Method for producing aldehyde, method for producing alcohol, and catalyst composition

Abstract

Provided is a method for producing an aldehyde, comprising causing an olefin to undergo a hydroformylation reaction, in the presence of a catalyst, with a gas which contains hydrogen and carbon monoxide, said method comprising extracting, from a reaction band, part or all of a reaction solution in which a high-boiling-point by-product has been accumulated, mixing a poor solvent for the catalyst into the extracted reaction solution in a mixing tank, precipitating aggregates which contain the catalyst and the high-boiling-point by-product, depositing the precipitated aggregates on the inner surface of the mixing tank, and recovering the aggregates.

Description

[Technical field]

[0001] The present invention relates to a method for producing an aldehyde and a method for producing an alcohol, and a catalyst composition. [Background technology]

[0002] A method for producing an aldehyde by hydroformylating an olefinically unsaturated organic compound with carbon monoxide and hydrogen in the presence of a long-form Group 8 to 10 metal-phosphine complex catalyst is well known as a method for producing an aldehyde. This hydroformylation reaction is also called the "oxo reaction." The mixed gas of hydrogen (H2) and carbon monoxide (CO) used in the reaction is called "oxo gas."

[0003] The catalyst used in the hydroformylation reaction of olefins contains expensive metals of Groups 8 to 10 of the periodic table such as rhodium, and therefore it is ideal to use the catalyst semi-permanently. Therefore, the usual method is to separate the reaction product from the reaction solution, and recycle the reaction solution containing the catalyst, which is the distillation residue, to the reaction zone for reuse, or to distill and separate the reaction product from the reaction zone by gas stripping, and continue the reaction while leaving the reaction solution containing the catalyst in the reaction zone.

[0004] In the hydroformylation reaction, high-boiling by-products such as aldehyde condensation by-products are generated and accumulated, so it is necessary to continuously or intermittently withdraw a part of the reaction liquid outside the reaction zone (the reaction zone is sometimes called the reaction system). Since the withdrawn reaction liquid contains the catalyst, particularly the expensive long-form Group 8 to 10 metals of the periodic table, in addition to the high-boiling by-products, it is extremely important to efficiently recover it from the standpoint of both economics and prevention of environmental pollution.

[0005] Patent Document 1 discloses a method in which a hydroformylation reaction liquid in which high-boiling by-products have accumulated after being extracted from a reaction zone is mixed with alcohol and water, contacted with hydrogen gas at 30°C, and then cooled to 0°C to crystallize and recover a rhodium-phosphine complex catalyst with hydrogen atoms coordinated thereto.

[0006] Patent Document 2 discloses a method in which an alcohol, water and hydrogen are mixed with a hydroformylation reaction liquid in which high-boiling by-products have accumulated after being extracted from a reaction zone, and the mixture is maintained at 10 to 30°C to precipitate and recover a rhodium-phosphine complex catalyst coordinated with hydrogen.

[0007] Patent Document 3 discloses a method for reactivating a deactivated catalyst by treating an alkylphosphine produced by partially substituting a ligand such as triarylphosphine with an alkyl group of an α-olefin with a sufficient amount of oxygen or an oxygen-containing gas at about 20 to 80° C. to convert it into the corresponding phosphine oxide.

[0008] Patent Document 4 discloses a method in which a hydroformylation reaction liquid in which high-boiling by-products have accumulated after being extracted from a reaction zone is mixed with alcohol and water, contacted with hydrogen gas at 30°C, and then cooled to 0°C to crystallize and recover a rhodium-phosphine complex catalyst with hydrogen atoms coordinated thereto. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] International Publication No. 2019-098242 [Patent Document 2] JP 2006-151826 A [Patent Document 3] Japanese Patent Application Publication No. 57-87845 [Patent Document 4] Japanese Patent Application Publication No. 57-122948 Summary of the Invention [Problem to be solved by the invention]

[0010] In the methods disclosed in Patent Documents 1 to 4, first, the rhodium-phosphine complex catalyst is crystallized in a state where high-boiling by-products are removed as much as possible, and then the recovered crystals are filtered to separate the crystals of the rhodium-phosphine complex catalyst from the crystallization mother liquid. In Patent Documents 1 to 4, the loss of the rhodium-phosphine complex catalyst in this filtration process is large, so that the rhodium-phosphine complex catalyst cannot be sufficiently recovered.

[0011] The present invention aims to solve these problems. An object of the present invention is to provide a method for producing an aldehyde, which is capable of recovering an expensive complex catalyst, particularly an expensive long-form metal of Groups 8 to 10 of the Periodic Table in the complex catalyst, from a hydroformylation reaction solution in high yield. Another object of the present invention is to provide a method for producing an alcohol, which comprises producing an aldehyde by the above-mentioned method for producing an aldehyde and then producing an alcohol from the aldehyde. Another object of the present invention is to provide a catalyst composition capable of recovering expensive complex catalysts used in reactions such as hydroformylation, particularly expensive long-form Group 8 to 10 metals of the periodic table in the complex catalyst, in high yield. [Means for solving the problem]

[0012] The present inventors have found that by mixing a poor solvent for the catalyst with the reaction liquid after the hydroformylation reaction, and subjecting the reaction liquid containing the catalyst and high-boiling by-products to an agglomeration treatment, and recovering the agglomerates as sticky agglomerates, the complex catalyst can be recovered in a higher yield than with conventional methods.

[0013] The invention was achieved based on these findings and is summarized as follows.

[0014] [1] A method for producing an aldehyde, comprising hydroformylating an olefin with a gas containing hydrogen and carbon monoxide in the presence of a catalyst, 1. A method for producing an aldehyde, comprising mixing a poor solvent for the catalyst with a part or all of the reaction liquid discharged from a reaction zone, thereby precipitating a sticky aggregate containing the catalyst.

[0015] [2] The method for producing an aldehyde according to [1], wherein a distribution ratio of high boiling point by-products contained in the coagulate is 4.0 mass% or more when the total mass of high boiling point by-products contained in the reaction liquid is 100 mass%.

[0016] [3] A method for producing an aldehyde according to [1] or [2], comprising mixing a poor solvent for the catalyst with a part or all of the reaction liquid in a mixing tank, and adhering the precipitated aggregate to an inner surface of the mixing tank, or precipitating the precipitated aggregate in an aggregated state within the mixing tank.

[0017] [4] A method for producing an aldehyde, comprising hydroformylating an olefin with a gas containing hydrogen and carbon monoxide in the presence of a catalyst, The method comprises mixing a poor solvent for the catalyst with a part or the whole of the reaction liquid discharged from the reaction zone to precipitate an aggregate containing the catalyst, A method for producing an aldehyde, wherein a distribution ratio of high boiling point by-products in the coagulate is 4.0 mass% or more when the total mass of the high boiling point by-products contained in the reaction liquid is 100 mass%.

[0018] [5] A method for producing an aldehyde according to [4], comprising mixing a poor solvent for the catalyst with a part or all of the reaction liquid in a mixing tank, and adhering the precipitated aggregate to an inner surface of the mixing tank, or precipitating the precipitate in an aggregated state within the mixing tank.

[0019] [6] A method for producing an aldehyde, comprising hydroformylating an olefin with a gas containing hydrogen and carbon monoxide in the presence of a catalyst, A part or all of the reaction liquid in which high boiling point by-products have accumulated is withdrawn from the reaction zone; The reaction liquid thus extracted is mixed with a poor solvent for the catalyst in a mixing tank to precipitate an aggregate containing the catalyst and the high-boiling by-products; and adhering the precipitated coagulate to an inner surface of the mixing tank and recovering the coagulate.

[0020] [7] The method for producing an aldehyde described in [6], wherein the aggregate has stickiness under the precipitation conditions.

[0021] [8] The method for producing an aldehyde according to [6] or [7], wherein a distribution ratio of high boiling point by-products in the coagulate is 4.0 mass% or more when the total mass of the high boiling point by-products contained in the extracted reaction liquid is 100 mass%.

[0022] [9] The method for producing an aldehyde according to any one of [1] to [8], wherein the precipitated coagulate is supplied to a hydroformylation reaction zone.

[0023]

[10] The method for producing an aldehyde according to [9], wherein the precipitated aggregate is dissolved in a good solvent for the catalyst and supplied to a hydroformylation reaction zone.

[0024]

[11] The method for producing an aldehyde according to any one of [1] to

[10] , wherein the precipitation is carried out under neutral to acidic conditions.

[0025]

[12] The method for producing an aldehyde according to any one of [1] to

[11] , wherein the catalyst is a long-form Group 8 to 10 metal-organophosphorus complex catalyst.

[0026]

[13] The method for producing an aldehyde according to

[12] , wherein the catalyst is a long-form Group 8 to 10 metal-phosphite complex catalyst.

[0027]

[14] The method for producing an aldehyde according to

[12] or

[13] , wherein the metal of Groups 8 to 10 of the long form periodic table is rhodium.

[0028]

[15] The method for producing an aldehyde according to any one of [1] to

[14] , wherein the poor solvent contains water and an alcohol.

[0029]

[16] The method for producing an aldehyde according to

[15] , wherein the poor solvent is a mixture of water and an alcohol, and the content of the water is 12 to 40 mass% with respect to 100 mass% of the total mass of the mixture.

[0030]

[17] The method for producing an aldehyde according to any one of [1] to

[16] , wherein the aggregate is precipitated under a temperature condition of 0° C. or higher and 70° C. or lower.

