2 (moles ligand per mole metal). Preferably this ratio is greater than 1.05. Small changes in the ligand or rhodium concentration will not automatically result in a decrease in the yield of the aldehyde compound. We have found that by carrying out the process according to the invention with a slight molar excess of ligand over rhodium, the rate of ligand degradation is further reduced. When the process according to the invention is carried out by slightly molar excess of the ligand to rhodium (or iridium), it is desirable to monitor the ligand concentration and degradation for reasons other than oxidation to add new ligand during the continuous process and to maintain it within the preferred operating range.

The reaction mixture can act as a solvent in the process according to the invention, so that in general no further solvent has to be added. The reaction mixture is a mixture of the various reactants of the hydroformylation, such as unsaturated organic compounds, aldehydes and/or by-products formed, in particular high-boiling by-products. If a further solvent is added, saturated hydrocarbons such as naphtha, kerosene, mineral oil or cyclohexane, or aromatics such as toluene, benzene, xylene, or ethers such as diphenyl ether,Tetrahydrofuran, or ketones such as cyclohexanone, or nitriles such as benzonitrile, texanol^*Or tetraglyme^*(Union Carbide) is suitable as an additional solvent. Mixtures of 2 or more than 2 of these compounds are also suitable as further solvents.

The reaction conditions of the hydroformylation reaction in the process according to the invention will depend on the particular initially unsaturated organic compound.

The reaction temperature is generally from room temperature to 200 ℃ and preferably from 50 to 150 ℃.

The reaction pressure is generally from 0.1 to 20MPa, preferably from 0.15 to 10MPa, most preferably from 0.2 to 1 MPa.

The molar ratio of hydrogen to carbon monoxide is generally from 10: 1 to 1: 10, preferably from 6: 1 to 1: 2.

The reaction according to the invention can be carried out in gas/liquid contactors known to the person skilled in the art. Examples of suitable reactors are bubble columns, sieve plate columns, gas-liquid stirred reactors.

The process according to the invention can be carried out batchwise or preferably in a continuous process. In an industrial process, the reaction is preferably carried out in a continuous mode. The continuous process can be started, for example, by feeding the rhodium or iridium compound, multidentate phosphite ligand and monodentate phosphine to the reactor in one operating step, and after increasing the temperature, unsaturated organic compound, carbon monoxide and hydrogen are added to the reaction mixture in continuous mode or batchwise. The effluent from the reactor contains the aldehyde product, rhodium or iridium compounds, multidentate phosphite ligands, monodentate phosphines, phosphine oxides, carbon monoxide, hydrogen and optionally solvent. Carbon monoxide and hydrogen can be separated from the reaction mixture by reducing the pressure to, for example, 0.1 Mpa. The aldehyde can be removed from the resulting mixture in 1 or more than 1 separation step. The rhodium or iridium compounds, polydentate phosphites, monodentate phosphines and phosphine oxides are preferably recycled to the reactor and reused in the process according to the invention. The separation step is preferably carried out by vacuum distillation at a pressure of 0.01-1Mpa, most preferably by vacuum distillation at a pressure of 0.01-0.1Mpa, for example in a rolling film evaporator. Another suitable separation method is the membrane separation method described, for example, in WO-A-9634687. Preferably, the aldehyde is prepared in a continuous process wherein the catalyst system is reused and fresh phosphine is added continuously or intermittently to the reaction process.

The aldehyde product can be separated from the reaction mixture using any separation technique known to those skilled in the art. Examples of suitable separation techniques are (vacuum) evaporation, crystallization and extraction with suitable extractants.

Preferably, the concentrations of the phosphine and the phosphite are determined continuously or periodically. If the concentration is below the stated value, for example due to degradation of these compounds, new compounds are added to the circulating reaction mixture. We have found that the degradation products of the phosphines do not have a negative effect on the activity and selectivity of the hydroformylation reaction.

Preferably, the catalyst system which is recycled is contacted with ｃA Lewis base as described in EP-A-285136. Most preferably, the Lewis base is an ion exchanger having basic groups, such as a polystyrene matrix containing basic groups (e.g., Amberlist A21)^*) The packed bed of (3).

One possible method according to the invention (for use in the various embodiments) is shown in figure 1. FIG. 1 will be illustrated in a non-limiting manner below to illustrate the preparation of methyl 5-formylvalerate using a rhodium/phosphite catalyst system.