[0031]

[18] A method for producing an alcohol, comprising producing an aldehyde by the method according to any one of [1] to

[17] , and producing an alcohol from the aldehyde.

[0032]

[19] A catalyst composition comprising a catalyst and a high-boiling by-product, The catalyst is a long-form Group 8 to 10 metal-organophosphorus complex catalyst of the periodic table, A catalyst composition, wherein the content of the high-boiling by-products is 30 mass% or more, based on 100% by total mass of the catalyst composition.

[0033]

[20] The catalyst composition according to

[19] , wherein the catalyst composition has adhesive properties.

[0034]

[21] The catalyst composition according to

[19] or

[20] , wherein the catalyst is a catalyst for producing an aldehyde by hydroformylation of an olefin.

[0035]

[22] The catalyst composition according to any one of

[19] to

[21] , wherein the catalyst is a long-form Group 8 to 10 metal-phosphite complex catalyst of the periodic table.

[0036]

[23] The catalyst composition according to any one of

[19] to

[22] , wherein the long form metal of Groups 8 to 10 of the Periodic Table is rhodium.

[0037]

[24] Dissolving the catalyst composition according to any one of

[19] to

[23] in a good solvent for the catalyst to obtain a catalyst solution; and A method for producing an aldehyde, comprising subjecting an olefin to a hydroformylation reaction in the presence of the catalyst solution. Effect of the Invention

[0038] According to the present invention, it is possible to provide a method for producing an aldehyde, which is capable of recovering a complex catalyst, particularly an expensive metal of Groups 8 to 10 of the long form periodic table in the complex catalyst, from a hydroformylation reaction solution in high yield. The present invention also provides a method for producing an alcohol, which uses an aldehyde produced by the method for producing an aldehyde. Furthermore, according to the present invention, it is possible to provide a catalyst composition recovered in the above-mentioned method for producing an aldehyde. [Brief description of the drawings]

[0039] [Figure 1] FIG. 1 is a graph showing the relationship between the distribution rate of high-boiling by-products in the aggregates or crystallized products and the rhodium recovery rate in Examples 1 to 10 and Comparative Example 1. [Diagram 2] Fig. 2(a) is a photograph of the appearance of the mixing tank after flocculation obtained in Example 2, which shows an example of a state in which the flocculants adhere to the inner surface of the mixing tank and the reaction liquid after the reaction undergoes solid-liquid separation. Fig. 2(b) is a photograph of the appearance of the mixing tank after crystallization obtained in Comparative Example 1, which shows an example of a state in which the crystallized materials do not adhere to the inner surface of the mixing tank and the reaction liquid after the reaction does not undergo solid-liquid separation and forms a uniform slurry. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] The present invention will be described in detail below. The present invention is not limited to the following description, and can be modified in any manner without departing from the gist of the present invention.

[0041] Unless otherwise specified, in this specification, a numerical range expressed with "~" means a range including the numerical values ​​before and after "~" as the lower and upper limits. For example, "A~B" means A or more and B or less.

[0042] 1. Method for producing aldehydes A first embodiment of the method for producing an aldehyde of the present invention is a method for producing an aldehyde, comprising: subjecting an olefin to a hydroformylation reaction with a gas containing hydrogen and carbon monoxide in the presence of a catalyst (hereinafter, this step may be referred to as a "hydroformylation reaction step"); and comprising mixing a poor solvent for the catalyst with a part or all of the reaction liquid extracted from a reaction zone (hereinafter, this step may be referred to as a "reaction liquid extraction step") to precipitate a sticky aggregate containing the catalyst (hereinafter, this step may be referred to as an "aggregation step").

[0043] Furthermore, in the aldehyde production method of the first embodiment of the present invention, when the total mass of high boiling point by-products contained in the reaction liquid is 100 mass%, the distribution ratio of high boiling point by-products contained in the aggregate is preferably 4.0 mass% or more. Furthermore, in the method for producing an aldehyde according to the first embodiment of the present invention, a poor solvent for the catalyst is mixed with a part or all of the reaction liquid in a mixing tank, and the precipitated aggregate can be attached to the inner surface of the mixing tank, or can be precipitated in an aggregated state within the mixing tank.

[0044] A second embodiment of the method for producing an aldehyde of the present invention is a method for producing an aldehyde, comprising: subjecting an olefin to a hydroformylation reaction with a gas containing hydrogen and carbon monoxide in the presence of a catalyst (hereinafter, this step may be referred to as a "hydroformylation reaction step"); and mixing a poor solvent for the catalyst with a part or all of the reaction liquid extracted from a reaction zone (hereinafter, this step may be referred to as a "reaction liquid extraction step") to precipitate an aggregate containing the catalyst (hereinafter, this step may be referred to as an "aggregation step"), in which, when the total mass of the high-boiling by-products contained in the reaction liquid is taken as 100 mass%, the distribution ratio of the high-boiling by-products in the aggregate is 4.0 mass% or more.

[0045] Furthermore, in the method for producing an aldehyde according to the second embodiment of the present invention, a poor solvent for the catalyst is mixed with a part or all of the reaction liquid in a mixing tank, and the precipitated aggregate can be attached to the inner surface of the mixing tank, or can be precipitated in an aggregated state within the mixing tank.

[0046] A third embodiment of the method for producing an aldehyde of the present invention is a method for producing an aldehyde, comprising: subjecting an olefin to a hydroformylation reaction with a gas containing hydrogen and carbon monoxide in the presence of a catalyst (hereinafter, this step may be referred to as a "hydroformylation reaction step"); extracting a part or all of a reaction liquid in which high-boiling-point by-products have accumulated from a reaction zone (hereinafter, this step may be referred to as a "reaction liquid extraction step"); mixing a poor solvent for the catalyst with the extracted reaction liquid in a mixing tank to precipitate an aggregate containing the catalyst and the high-boiling-point by-products (hereinafter, this step may be referred to as an "aggregation step"); and adhering the precipitated aggregate to an inner surface of the mixing tank and recovering it (hereinafter, this step may be referred to as a "recovery step").

[0047] In the present invention, when a poor solvent for the catalyst is mixed with the reaction liquid extracted from the hydroformylation reaction zone, a sticky precipitate containing the catalyst and high-boiling by-products is precipitated, as shown in the examples described later. Since this precipitate is sticky and not in a crystalline state, it cannot be adequately described as a "crystallized product." Therefore, in the present invention, this precipitate is called an "aggregate" to distinguish it from the non-sticky precipitates precipitated in the conventional method and the comparative example described later. On the other hand, the non-sticky precipitates in the conventional method and the comparative example described later are called "crystallized products." As described above, the tank in which the reaction liquid and the poor solvent for the catalyst are mixed is called a "mixing tank," and "precipitating" the "aggregate" in this "mixing tank" is called an "aggregation treatment," and this process is called an "aggregation process." In contrast, "precipitating" a "crystallized product" as in the conventional method and the comparative example described below is called a "crystallization treatment."

[0048] In this specification, the "internal surface of the mixing tank" refers to a portion in the mixing tank where the flow of the reaction liquid is slow, a portion against which aggregates of the reaction liquid are pressed during stirring, or a portion having the shape of a protrusion in the mixing tank. Specific examples of the surface of the mixing tank include the bottom surface and inner wall, baffles, stirring blades and shaft, and the surface of the side tube. In addition, in this specification, the terms "reaction zone" and "hydroformylation reaction zone" refer to a zone including a reactor for carrying out a hydroformylation reaction and peripheral equipment for the reactor, such as a gas-liquid separator, associated with the reactor.

[0049] The catalyst composition of the present invention is a catalyst composition comprising a catalyst and high-boiling by-products, wherein the catalyst is a long-form Group 8 to 10 metal-organophosphorus complex catalyst of the periodic table, and the content of the high-boiling by-products is 30 mass% or more, relative to 100% by total mass of the catalyst composition.

[0050] First, the hydroformylation reaction according to the first, second and third embodiments of the aldehyde production method of the present invention (hereinafter, these may be collectively referred to as "the present invention") will be described, and then the reaction liquid withdrawal step, the flocculation step and the recovery step will be described for each step.

[0051] [Hydroformylation reaction] [catalyst] In the present invention, the catalyst used in the hydroformylation reaction is not particularly limited as long as it has a catalytic effect on the hydroformylation reaction of olefins. As the catalyst used in the hydroformylation reaction, it is preferable to use a long-form Group 8 to 10 metal of the periodic table (hereinafter referred to as "Group 8 to 10 metal")-organophosphorus complex catalyst, because of its excellent reaction activity.

[0052] In the present invention, the Group 8 to 10 metals are metals that belong to Groups 8 to 10 of the long-form periodic table. Among them, ruthenium, cobalt, rhodium, palladium, and platinum are preferred because of their high activity when used as catalysts, and rhodium is particularly preferred because of its high activity.

[0053] As the organophosphorus ligand compound for forming the Group 8 to 10 metal-organophosphorus complex catalyst, any trivalent organophosphorus compound commonly used to function as a monodentate or polydentate ligand for a Group 8 to 10 metal can be used. Among these, an example of the organophosphorus compound serving as a monodentate ligand is a tertiary triorganophosphine represented by the following formula (I).

[0054] [ka]

[0055] (In formula (I), each R independently represents a substituted or unsubstituted monovalent hydrocarbon group.)

[0056] Examples of the monovalent hydrocarbon group represented by R include an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, an aryl group having 3 to 12 carbon atoms, an alkylaryl group having 6 to 24 carbon atoms, and an arylalkyl group having 6 to 24 carbon atoms. That is, the above-mentioned triorganophosphine is, for example, a trialkylphosphine, a triarylphosphine, a tricycloalkylphosphine, an alkylarylphosphine, a cycloalkylarylphosphine, and an alkylcycloalkylphosphine.

[0057] Substituents that the monovalent hydrocarbon group may have include, but are not limited to, alkyl groups, alkoxy groups, and the like.

[0058] Specific examples of triorganophosphines include tributylphosphine, trioctylphosphine, triphenylphosphine, tritolylphosphine, tricycloalkylphosphine, monobutyldiphenylphosphine, dipropylphenylphosphine, cyclohexyldiphenylphosphine, etc. Among these, triphenylphosphine is preferred because it is chemically stable due to its low activity and is easily available.

[0059] Other examples of the trivalent organic phosphorus compound that can be used include trivalent phosphite compounds represented by the following formulas (1) to (10).

[0060] <Trivalent phosphite compound represented by formula (1)> [ka]

[0061] (In formula (1), R 1 ~R 3 each independently represents a monovalent hydrocarbon group which may have a substituent.

[0062] R 1 ~R 3 Examples of the monovalent hydrocarbon group represented by the formula (1) which may have a substituent include an alkyl group, an aryl group, and a cycloalkyl group.

[0063] Specific examples of the compound represented by formula (1) include trialkyl phosphites such as trimethyl phosphite, triethyl phosphite, n-butyl diethyl phosphite, tri-n-butyl phosphite, tri-n-propyl phosphite, tri-n-octyl phosphite, and tri-n-dodecyl phosphite; triaryl phosphites such as triphenyl phosphite and trinaphthyl phosphite; and alkylaryl phosphites such as dimethylphenyl phosphite, diethylphenyl phosphite, and ethyldiphenyl phosphite. In addition, bis(3,6,8-tri-t-butyl-2-naphthyl)phenyl phosphite and bis(3,6,8-tri-t-butyl-2-naphthyl)(4-biphenyl)phenyl phosphite described in JP-A-6-122642 may be used. Among these, triphenyl phosphite is the most preferable.

[0064] <Trivalent phosphite compound represented by formula (2)> [ka]

[0065] (In formula (2), R 4 R represents a divalent hydrocarbon group which may have a substituent. 5 represents a monovalent hydrocarbon group which may have a substituent.

[0066] R 4 Examples of the divalent hydrocarbon group which may have a substituent include an alkylene group which may contain an oxygen, nitrogen, sulfur atom, etc. in the middle of the carbon chain; a cycloalkylene group which may contain an oxygen, nitrogen, sulfur atom, etc. in the middle of the carbon chain; a divalent aromatic group such as phenylene and naphthylene; a divalent aromatic group in which a divalent aromatic ring is bonded directly or via an alkylene group or an atom such as oxygen, nitrogen or sulfur; and a divalent aromatic group and an alkylene group bonded directly or via an atom such as oxygen, nitrogen or sulfur.

[0067] R 5 Examples of the monovalent hydrocarbon group include an alkyl group, an aryl group, and a cycloalkyl group.

[0068] Examples of the compound represented by formula (2) include the compounds described in US Pat. No. 3,415,906, such as neopentyl (2,4,6-t-butyl-phenyl) phosphite and ethylene (2,4,6-t-butyl-phenyl) phosphite.

[0069] <Trivalent phosphite compound represented by formula (3)> [ka]

[0070] (In formula (3), R 10 is R in the above formula (2) 5 Synonymous with Ar 1 and Ar 2 Each of x and y independently represents an aryl group which may have a substituent. Each of Q and y independently represents 0 or 1. Q is -CR 11 R 12 -, -O-, -S-, -NR13 -, -SiR 14 R 15 and -CO-. 11 and R 12 R each independently represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, a phenyl group, a tolyl group, or an anisyl group. 13 , R 14 and R 15 each independently represents a hydrogen atom or a methyl group; and n represents 0 or 1.

[0071] Specific examples of the trivalent phosphite compound represented by formula (3) include compounds described in U.S. Pat. No. 4,599,206, such as 1,1'-biphenyl-2,2'-diyl-(2,6-di-t-butyl-4-methylphenyl) phosphite, and compounds described in U.S. Pat. No. 4,717,775, such as 3,3'-di-t-butyl-5,5'-dimethoxy-1,1'-biphenyl-2,2'-diyl(2-t-butyl-4-methoxyphenyl) phosphite.

[0072] <Trivalent phosphite compound represented by formula (4)> [ka]

[0073] (In formula (4), R 6 represents a trivalent hydrocarbon group which may have a cyclic or acyclic substituent.

[0074] Examples of the compound represented by formula (4) include compounds described in US Pat. No. 4,567,306, such as 4-ethyl-2,6,7-trioxa-1-phosphabicyclo-[2,2,2]-octane.

[0075] <Trivalent phosphite compounds represented by formulas (5) and (6)> [ka]

[0076] (In formula (5), R 7 is R in the above formula (3). 4 Synonymous with R. 8 and R 9 each independently represents a hydrocarbon group which may have a substituent. a and b each represent an integer of 0 to 6. The sum of a and b is 2 to 6. X represents a hydrocarbon group having a valence of (a+b).

[0077] Among the compounds represented by formula (5), preferred examples include compounds represented by the following formula (6): Also included are the compounds described in JP-A-62-116535 and JP-A-62-116587.

[0078] [ka]

[0079] (In formula (6), X is alkylene, arylene, or -Ar 1 -(CH2)x-Qn-(CH2)y-Ar 2 - represents a divalent group selected from the group consisting of Ar 1 , Ar 2 , Q, x, y, and n are Ar in the above formula (3). 1 , Ar 2 , Q, x, y, n.)

[0080] <Trivalent phosphite compound represented by formula (7)> [ka]

[0081] (In formula (7), X, Ar 1 , Ar 2 , Q, x, y, and n are X, Ar in the above formula (3). 1 , Ar 2 , Q, x, y, n. 18 is R in the above formula (2) 4 is equivalent to

[0082] <Trivalent phosphite compound represented by formula (8)> [ka]

[0083] (In formula (8), R 19 and R 20 each independently represents an aromatic hydrocarbon group, and at least one of the aromatic hydrocarbon groups has a hydrocarbon group on a carbon atom adjacent to a carbon atom to which an oxygen atom is bonded. m represents an integer of 2 to 4. 19 )(OR 20 ) groups may be different from each other. X represents an m-valent hydrocarbon group which may have a substituent.

[0084] Of the compounds represented by formula (8), for example, the compounds described in JP-A-5-178779 are preferred.

[0085] <Trivalent phosphite compound represented by formula (9)> [ka]

[0086] (In formula (9), R 21 ~R 24 R each independently represents a hydrocarbon group which may have a substituent. 21 and R 22 , R 23 and R 24 may be bonded to each other to form a ring. W represents a divalent aromatic hydrocarbon group which may have a substituent. L represents a saturated or unsaturated divalent aliphatic hydrocarbon group which may have a substituent.

[0087] As the compound represented by formula (9), for example, the compound described in JP-A-8-259578 can be used.

[0088] <Trivalent phosphite compound represented by formula (10)> [ka]

[0089] (In formula (10), R 25 ~R 28 R represents a monovalent hydrocarbon group which may have a substituent. 25 and R 26 , R 27 and R 28 may be bonded to each other to form a ring. A and B each independently represent a divalent hydrocarbon group which may have a substituent. n represents an integer of 0 or 1.

[0090] R 25 ~R 28 Examples of the monovalent hydrocarbon group represented by the formula (1) and which may have a substituent include an alkyl group, an aryl group, a cycloalkyl group, etc. The divalent hydrocarbon group represented by A and B and which may have a substituent may be any of aromatic, aliphatic, and alicyclic.

[0091] <Bisphosphite compound represented by formula (11)> [ka]

[0092] In formula (11), R 31 and R 41 each independently represents a group selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, and a cycloalkyl group having 3 to 20 carbon atoms.

[0093] Examples of the alkyl group having 1 to 20 carbon atoms include linear or branched alkyl groups such as methyl, ethyl, n-propyl, i-propyl, s-butyl, t-butyl, isopentyl, neopentyl, t-pentyl, t-hexyl, and 1,1,2-trimethylpropyl. Among them, those having 3 to 20 carbon atoms are preferred, those having 4 to 20 carbon atoms are more preferred, and those having 4 to 10 carbon atoms are particularly preferred. Furthermore, those in which the carbon atom bonded to the aromatic ring is tertiary are preferred, and examples thereof include t-butyl, t-pentyl, and t-hexyl groups.

[0094] Examples of the cycloalkyl group having 3 to 20 carbon atoms include a cyclohexyl group, a cyclooctyl group, an adamantyl group, etc. Among these, a cycloalkyl group having 6 to 14 carbon atoms is preferred, and a cycloalkyl group having 6 to 10 carbon atoms is more preferred.

[0095] R 31 and R 41 R is preferably a tertiary alkyl group having 4 to 20 carbon atoms, more preferably a tertiary alkyl group having 4 to 7 carbon atoms, and particularly preferably a t-butyl group. 31 and R 41 may be the same or different.

[0096] R 31 and R 41 If R is a t-butyl group, the bulkiness of the t-butyl group provides a sufficient stabilizing effect against hydrolysis of the compound represented by formula (11). 31 and R 41 is particularly preferably a t-butyl group.