In FIG. 1, methyl 3-pentenoate is fed to reactor (A) via stream (1). A catalyst system is present in reactor a. CO and H₂Is fed via stream (2) into reactor (A), while fresh monodentate phosphine is fed via stream (3) continuously or intermittently into reactor (A). Reaction comprising methyl 5-formylvalerate, various by-products, any unconverted methyl 3-pentenoate, catalyst system, phosphine, carbon monoxide and hydrogenThe effluent of vessel (A) is sent via stream (4) to a flash column (flash) (B). The pressure in the flash column (B) is reduced, for example to atmospheric pressure. Carbon monoxide and hydrogen are separated from the reaction mixture via stream (5) and recycled to reactor (a). The resulting liquid mixture is sent to separation step (C) via the resulting liquid stream (6). The mixture is subjected to vacuum distillation in the separation step (C). The majority of the volatile constituents, such as methyl-2-pentenoate, methyl-4-pentenoate, methyl valerate, the majority of unconverted methyl-3-pentenoate and a small amount of aldehyde product are removed via stream (7). Stream (7) is sent to separation step D. In the separation step D methyl valerate, methyl 4-pentenoate and methyl cis-2-pentenoate are discharged via stream (7 b). Methyl trans-2-pentenoate and methyl 3-pentenoate are recycled to reactor (A) via stream (7 a). The residual mixture of the separation step (C) is sent via stream (8) to the ion exchanger (E) of the packed bed of polystyrene matrix containing basic amine groups. The effluent (9) is sent to the separation step (F). In the separation step (F), the remaining part of the unreacted methyl-3-pentenoate, methyl-5-formylvalerate and the various branched isomers are separated from the catalyst system, the monodentate phosphine and the by-products by vacuum distillation. The residue is recycled to the reactor (A) via stream (10).

Preferably, a purge stream is present in the process to prevent the accumulation of various by-products and degradation products of the phosphine and phosphite compounds. These purge streams contain primarily a certain amount of rhodium/phosphite catalyst system. The rhodium concentration in such purge streams is typically greater than 100ppm rhodium and less than 2000ppm rhodium. For an industrially attractive process, it is necessary to recover from such a purge stream a catalyst system comprising the rhodium/phosphite ligand complex. The rhodium/phosphite ligand complex may advantageously be recovered from this purge stream by membrane separation as described in WO-A-9634687. These purge streams are not shown in the figure to prevent confusion.

Methyl 5-formylvalerate and branched isomers are removed via stream (11). Methyl 5-formylvalerate may be further purified, for example, by distillation. The ion exchanger E can also be located in the process at a location other than between the separation steps (C) and (F), for example between the reactor (A) and the flash column (B) or between the flash column (B) and the separation step (C) or between (F) and (A). Since degradation and/or loss of phosphite ligand via the purge stream cannot be avoided, a fresh catalyst system must be supplied to the circulating catalyst system.

The invention also relates to a composition comprising a group 8-10 metal, a multidentate organophosphite ligand as described above and a monodentate phosphine of formula PR'₃Represented by (a). The organic (R') group is preferably as described above. PR 'is preferably selected'₃The organic group R' of the phosphine is such that the steric hindrance parameter θ of the phosphine is 160-220 °, preferably 170-210 °.

The metal present in the catalyst system according to the invention is preferably rhodium. The catalyst system is particularly advantageous if it is used in the hydroformylation of internally unsaturated olefins as described above.

The catalyst system according to the invention can also be used, for example, as a cyanohydrogenation catalyst, a hydrogenation catalyst, a polymerization catalyst, an isomerization catalyst and a carbonylation catalyst.

The invention will be further illustrated by the following non-limiting examples. The conversion of methyl 3-pentenoate (M3P) was the percentage of M3P reacted. The selectivity to methyl 5-formylvalerate (M5FV) can be calculated as follows: the amount of M3P that had been converted to M5FV (moles/hour) was divided by the amount of M3P that had reacted (moles/hour).

Example I

To a volume of 1 liter Hastalloy B autoclave ((A) in FIG. 1), 200 g of the catalyst solution was added. The catalyst solution contains: 568 g of m-xylene, 1.105 g (4.3 mmol) of rhodium dicarbonyl acetylacetonate (Rh (acac) (CO)₂) 20.0 g (65.8 mmol) of tri- (o-tolyl) phosphine and 14.0 g (12.8 mmol) of bidentate phosphite ligand (M) of the following formula (5)_w＝1090)：300 g of methyl 3-pentenoate (M3P) (stream (1) in FIG. 1) were then added to the autoclave (reactor). CO/H at 1MPa₂Under pressure (1: 1 mol/mol CO/H₂) The reactor was heated to 95 ℃. Mixing CO with H₂Is continuously fed into the reactor (stream (2) in fig. 1), so that there is always an offgas stream flowing out of the reactor. The reactor may contain about 500 ml of liquid. Once the reactor contains more than about 500 ml of liquid, it overflows through the dip tube and this excess reaction mixture is then removed (stream (4) in figure 1). The reactor effluent stream contained more than 500 ml of liquid and the unreacted gas was reduced to atmospheric pressure by a back pressure regulating valve and fed to a gas-liquid separator ((B) in fig. 1). The gas was evacuated after passing through a condenser at 1 bar to remove the condensable fraction (stream (5) in fig. 1). The liquid collects in the bottom of the gas-liquid separator (stream (6) in fig. 1), from which it is sent through a control valve to a first short-path rolling-film evaporator ((C) in fig. 1). In the evaporator, most of the unreacted M3P, light by-products and a small amount of aldehyde product were evaporated under vacuum (78947Pa. wall temperature 90 ℃ C.). The liquid residue (stream (8) in FIG. 1) was passed through a column (FIG. 1 (E)) containing 7 grams of weakly basic Amberlist A21 resin. Where it (stream (9) in figure 1) is pumped to a second short-circuiting rolling film evaporator ((F) in figure 1). In the evaporator, the unreacted remainder of M3P and a portion of the MFV product were evaporated under a relatively high vacuum (13158Pa, heating temperature 90 ℃). The residue of the second evaporator (stream (10) in fig. 1) is pumped back to the reactor, whereby a cycle is formed. The temperature and pressure of the two evaporators are regulated to be in a stable operation state: the total liquid material volume was kept constant in the apparatus (about 1200 ml of liquid was returned to the reactor before distillation, if calculated). After 2 hours of reaction at 95 ℃, fresh M3P (stream (1) in fig. 1) was pumped into the reactor at a rate of 90 g/hour, while more catalyst solution was pumped at a rate of 80 g/hour. CO and H₂(stream (2) in the figure) was fed at a rate of 30N 1/hr. The pressure was set at 0.5 MPa. After about 4 hours all distillation and pumps were still operating and the catalyst was stopped. After a further 16 hours the device reached a steady state. At the point of stabilityThe Rh concentration in the reactor was about 300 ppm. The molar ratio Rh/phosphite was 1/3 and the molar ratio phosphine/phosphite was 5/1. Liquid samples were taken from the gas-liquid separator every 24 hours. The sampling should be done with great care, avoiding contact with oxygen and moisture, and various samples collected for analysis using carefully opened samplers in a dry box. Samples were analyzed for various organic and inorganic components using Gas Chromatography (GC), High Pressure Liquid Chromatography (HPLC), Nuclear Magnetic Resonance (NMR), and elemental analysis. After 210 hours from the start of the experiment, the composition of the liquid in the reactor was determined as follows: 0.39% by weight of methyl 4-pentenoate, 0.06% by weight of methyl cis-2-pentenoate, 1.82% by weight of methyl valerate, 9.17% by weight of methyl trans-3-pentenoate, 2.61% by weight of methyl cis-3-pentenoate, 4.48% by weight of methyl trans-2-pentenoate, 0.04% by weight of xylene, 0.48% by weight of methyl 2-formylvalerate, 1.06% by weight of methyl 3-formylvalerate, 1.61% by weight of methyl 4-formylvalerate, 71.89% by weight of methyl 5-formylvalerate (M5FV), 0.23% by weight of monomethyl adipate, 0.48% by weight of 3-hydroxybutyraldehyde condensation product, 0.64% by weight of tri (o-tolyl) phosphine, 0.44% by weight of tri (o-tolyl) phosphine-oxide and 4.6% by weight of phosphine-oxide A mass component and a catalyst component.

To ensure that the substrate was free of hydroperoxide, M3P was subjected to a batch distillation at atmospheric pressure over triphenylphosphine and passed through a column packed with alumina-oxide before being fed to the reactor. The distillate was collected continuously and analyzed for product composition. The reaction can run for 250 hours without significant oxidative degradation of the phosphite. However, after the reaction was complete, tris (o-tolyl) phosphine was oxidized by 68%. The selectivity during the reaction was 84-82%. The conversion varied slightly as the sampling from the unit varied from 79% to 77%. Comparative experiment A

Example I was repeated except that no tri (o-tolyl) phosphine was added to the catalyst solution. In this experiment, the reaction was carried out at 80% conversion to M3P and 82% selectivity to M5FV for 110 hours. After 110 hours of operation, the concentration of phosphite ligand starting materialReduced to sub-stoichiometric amounts compared to rhodium. The reaction rate increased significantly (conversion increased to 90%) while the selectivity (for M5FV) dropped dramatically (to 40%). Such as³¹P NMR showed that we found that all excess ligand was degraded (mainly as a result of oxidation).

Example II

Example I was repeated except that triphenylphosphine was added to the catalyst solution instead of tri (o-tolyl) phosphine. The molar ratio Rh/triphenylphosphine was 1/10. The reaction has the following characteristics: the reaction can run intact for 250 hours without the catalyst undergoing significant oxidation. But such as³¹P NMR showed that only 73% of the triphenylphosphine was finally oxidized.