[0097] R 32 and R 42each independently represents a group selected from the group consisting of a hydrogen atom, an alkyl group and an alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group and a cycloalkoxy group having 3 to 20 carbon atoms, a dialkylamino group having 2 to 20 carbon atoms, an aryl group and an aryloxy group having 6 to 20 carbon atoms, an alkylaryl group, an alkylaryloxy group, an arylalkyl group and an arylalkoxy group having 7 to 20 carbon atoms, a cyano group, a hydroxy group, and a halogen atom.

[0098] Examples of the alkyl group having 1 to 20 carbon atoms include linear or branched alkyl groups such as methyl, ethyl, n-propyl, i-propyl, n-butyl, s-butyl, t-butyl, n-pentyl, isopentyl, neopentyl, t-pentyl, and t-hexyl. Examples of the cycloalkyl group having 3 to 20 carbon atoms include a cyclohexyl group, a cyclooctyl group, and an adamantyl group.

[0099] Examples of alkoxy groups having 1 to 20 carbon atoms include a methoxy group, an ethoxy group, an isopropoxy group, a t-butoxy group, etc. Among these, an alkoxy group having 1 to 12 carbon atoms is preferred. Examples of the cycloalkoxy group having 3 to 20 carbon atoms include a cyclopentyloxy group.

[0100] Examples of the dialkylamino group having 2 to 20 carbon atoms include a dimethylamino group and a diethylamino group. Examples of the aryl group having 6 to 20 carbon atoms include a phenyl group and a naphthyl group. Examples of the aryloxy group having 6 to 20 carbon atoms include a phenoxy group and a naphthoxy group. Examples of the alkylaryl group having 7 to 20 carbon atoms include a p-tolyl group and an o-tolyl group.

[0101] Examples of the alkylaryloxy group having 7 to 20 carbon atoms include 2,3-xylenoxy. An example of the arylalkyl group having 7 to 20 carbon atoms is a benzyl group. Examples of the arylalkoxy group having 7 to 20 carbon atoms include a 2-(2-naphthyl)ethoxy group. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0102] R 32 and R 42 is preferably a hydrogen atom. A substituent at this position has little effect on improving the reactivity in the hydroformylation reaction or on stabilizing the compound represented by formula (11) itself. Therefore, from the viewpoint of reducing the production cost of the compound, a hydrogen atom, which is the simplest substituent, is preferred.

[0103] R 33 and R 43 each independently represents a group selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, and an alkylaryl group and arylalkyl group having 7 to 20 carbon atoms.

[0104] Examples of alkyl groups having 1 to 20 carbon atoms include linear or branched alkyl groups such as methyl, ethyl, n-propyl, i-propyl, s-butyl, t-butyl, isopentyl, neopentyl, t-pentyl, and t-hexyl. Among these, alkyl groups having 4 to 20 carbon atoms are preferred, and alkyl groups having 4 to 10 carbon atoms are particularly preferred. Furthermore, alkyl groups in which the carbon atom bonded to the aromatic ring is tertiary are preferred, and examples thereof include t-butyl, t-pentyl, and t-hexyl groups.

[0105] Examples of the cycloalkyl group having 3 to 20 carbon atoms include a cyclohexyl group, a cyclooctyl group, an adamantyl group, etc. Among these, a cycloalkyl group having 6 to 14 carbon atoms is preferred, and a cycloalkyl group having 6 to 10 carbon atoms is more preferred. Examples of the aryl group having 6 to 20 carbon atoms include a phenyl group and a naphthyl group. Examples of the alkylaryl group having 7 to 20 carbon atoms include a p-tolyl group and an o-tolyl group. An example of the arylalkyl group having 7 to 20 carbon atoms is a benzyl group.

[0106] R 33 and R 43 are each independently preferably a tertiary alkyl group having 4 to 20 carbon atoms, more preferably a tertiary alkyl group having 4 to 7 carbon atoms, and particularly preferably a t-butyl group.

[0107] R 34 and R 44 each independently represents a group selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, a silyl group, a siloxy group, and a halogen atom.

[0108] Examples of the alkyl group having 1 to 12 carbon atoms include linear or branched alkyl groups such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a t-butyl group, and a decyl group. Examples of the cycloalkyl group having 3 to 12 carbon atoms include a cyclopropyl group and a cyclohexyl group. Examples of the alkoxy group having 1 to 12 carbon atoms include a methoxy group, an ethoxy group, and a t-butoxy group.

[0109] An example of the silyl group is a trimethylsilyl group. Examples of the siloxy group include a silyl group and a trimethylsiloxy group. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0110] Of these, R 34 and R 44 are each independently preferably an alkyl group having 1 to 3 carbon atoms, such as a methyl group or an ethyl group, an alkoxy group having 1 to 3 carbon atoms, such as a methoxy group or an ethoxy group, or a halogen atom, more preferably an alkyl group having 1 to 3 carbon atoms; R 34 and R 44 It is particularly preferred that is a methyl group.

[0111] R 34 and R 44 As the alkyl group, a small group such as an alkyl group having 1 to 3 carbon atoms, particularly a methyl group, is preferred, because it allows the hydroformylation reaction to proceed smoothly while improving the stability of the compound represented by formula (11).

[0112] Z 1 ~Z 4 are each independently an aryl group having 6 to 20 carbon atoms. The aryl group may have a substituent. 1 and Z 2 and Z 3 and Z 4 None of the are bonded to each other.

[0113] In particular, Z 1 ~Z 4 is preferably one that does not have a substituent on an aromatic ring carbon atom adjacent to the carbon atom bonded to an oxygen atom, or, even if the aromatic ring carbon atom has a substituent, the substituent has 0 to 2 carbon atoms.

[0114] Z 1 ~Z 4has a substituent on an aromatic ring carbon atom adjacent to the carbon atom bonded to the oxygen atom, the substituent is preferably selected from the group consisting of groups having 1 to 2 carbon atoms, such as a methyl group and an ethyl group, a trifluoromethyl group, a cyano group, a nitro group, and halogen atoms, such as a chlorine atom and a fluorine atom.

[0115] Z 1 ~Z 4 When Z has a substituent at a position other than the aromatic ring carbon atom, the substituent may be a straight or branched alkyl group having 1 to 12 carbon atoms, preferably 1 to 8 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an s-butyl group, a t-butyl group, an n-pentyl group, an isopentyl group, a neopentyl group, or a t-pentyl group; an alkoxy group having 1 to 12 carbon atoms, preferably 1 to 8 carbon atoms, such as a methoxy group or an ethoxy group; or an aryl group having 6 to 18 carbon atoms, preferably 6 to 10 carbon atoms, such as a phenyl group or a naphthyl group. Other examples of the substituent include a halogen atom, a cyano group, a nitro group, a trifluoromethyl group, a hydroxyl group, an amino group, an acyl group, a carbonyloxy group, an oxycarbonyl group, an amido group, a sulfonyl group, a sulfinyl group, a silyl group, and a thionyl group. 1 ~Z 4 may each have 1 to 5 of these substituents.

[0116] Z 1 ~Z 4Preferred examples of the aryl group include a phenyl group, a 1-naphthyl group, a 2-naphthyl group, a p-trifluoromethylphenyl group, a 2-ethylphenyl group, a 2-methylphenyl group, a 3-methylphenyl group, a 4-methylphenyl group, a 2,3-dimethylphenyl group, a 2,4-dimethylphenyl group, a 2,5-dimethylphenyl group, a 3,4-dimethylphenyl group, a 3,5-dimethylphenyl group, a 2-chlorophenyl group, a 3-chlorophenyl group, a 4-chlorophenyl group, a 2,3-dichlorophenyl group, a 2,4-dichlorophenyl group, a 2,5-dichlorophenyl group, a 3,4-dichlorophenyl group, Examples of such groups include a chlorophenyl group, a 3,5-dichlorophenyl group, a 2-methoxyphenyl group, a 3-methoxyphenyl group, a 4-methoxyphenyl group, a 2,3-dimethoxyphenyl group, a 3,4-dimethoxyphenyl group, a 3,5-dimethoxyphenyl group, a 4-cyanophenyl group, a 4-nitrophenyl group, a 4-phenylphenyl group, a 5,6,7,8-tetrahydro-1-naphthyl group, a 5,6,7,8-tetrahydro-2-naphthyl group, a 2-methyl-1-naphthyl group, a 4-chloro-1-naphthyl group, a 2-nitro-1-naphthyl group, and a 7-methoxy-2-naphthyl group.

[0117] Among these, a 1-naphthyl group or a 2-naphthyl group is preferred from the viewpoints of improving the thermal stability of the ligand and improving the selectivity for the production of straight-chain aldehydes when aldehydes are produced by a hydroformylation reaction.

[0118] The bisphosphite compound represented by formula (11) is 31 and R 41 are each independently a tertiary alkyl group having 4 to 20 carbon atoms; R 32 and R 42 is a hydrogen atom, and R 33 and R 43 are each independently a tertiary alkyl group having 4 to 20 carbon atoms, and R 34 and R 44 are each independently selected from the group consisting of an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, and a halogen atom. 1~Z 4 each independently has no substituent on an aromatic ring carbon atom adjacent to the carbon atom bonded to the oxygen atom, or has a substituent having 1 to 2 carbon atoms on the aromatic ring carbon atom; and Z 1 ~Z 4 Preferred are bisphosphite compounds in which none of the above are bonded to each other.

[0119] Further, the bisphosphite compound represented by the formula (11) is 31 , R 41 , R 33 and R 43 are each independently a tertiary alkyl group having 4 to 7 carbon atoms; R 32 and R 42 is a hydrogen atom, and R 34 and R 44 However, bisphosphite compounds in which each of the groups is independently an alkyl group having 1 to 3 carbon atoms are more preferred. 1 ~Z 4 are more preferably bisphosphite compounds in which each independently represents a 1-naphthyl group or a 2-naphthyl group, and R 31 , R 41 , R 33 and R 43 is a t-butyl group, and R 34 and R 44 Particularly preferred are bisphosphite compounds in which is a methyl group.

[0120] Examples of the bisphosphite compound represented by the above formula (11) are shown below. The symbols in the following formulas have the following meanings.

[0121] [ka]

[0122] [ka]

[0123] [ka]

[0124]

change

[0125]

change

[0126]

change

[0127]

change

[0128]

change

[0129]

change

[0130]

change

[0131]

change

[0132]

change

[0133]

change

[0134] [ka]

[0135] [ka]

[0136] The bisphosphite compound represented by formula (11) can be produced by the method described in WO 2019 / 039565.

[0137] These organophosphorus ligand compounds may be used alone or in combination of two or more, but usually only one is used.

[0138] The organic phosphorus ligand compound is not particularly limited, but from the viewpoint of excellent catalytic reaction activity in the hydroformylation reaction and thermal decomposition resistance, the phosphite compound represented by the formula (10) or the bisphosphite compound represented by the formula (11) is preferred, and the bisphosphite compound represented by the formula (11) is particularly preferred. That is, the Group 8 to 10 metal-organophosphorus complex catalyst used in the present invention is preferably a Group 8 to 10 metal-phosphite complex catalyst.

[0139] The Group 8 to 10 metal-organic phosphorus complex catalyst can be easily prepared from a long-form Group 8 to 10 metal compound of the periodic table (hereinafter referred to as "Group 8 to 10 metal compound") and an organic phosphorus ligand compound by a known complex formation method. The Group 8 to 10 metal compound and the organic phosphorus ligand compound may be supplied to a reaction zone to form a complex in the reaction zone. In this case, the organic phosphorus ligand compound may be introduced into the reaction zone as it is, but considering ease of handling, it is preferable to introduce it after dissolving it in the reaction medium.

[0140] Examples of the Group 8 to 10 metal compounds include water-soluble inorganic salts or inorganic complex compounds such as rhodium chloride, palladium chloride, ruthenium chloride, platinum chloride, rhodium bromide, rhodium iodide, rhodium sulfate, rhodium nitrate, palladium nitrate, rhodium ammonium chloride, and sodium rhodium chloride; water-soluble organic acid salts such as rhodium formate, rhodium acetate, palladium acetate, rhodium propionate, palladium propionate, and rhodium octanoate; and the like. Also, complex species of each metal may be used. Among them, it is preferable to use rhodium acetate from the viewpoint of excellent reaction activity and catalyst cost.

[0141] [Hydroformylation reaction process] The hydroformylation reaction is carried out by reacting an olefin with hydrogen and carbon monoxide in the presence of a catalyst such as a Group 8 to 10 metal-organophosphorus complex catalyst. The olefin is not particularly limited, and examples thereof include olefins having a carbon number of 2 to 20. Examples of the olefins having a carbon number of 2 to 20 include α-olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, and 1-octene, and internal olefins such as 2-butene, 2-pentene, 3-hexene, and 4-octene.

[0142] The reaction medium for the hydroformylation reaction is preferably a solvent that dissolves the raw material olefin and the catalyst such as a Group 8 to 10 metal-organic phosphorus complex catalyst, has a higher boiling point than the aldehyde produced, and does not inhibit the reaction. Examples of solvents that can be used in the hydroformylation reaction include aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as hexane and octane; esters such as butyl acetate and butyl butyrate; and ketones.

[0143] The concentration of the catalyst in the reaction medium is usually 1 ppm by mass to 10% by mass in terms of metal atoms such as Group 8 to 10 metals, and an excess amount of an organophosphorus ligand compound such as a phosphite compound used as a ligand is usually present in the reaction medium in order to increase the stability of the complex catalyst, etc.

[0144] The hydroformylation reaction can be carried out under known conditions. For example, when a Group 8 to 10 metal-organophosphorus complex catalyst, particularly a rhodium-phosphite complex catalyst, is used, the reaction conditions are usually appropriately selected within the following ranges. Hydrogen partial pressure: 0.01 to 20 MPaG Carbon monoxide partial pressure: 0.01 to 20 MPaG Total pressure: 0.02MPaG~30MPaG Hydrogen partial pressure / carbon monoxide partial pressure: 0.1 to 10 Reaction temperature: 60~200℃ Rh (rhodium) concentration: several ppm to several percent by mass P (free organic phosphorus ligand) / Rh: 2-10,000 (molar ratio) Reaction time: several minutes to several tens of hours

[0145] In the hydroformylation reaction, an aldehyde having a carbon number of n+1 can be obtained from a raw material olefin having a carbon number of n (n is, for example, an integer of 2 to 20). Examples of such aldehydes include propionaldehyde, butylaldehyde, pentylaldehyde, hexylaldehyde, heptylaldehyde, octylaldehyde, nonylaldehyde, and decylaldehyde. In general, the aldehyde is obtained as a mixture of linear and branched aldehydes.

[0146] The hydroformylation reaction is usually carried out under the above reaction conditions using a flow reactor, but a batch reactor can also be used.

[0147] The main types of flow reaction (reaction using the above-mentioned flow reactor) are the stripping method and the liquid circulation method.

[0148] The stripping method is a method in which a reaction liquid containing a catalyst is held in a reactor, an olefin and an oxo gas are continuously supplied, and the aldehyde produced by the reaction is vaporized in the reactor and removed from the system.

[0149] The liquid circulation system is a method in which a reaction medium containing an olefin, an oxo gas, and a catalyst is continuously supplied to a reactor, and a reaction liquid containing the produced aldehyde, the catalyst, the reaction medium, etc. is continuously withdrawn from the reactor. The reaction liquid withdrawn from the reactor is separated into the produced aldehyde and a reaction liquid containing the catalyst by a separation operation such as stripping with unreacted gas or distillation. The resulting produced aldehyde is withdrawn from the system, and the reaction liquid containing the catalyst (in the present invention, this reaction liquid corresponds to the reaction liquid withdrawn in the reaction liquid withdrawal step) is withdrawn from the system. ) is usually recycled by being returned to the reactor after high-boiling by-products in the reaction liquid are removed by a known separation operation such as distillation. In the present invention, in the aggregation step described below, the content of high-boiling by-products in the reaction liquid can be adjusted to control the stickiness of the resulting aggregate.

[0150] In the case of the stripping method, high-boiling by-products, which are by-products of the hydroformylation reaction, accumulate in the reaction liquid containing the catalyst held in the reactor, and therefore, usually, a part of the reaction liquid containing the high-boiling by-products and the catalyst (in the present invention, this reaction liquid corresponds to the reaction liquid withdrawn in the reaction liquid withdrawing step) is intermittently withdrawn from the reaction zone. In the case of the liquid circulation method, if the reaction liquid containing the catalyst is continuously recycled, high-boiling by-products accumulate in the reaction zone. Therefore, a part of the reaction liquid containing the high-boiling by-products and the catalyst (in the present invention, this reaction liquid corresponds to the reaction liquid withdrawn in the reaction liquid withdrawal step) is withdrawn continuously or intermittently from the reaction zone. The amount of the reaction liquid discharged from the reaction zone, i.e., the reactor, may be appropriately determined depending on the amount of high-boiling by-products produced.

[0151] Usually, when the reaction solution is withdrawn from the reaction zone, a catalyst is newly supplied to the reaction zone in an amount corresponding to the catalyst contained in the withdrawn reaction solution. In the present invention, the amount of catalyst newly supplied can be reduced by subjecting the withdrawn reaction solution to a coagulation process and returning it to the reaction zone. In particular, the reaction can be maintained with almost no replenishment of Group 8 to 10 metals.

[0152] The components of the high-boiling by-products are diverse and complex, but they are mainly aldehyde condensates produced by condensation of the aldehyde, which is the target product of the hydroformylation reaction, and have a higher boiling point than the produced aldehyde, and are high-boiling substances that cannot be removed by a simple distillation process of the aldehyde.Specific examples of such high-boiling by-products include aldols, which are dimers of the produced aldehyde, ester compounds, which are dimers of the produced aldehyde and are produced by the Tishchenko reaction of the produced aldehyde, unsaturated aldehydes, which are dehydration products of the aldol, saturated aldehydes and saturated alcohols, which are hydrogenation products of the unsaturated aldehyde, unsaturated ethers, which are dehydration products of hemiacetals obtained by reacting the produced aldehyde with alcohols, which are hydrogenated products of the produced aldehyde, acetals obtained by reacting the hemiacetals with the produced aldehyde, and trimers of the produced aldehyde.

[0153] When a Group 8 to 10 metal-phosphite complex catalyst is used as the catalyst, the reaction liquid in which the above-mentioned high-boiling by-products have accumulated contains phosphite, phosphonate produced by decomposition of the phosphite, phosphorous acid, and the like.