The selectivity remained around 82% throughout the run (a small decrease was observed from 83% at the start of the run to 81% at the end). However, the conversion was only 63%.³¹The results of P NMR show that the lower catalyst activity is due to the interaction of the tri-phenylphosphine with the rhodium atom.

These examples clearly show that hindered phosphines such as tri (o-tolyl) phosphine can successfully protect expensive phosphite hydroformylation ligands from oxidative degradation without affecting the actual hydroformylation rate. While less hindered phosphines, such as triphenylphosphine, may also protect phosphite ligands from oxidative degradation, they also reduce the rate of hydroformylation of the catalyst.

Claims (24)

1. Process for the preparation of aldehydes by hydroformylation of unsaturated organic compounds in the presence of a catalyst system comprising rhodium or iridium and a multidentate organophosphite ligand, characterised in that a monodentate phosphine is present.

2. Process according to claim 1, characterized in that the steric hindrance parameter θ of the monodentate phosphine is 160-220 °.

3. Process according to any one of claims 1-2, characterized in that the steric hindrance parameter θ of the monodentate phosphine is 170 ° and 210 °.

4. Process according to any one of claims 1-2, characterized in that the monodentate phosphine is tri (o-tolyl) phosphine.

5. The process according to any of claims 1-2, characterized in that the hydroformylation reaction mixture contains from 1 to 40 moles of monodentate phosphine per mole of multidentate phosphite ligand.

6. The process according to any of claims 1-2, characterized in that the hydroformylation reaction mixture contains from 2 to 10 moles of monodentate phosphine per mole of multidentate phosphite ligand.

7. The process according to any of claims 1-2, characterized in that the hydroformylation reaction mixture contains from 1 to 1.2 moles of multidentate phosphite ligand per mole of rhodium or iridium.

8. A process according to any one of claims 1-2, characterized in that the multidentate organophosphite ligand has the general structure:wherein n is 2-6, X is an n-valent organic bridging group, R¹And R²Independently of one another, two organic monovalent aryl radicals and/or one divalent diaryl radical.

9. A process according to claim 8 characterised in that the multidentate phosphite ligand and rhodium or iridium form a chelate-type complex in the reaction zone.

10. A process according to claim 9 characterised in that the multidentate phosphite ligand is a bidentate phosphite ligand having the general structure:wherein Y and Z are identical or different organic radicals having at least 1 carbon atom, R¹And R²Are identical or different monovalent organic aryl radicals and/or a divalent diaryl radical.

11. The process according to claim 10, wherein Y and Z are of the formula-CO₂A carbonylalkoxy group of R wherein R is C₁-C₂₀Alkyl or C₆-C₁₂An aryl group.

12. The method according to claim 11, wherein R is¹And R²Are identical or different and contain at least 1R in the ortho position relative to the oxygen atom⁴Monovalent C of substitution of radicals₆-C₂₀Aryl radical, wherein R⁴Is C₁-C₂₀Alkyl or C₆-C₂₀Aryl, or R¹And R²Is a monovalent C having 2 or more rings₁₀-C₂₀Aromatic fused ring systems.

13. A process according to any one of claims 1-2, characterised in that the unsaturated organic compound is an internally unsaturated compound having 4-20 carbon atoms.

14. Process according to claim 13, characterized in that the organic compound is 3-pentenenitrile, 3-pentenoic acid or C of 3-pentenoic acid₁-C₆An alkyl ester.

15. Process according to claim 14, characterized in that the C of 3-pentenoic acid₁-C₆The alkyl ester is methyl 3-pentenoate or ethyl 3-pentenoate.

16. Process according to any of claims 1-2, characterized in that the aldehyde is prepared in a continuous process, wherein the catalyst system is reused in the process and fresh phosphine is added continuously or intermittently to the process according to claims 1-15.

17. A catalyst system comprising rhodium or iridium, a multidentate organophosphite ligand and a monodentate phosphine.

18. Catalyst system according to claim 17, characterized in that the steric hindrance parameter θ of the monodentate phosphine is 160-220 °.

19. Catalyst system according to any one of claims 17-18, characterized in that the steric hindrance parameter θ of the monodentate phosphine is 170 ° and 210 °.

20. Catalyst system according to any of claims 17 to 18, characterized in that the monodentate phosphine is tri (o-tolyl) phosphine.

21. Catalyst system according to any one of claims 17 to 18, characterized in that the metal is rhodium.

22. A catalyst system according to any one of claims 17 to 18 characterised in that from 1 to 40 moles of monodentate phosphine are present per mole of multidentate phosphite ligand.

23. A catalyst system according to any one of claims 17 to 18 characterised in that from 2 to 10 moles of monodentate phosphine are present per mole of multidentate phosphite ligand.

24. Catalyst system according to any of claims 17 to 18, characterized in that the multidentate phosphite ligand is a bidentate phosphite ligand according to any of claims 10 to 12.