[0154] Taking the example of using rhodium as the Group 8 to 10 metal, the following rhodium complexes (a) and (b) are present in the reaction liquid in which the above-mentioned high-boiling by-products have accumulated. (a) Complexes in which rhodium (Rh) is coordinated with carbon monoxide and a bisphosphite represented by the above formula (11): for example, RhH(CO)2 (bisphosphite) and RhH(CO) (bisphosphite) (b) Rhodium cluster complexes in which multiple rhodium atoms are bonded to which carbon monoxide and the bisphosphite represented by the above formula (11) are coordinated: for example, [Rh(CO)(bisphosphite)]2 or [Rh(CO)2(bisphosphite)]2 Although rhodium has been used as an example in the above explanation, the same applies to other Group 8 to 10 metals.

[0155] [Reaction solution withdrawal process] The reaction liquid withdrawal step is a step of withdrawing a part or the whole of the reaction liquid in which high-boiling by-products have accumulated from the hydroformylation reaction zone. Specifically, it is a step of withdrawing a reaction liquid containing an aldehyde produced by the hydroformylation reaction, a catalyst, a reaction medium, etc., from the reactor while carrying out the hydroformylation reaction as described above.

[0156] The reaction liquid in the hydroformylation reaction zone contains about 40 to 80 mass% of high-boiling by-products. In the aggregation step, a poor solvent for the catalyst is added to and mixed with the reaction liquid containing the high-boiling by-products to crystallize an aggregate containing the catalyst and the high-boiling by-products. As disclosed in the above-mentioned Patent Documents 1 to 4, this eliminates the loss of the catalyst in the filtration process and allows the catalyst to be recovered at a high recovery rate, compared to the method of performing crystallization in a state where the high-boiling by-products are removed as much as possible, filtering the precipitated crystals, and separating the catalyst crystals from the crystallization mother liquor.

[0157] In the reaction liquid withdrawing step, the hydroformylation reaction liquid withdrawn from the hydroformylation reaction zone may be fed to the coagulation step after removing light boiling components therefrom, if necessary. In order to remove the light boiling components from the reaction liquid, a known separation operation such as distillation can be used.

[0158] When a rhodium-phosphite complex catalyst is used as the catalyst, the reaction liquid extracted in the reaction liquid extraction step, i.e., the reaction liquid before the coagulation treatment, usually has the following composition, and this reaction liquid is subjected to the next coagulation step.

[0159] (Composition of the reaction solution withdrawn in the reaction solution withdrawal step) Rhodium atoms in complex catalyst: 50 to 2000 mass ppm Phosphite compounds: 1000 mass ppm to 3 mass % n-Aldehyde: 1 to 30% by mass Other components (various complexes, high boiling point by-products, etc.): 40 to 80% by mass

[0160] The "various complexes" contained in the "other components" refer to the various rhodium complexes contained in the reaction liquid in which high-boiling by-products have accumulated, as described above in the section [Hydroformylation Reaction Step].

[0161] [Agglutination process] In the flocculation step, a poor solvent for the catalyst (hereinafter sometimes simply referred to as "poor solvent") is added to and mixed with the reaction liquid extracted in the reaction liquid extraction step to precipitate flocculates containing the catalyst and high-boiling by-products.

[0162] Specifically, the withdrawn reaction liquid and poor solvent are charged into a mixing tank to precipitate the aggregates.

[0163] The poor solvent is one in which the solubility of the Group 8 to 10 metal compound is lower than that of the reaction liquid. The poor solvent is preferably one that maintains a homogeneous phase with the reaction liquid and is not involved in the reaction in the reaction zone.

[0164] Specific examples of poor solvents include methanol, ethanol, propanol (n-, i-), butanol (n-, i-, t-), acetone, and mixtures of these with water. From the viewpoint of the recovery rate of the Group 8 to 10 metal-phosphite complex catalyst, a mixture of water and an alcohol is preferred, and a mixture of water and an alcohol having 1 to 3 carbon atoms is particularly preferred. The content of water in this mixture is preferably 12 to 40 mass%, more preferably 13 to 25 mass%, and even more preferably 15 to 22 mass%, relative to 100 mass% of the mixture. If the content of water is equal to or higher than the lower limit, the recovery rate of the complex catalyst increases due to the solubility of the complex. If the content of water is equal to or lower than the upper limit, the reaction solution is likely to become a homogeneous phase, and the recovery rate of the complex catalyst can be maintained at a good level.

[0165] The mixing ratio (mass ratio) of the poor solvent to the reaction solution varies depending on the type of poor solvent and the composition of the reaction solution, but poor solvent: reaction solution is preferably 5:1 to 15:1, more preferably 6:1 to 10:1, and even more preferably 7:1 to 9:1. If the ratio of the poor solvent is below the upper limit, the amount of the complex catalyst dissolved in the poor solvent decreases, the catalyst recovery rate increases, and the aggregate recovery device can be made smaller. If the ratio of the poor solvent is above the lower limit, the reaction solution is likely to become a homogeneous phase, and the complex catalyst recovery rate can be maintained at a good level.

[0166] The withdrawn reaction liquid may be mixed with a poor solvent as it is, or may be mixed with a poor solvent after at least a part of the reaction medium is removed by distillation or the like.

[0167] The reaction liquid and the poor solvent are preferably mixed under stirring.

[0168] The temperature in the aggregation step is preferably 0 to 70° C., more preferably 0 to 40° C., and further preferably 5 to 20° C. If the temperature during aggregation is equal to or lower than the upper limit, the catalyst recovery rate is excellent. If the temperature during aggregation is equal to or higher than the lower limit, the poor solvent can be kept in a liquid state, and cooling energy can be reduced.

[0169] The aggregation time is not particularly limited, and is usually from 10 minutes to 10 hours, and more preferably from 30 minutes to 5 hours.

[0170] The aggregation step is preferably carried out under an inert gas atmosphere such as nitrogen gas or argon gas in order to prevent the complex catalyst contained in the reaction liquid and the aggregate from being oxidized and deactivated.

[0171] The aggregation step is preferably carried out by stirring the reaction solution and poor solvent under neutral to acidic conditions, since when the liquid containing the aggregates after aggregation is fed to the hydroformylation reaction zone, operations such as washing and neutralization are not required. Usually, the reaction solution extracted from the hydroformylation reaction zone is weakly acidic, and the liquid obtained by mixing this reaction solution with a poor solvent consisting of a mixture of water and alcohol has a pH of about 4 to 7. Therefore, the aggregation operation can be carried out as it is without any particular pH adjustment.

[0172] In this manner, the reaction solution and the poor solvent are stirred in an inert gas atmosphere for a predetermined time at the above-mentioned suitable temperature range, thereby precipitating the aggregate. For this reason, it is preferable to use a sealable glass vessel, a stainless steel vessel, a SUS vessel, or the like equipped with a stirrer as the mixing vessel used in the aggregation step.

[0173] The aggregates precipitated by mixing the poor solvent with the reaction liquid discharged from the hydroformylation reaction zone are sticky under the aggregation conditions. Here, "sticky" means that the precipitated aggregates have an adhesive force sufficient to adhere to the inner surface of the mixing tank in the aggregation step of the present invention. Since the aggregates are sticky in this way, the precipitated aggregates are separated from the liquid in the mixing tank, and due to their adhesiveness, they are attached to the inner surface of the mixing tank, i.e., the bottom surface, inner wall, stirring blades, etc. of the mixing tank.

[0174] That is, in the present invention, the reaction solution containing high-boiling by-products is extracted from the hydroformylation reaction zone and coagulated, so that the coagulate precipitated by coagulation contains the high-boiling by-products as well as the complex catalyst, and the presence of the high-boiling by-products makes the coagulate sticky. In addition, by incorporating the complex catalyst in the sticky coagulate, the complex catalyst can be recovered at a high recovery rate.

[0175] In the production method of the present invention, in order to increase the recovery rate of the complex catalyst by precipitating such a sticky agglomerate, adhering the precipitated agglomerate to the inner surface of the mixing tank, and recovering it, it is preferable to carry out the agglomeration under conditions in which the high-boiling by-products are transferred to the agglomerate at a certain distribution ratio. Specifically, it is preferable to carry out the agglomeration so that, when the total mass of the high-boiling by-products contained in the reaction liquid extracted from the hydroformylation reaction zone is taken as 100 mass%, the lower limit of the distribution ratio of the high-boiling by-products to the agglomerate is preferably 4.0 mass% or more, more preferably 5.0 mass% or more, and even more preferably 6.0 mass% or more. On the other hand, if the distribution ratio of the high-boiling by-products to the agglomerate is excessively high, the yield of the agglomerate decreases, so it is preferable to carry out the agglomeration so that the upper limit of the distribution ratio of the high-boiling by-products to the agglomerate is usually 30 mass% or less, more preferably 20 mass% or less, and even more preferably 10 mass% or less. The upper and lower limits can be combined in any desired manner. That is, the distribution ratio of the high-boiling by-products in the coagulate is preferably 4.0% by mass or more and 30% by mass or less, more preferably 5.0% by mass or more and 20% by mass or less, and even more preferably 6.0% by mass or more and 10% by mass or less, when the total mass of the high-boiling by-products contained in the reaction liquid extracted from the hydroformylation reaction zone is taken as 100% by mass.

[0176] This distribution ratio can be controlled by adjusting the aggregation conditions, such as the composition of the poor solvent, the ratio of the poor solvent to the reaction solution, and the aggregation temperature. The method for measuring the "distribution ratio" will be described in detail later in the Examples section.

[0177] [Recovery process] In the recovery step, the coagulates that have precipitated in the coagulation step and adhere to the inner surface of the mixing vessel are recovered. The recovered coagulates are preferably supplied to the hydroformylation reaction zone.

[0178] Although there is no particular limitation on the method for recovering the aggregates, it is preferable to recover the aggregates by dissolving them in a good solvent for the complex catalyst in the aggregates, since this is an easy operation and can increase the recovery rate of the complex catalyst. Specifically, the liquid in the mixing tank is removed to leave only the aggregates, and a good solvent for the complex catalyst is added to dissolve the aggregates.

[0179] In this case, the good solvent for the complex catalyst is not particularly limited. As the good solvent, those mentioned above as the reaction medium for the hydroformylation reaction or aldehyde, which is the product obtained by the hydroformylation reaction, are preferred because the aggregate solution can be directly supplied to the hydroformylation reaction zone.

[0180] Specifically, when the raw material olefin is propylene, examples of the good solvent include aldehydes such as n-butylaldehyde and i-butylaldehyde, and aromatic hydrocarbons such as benzene, toluene, and xylene.

[0181] The amount of the good solvent used to dissolve the aggregates is not particularly limited, and a smaller amount of the good solvent is preferable from the viewpoint of reducing the volume of the mixing vessel in which the aggregates are dissolved. The amount of the good solvent varies depending on the solubility of the catalyst in the good solvent used and the content of the high boiling point compound in the aggregates, but is usually preferably about 5 to 100 times the mass of the aggregates.

[0182] The temperature condition when dissolving the aggregates in the good solvent is preferably about 5 to 60°C.

[0183] The aggregate dissolved liquid can be supplied as it is to the hydroformylation reaction zone, but if necessary, unnecessary components may be removed by a known separation operation such as distillation, or a solvent or a complex catalyst having high catalytic activity may be added thereto, and then the solution may be supplied to the hydroformylation reaction zone.

[0184] In the present invention, the reaction liquid containing the complex catalyst and the high boiling by-products is extracted from the hydroformylation reaction zone, and a poor solvent is added and mixed in a mixing tank to precipitate a sticky aggregate containing the complex catalyst and the high boiling by-products, and the precipitated aggregate is attached to the inner surface of the mixing tank and recovered. By using such a method, the production method of the present invention can eliminate the loss of the complex catalyst due to the filtration operation of the slurry, and can recover and reuse the complex catalyst at a high recovery rate, compared to the conventional crystallization method in which the complex catalyst is precipitated as non-sticky crystals while removing the high boiling by-products as much as possible, and a slurry in which the crystallized product is uniformly dispersed in the mother liquor is obtained. Therefore, the production method of the present invention can improve productivity without wasting expensive Group 8 to 10 metals such as rhodium in the complex catalyst.

[0185] 2. How Alcohol is Produced The method for producing an alcohol of the present invention uses an aldehyde produced by the method for producing an aldehyde of the present invention. Alcohols can be produced by reacting aldehydes with hydrogen as they are, that is, by subjecting them to a hydrogenation reaction, or by subjecting them to a hydrogenation reaction after dimerization. For the hydrogenation reaction, a known solid catalyst in which a metal such as nickel, chromium, copper, etc. is supported on a carrier can be used. The reaction conditions are usually a temperature of 60 to 200° C. and a hydrogen pressure of about 0.1 to 20 MPaG.

[0186] 3. Catalyst composition The catalyst composition of the present invention is a catalyst composition comprising a catalyst and high-boiling by-products, wherein the catalyst is a long-form Group 8 to 10 metal-organophosphorus complex catalyst of the periodic table, and the content of the high-boiling by-products is 30 mass% or more relative to 100% of the total mass of the catalyst composition.

[0187] The catalyst composition of the present invention, which satisfies the above-mentioned constitution, becomes sticky, and by adhering the catalyst composition to the inner surface of a reaction apparatus such as a mixing tank and recovering the catalyst, the recovery rate of the catalyst can be improved.

[0188] The method for obtaining the catalyst composition of the present invention is not particularly limited, and examples thereof include a method for obtaining the catalyst composition as an aggregate in any one of the first, second, and third embodiments of the aldehyde production method of the present invention described above.

[0189] In the catalyst composition of the present invention, the catalyst may be the same as the catalyst used in the first, second and third embodiments of the above-mentioned process for producing an aldehyde of the present invention. In the catalyst composition of the present invention, the high-boiling by-products may be the same as the high-boiling by-products mentioned in the first, second and third embodiments of the above-mentioned aldehyde production process of the present invention.

[0190] In the catalyst composition of the present invention, the long-form Group 8 to 10 metal-organophosphorus complex catalyst of the periodic table can be the same as the long-form Group 8 to 10 metal-organophosphorus complex catalysts of the periodic table exemplified in the first, second and third embodiments of the above-mentioned method for producing an aldehyde of the present invention.

[0191] In the catalyst composition of the present invention, the lower limit of the content of the high boiling by-product is 30% by mass or more, preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, and particularly preferably 70% by mass or more, based on 100% of the total mass of the catalyst composition, from the viewpoint that the catalyst composition becomes sticky and can be recovered by adhering the catalyst composition to the inner surface of a reaction apparatus such as a mixing tank, thereby increasing the recovery rate of the catalyst such as the complex catalyst. On the other hand, the upper limit of the content of the high boiling by-product is not particularly limited, and from the viewpoint that the catalyst composition is easily precipitated as an aggregate, it can be preferably 97% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less, based on 100% of the total mass of the catalyst composition.

[0192] In the catalyst composition of the present invention, the lower limit of the catalyst content is not particularly limited, and from the viewpoint that the catalyst composition is easily precipitated as an aggregate, it can be preferably 3% by mass or more, more preferably 10% by mass or more, and even more preferably 20% by mass or more, based on the total mass 100% of the catalyst composition. On the other hand, the upper limit of the catalyst content is preferably 70% by mass or less, more preferably 60% by mass or less, more preferably 50% by mass or less, even more preferably 40% by mass or less, and particularly preferably 30% by mass or less, based on the total mass 100% of the catalyst composition, from the viewpoint that the catalyst composition becomes sticky and the catalyst composition can be attached to the inner surface of a reaction device such as a mixing tank and recovered to increase the recovery rate of the catalyst such as the complex catalyst.

[0193] The catalyst composition of the present invention may contain, other than the above-mentioned high-boiling by-products and catalyst, other components such as a reaction solvent and an aldehyde which is the target product of the hydroformylation reaction, in an amount of 10 mass % or less, preferably 5 mass % or less, relative to 100% of the total mass of the catalyst composition.

[0194] 4. Method for producing aldehydes The method for producing an aldehyde of the present invention includes dissolving the above-mentioned catalyst composition of the present invention in a good solvent for the catalyst to obtain a catalyst solution, and subjecting an olefin to a hydroformylation reaction in the presence of the catalyst solution to obtain an aldehyde corresponding to the olefin.

[0195] The method for dissolving the catalyst composition of the present invention in a good solvent for the catalyst to obtain a catalyst solution is not particularly limited, and for example, the same method and conditions as those for obtaining an aggregate solution using the catalyst composition of the present invention instead of an aggregate in the recovery step in any of the first, second and third embodiments of the aldehyde production method of the present invention described above can be adopted.

[0196] In addition, the method for hydroformylating an olefin in the presence of the catalyst solution to obtain an aldehyde corresponding to the olefin is not particularly limited, and for example, the same conditions as those exemplified in the hydroformylation reaction step in any one of the first, second and third embodiments of the above-mentioned aldehyde production method of the present invention can be adopted. EXAMPLES

[0197] The present invention will be described in more detail below with reference to examples. The present invention is not limited to the following examples as long as it does not depart from the gist of the present invention.

[0198] The compounds used in the examples and comparative examples are as follows. Rhodium acetate aqueous solution (rhodium acetate concentration 28% by mass) (product name: Rhodium Acetate L, manufactured by N.E. Chemcat Corporation) n-Butyl aldehyde (purity 99% or more, manufactured by Mitsubishi Chemical Corporation) Methanol (product name: Reagent grade methanol, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Desalted water (Mitsubishi Chemical Corporation)

[0199] Phosphite ligand A (bisphosphite ligand compound shown below, synthesized by the method described in WO 2019 / 039565) [ka]

[0200] (1,5-Cyclooctadiene)acetate rhodium dimer (product name: Rh2(cod)2(OAc)2, manufactured by N.E. Chemcat Corporation)

[0201] [Example 1] A hydroformylation reaction of propylene was carried out using rhodium acetate as the long-form periodic table Group 8 to 10 metal compound and phosphite ligand A as the organophosphorus ligand. Next, the reaction liquid was extracted from the hydroformylation reaction zone, and low-boiling components were distilled off using a distillation method. The composition of the reaction liquid after distillation and before being subjected to a coagulation treatment was as follows. The amount of rhodium atoms in the complex catalyst in the reaction solution was determined by fluorescent X-ray analysis. The amount of n-butylaldehyde was determined by gas chromatography-internal standard method. The amount of phosphite ligand A was determined by high performance liquid chromatography-external standard method.

[0202] (Composition of reaction solution before flocculation treatment) Rhodium atoms in the complex catalyst: 373 ppm by mass Phosphite Ligand A 12006 ppm by mass n-Butyl aldehyde 10.6% by mass Other components (various complexes, high boiling point by-products, etc.) 88.2% by mass

[0203] A 0.5 L glass vessel equipped with an electromagnetic induction stirrer was used as the mixing vessel. The reaction solution thus extracted and a mixed solvent of methanol and water (methanol:water=80:20 (mass ratio)) as a poor solvent were charged into the mixing tank in an inert gas (nitrogen gas) atmosphere at a mass ratio of poor solvent / reaction solution of 9.00. After sealing the mixing tank, the mixture was stirred at 500 rpm and held at a temperature of 10° C. for 2 hours to carry out an aggregation treatment, thereby precipitating a rhodium complex together with high-boiling by-products.

[0204] (Mold of flocculation treatment liquid and properties of flocculants) When the flocculation treatment liquid was visually observed, it was found that the precipitated flocculants adhered to the inner wall of the mixing tank, the stirring blades, etc., and the flocculants and the mother liquor were separated into a solid-liquid state. Moreover, the adhered flocculants had the properties of a sticky substance.

[0205] (Distribution ratio of high boiling by-products in condensate) Thereafter, the mother liquor was removed from the mixing tank, and 400 mL of n-butylaldehyde was added to the mixing tank to dissolve the aggregates adhering to the inside of the mixing tank at room temperature, and the aggregate-dissolved liquid was collected. The content M1 (unit: mg) of high boiling by-products contained in the aggregate solution and the content M2 (unit: mg) of high boiling by-products contained in the mother liquor extracted from the mixing tank were measured by gas chromatography-internal standard method, and the distribution ratio of high boiling by-products in the aggregate was calculated using the following formula. As a result, the distribution ratio was 9.2 mass%. Distribution ratio of high boiling point by-products (mass%) = M1 / (M1+M2) x 100

[0206] (Rhodium recovery rate) As the recovery rate of the complex catalyst, the recovery rate of rhodium was measured according to the following procedure. The amount R1 (in terms of rhodium atoms, units: mg) of the rhodium complex catalyst contained in the aggregate solution and the amount R2 (in terms of rhodium atoms, units: mg) of the rhodium complex catalyst contained in the mother liquor extracted from the mixing tank were measured by fluorescent X-ray analysis, and the rhodium recovery rate (in terms of rhodium atoms, mass%) was calculated using the following formula. As a result, the recovery rate was 96.6 mass%. Rhodium recovery rate (mass%) = R1 / (R1+R2)×100

[0207] (Production of aldehydes) The aggregate solution and toluene as a solvent were mixed, and 54 ml of the resulting mixture was placed in a 0.2 L up-down stirring autoclave in a nitrogen atmosphere, and the autoclave was sealed. The composition of the reaction solution before the hydroformylation reaction was as follows.

[0208] (Composition of reaction solution before hydroformylation reaction) Rhodium atoms in the complex catalyst: 152 ppm by mass Phosphite Ligand A 5929 ppm by mass Toluene 45.0% by mass Other components (various complexes, high boiling point by-products, etc.) 54.4% by mass

[0209] Next, 3.6 g of propylene was fed into the autoclave, and the temperature was raised to 70°C. Then, a mixed gas of hydrogen and carbon monoxide (hydrogen:carbon monoxide = 1:1 (volume ratio)) was injected so that the total pressure in the autoclave was 1.0 MPaA, and the hydroformylation reaction was carried out for 2 hours while maintaining this pressure and temperature. The conversion rate of propylene, the selectivity of propane, the selectivity of aldehyde, the N / I ratio of the target product butyraldehyde (the ratio of n-butyraldehyde to i-butyraldehyde), the half-life of propylene, and the apparent reaction rate (rate constant) of the hydroformylation reaction calculated from the reduction rate of carbon monoxide during the hydroformylation reaction were determined. The evaluation results are shown in Table 2.

[0210] [Reference example 1] In order to compare with the aldehyde production experiment in Example 1, an aldehyde production experiment was carried out using a commercially available rhodium catalyst according to the following procedure. The commercially available rhodium catalyst used was (1,5-cyclooctadiene) acetate rhodium dimer (product name: Rh2(cod)2(OAc)2, manufactured by N.E. Chemcat Corporation). Rh2(cod)2(OAc)2, bisphosphite ligand A, and toluene as a solvent were mixed, and 54 mL of the resulting mixture was placed in a 0.2 L up-down stirring autoclave in a nitrogen atmosphere, and the autoclave was sealed. The composition of the reaction solution before the hydroformylation reaction is shown in Table 2.

[0211] Next, aldehyde was produced under the same conditions as in Example 1, except that the reaction conditions were as shown in Table 2. The evaluation results are shown in Table 2.

[0212] [Examples 2 to 10] The aggregation treatment was carried out under the same conditions as in Example 1 to obtain an aggregate containing a rhodium complex catalyst, except that the composition of the reaction solution before the aggregation treatment or the composition of the poor solvent (water / methanol) was changed as shown in Table 1. Furthermore, the obtained aggregate was used to produce an aldehyde under the same conditions as in Example 1. The evaluation results are shown in Table 1.

[0213] Fig. 2(a) shows a photograph of the appearance of the mixing tank after the aggregation obtained in Example 2. When observed visually, it was found that the aggregates had adhered to the inside of the mixing tank and the reaction liquid after the reaction had been separated into solid and liquid.

[0214] [Comparative Example 1] Except for changing the composition of the reaction solution before the crystallization treatment and the composition of the poor solvent (water / methanol) as shown in Table 1, the crystallization treatment was carried out under the same conditions as the coagulation treatment in Example 1, and a crystallized product containing a rhodium complex catalyst was obtained.

[0215] (Mold of crystallization solution and properties of crystallized product) Figure 2(b) shows a photograph of the appearance of the mixing tank after the crystallization treatment obtained in Comparative Example 1. Visual observation revealed that the crystallization treatment liquid did not separate into solid and liquid, but formed a uniform slurry. In addition, no adhesion of the crystallized material to the inside of the mixing tank was observed.

[0216] (Distribution ratio of high boiling by-products in crystallized product) The obtained slurry was then subjected to solid-liquid separation using a commercially available polytetrafluoroethylene membrane filter with a pore size of 0.5 μm. As in Example 1, the amount R1 (in terms of rhodium atoms, units: mg) of the rhodium complex catalyst contained in the solution of the crystallized product and the amount R2 (in terms of rhodium atoms, units: mg) of the rhodium complex catalyst in the recovered crystallized product were measured by fluorescent X-ray analysis, and the rhodium recovery rate was calculated using the following formula, which was 9.3 mass%. Rhodium recovery rate (mass%) = R1 / (R1+R2)×100

[0217] The relationship between the distribution ratio of high-boiling by-products and the rhodium recovery rate for the coagulates of Examples 1 to 10 and the crystallized product of Comparative Example 1 is shown in FIG.

[0218] [Table 1]

[0219] [Table 2]

[0220] The above results reveal the following: In Examples 1 to 10, the distribution ratio of high-boiling by-products in the aggregate was significantly increased, and the aggregation conditions were controlled so that sticky aggregates were precipitated, so that solid-liquid separation proceeded after the aggregation treatment, and the precipitated aggregates were almost entirely attached to the inside of the mixing tank, specifically, to the stirring blades and introduction tube in the glass container. Furthermore, the rhodium complex catalyst could be recovered in high yield by dissolving and recovering the adhesions from the mixing tank. The results shown in Table 2 show that the rhodium complex catalyst recovered in Example 1 had catalytic performance in the production of aldehyde equivalent to that of a commercially available complex catalyst using a rhodium-based catalyst.

[0221] On the other hand, in Comparative Example 1, the distribution ratio of high boiling point by-products in the crystallized product was low, so the obtained crystallized product was crystallized as non-sticky crystals. The crystallization liquid was in the form of a uniform slurry. When the crystallized product was recovered by filtration, the recovery rate of the rhodium complex catalyst was low.

[0222] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention. This application is based on Japanese patent application No. 2021-202681 filed on December 14, 2021, the entirety of which is incorporated by reference.

Claims

1. A method for producing an aldehyde, comprising hydroformylating an olefin with a gas containing hydrogen and carbon monoxide in the presence of a catalyst, mixing a poor solvent for the catalyst in a mixing tank with a part or all of the reaction liquid discharged from the reaction zone to precipitate a sticky aggregate containing the catalyst; Allowing the precipitated aggregate to adhere to an inner surface of the mixing tank or allowing the aggregate to precipitate in the mixing tank in an aggregated state; the precipitated aggregate in the mixing tank is dissolved in a good solvent for the catalyst, and the resulting solution is supplied to a hydroformylation reaction zone; a distribution ratio of high boiling point by-products contained in the coagulate is 4.0 mass% or more when the total mass of high boiling point by-products contained in the reaction liquid is 100 mass%.

2. The method for producing an aldehyde according to claim 1, wherein the precipitation is carried out under neutral to acidic conditions.

3. The method for producing an aldehyde according to claim 1, wherein the catalyst is a long-form Group 8 to 10 metal-organophosphorus complex catalyst.

4. The method for producing an aldehyde according to claim 3, wherein the catalyst is a long-form Group 8 to 10 metal-phosphite complex catalyst.

5. The method for producing an aldehyde according to claim 3, wherein the long form metal of Groups 8 to 10 of the periodic table is rhodium.

6. The method for producing an aldehyde according to claim 1 , wherein the poor solvent comprises water and an alcohol.

7. The method for producing an aldehyde according to claim 6, wherein the poor solvent is a mixture of water and an alcohol, and the content of the water is 12 to 40 mass% with respect to 100 mass% of the total mass of the mixture.

8. The method for producing an aldehyde according to claim 1 , wherein the aggregate is precipitated under a temperature condition of 0° C. or higher and 70° C. or lower.

9. A method for producing alcohol, comprising producing an aldehyde by the method described in claim 1 and producing an alcohol from the aldehyde.

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