JP2000034252A - Production of aldehyde - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a safe and efficient method for producing an aldehyde by hydroformylation of corresponding olefin, wherein, a rhodium-containing solution is separated from the reaction liquor and is used in a circulatory way as a catalyst. SOLUTION: This method comprises oxidizing a rhodium-containing solution separated from a hydroformylation reaction liquor in the presence of an accelerator, recovering the rhodium and reusing it in a circulatory way as a catalyst, wherein, a means of removing low-boiling point components from the rhodim- containing solution to be supplied to an oxidation treatment process and a means of controlling the supply of the rhodium-containing solution by detecting the low-boiling point components in the above rhodium-containing solution are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a process for producing an aldehyde by hydroformylation of an olefin in the presence of a rhodium-based catalyst. More specifically, the present invention relates to a method for producing an aldehyde which involves a step of separating and recovering rhodium from a rhodium-containing waste catalyst liquid separated from a hydroformylation reaction liquid and reusing the same.

[0002]

2. Description of the Related Art Hydroformylation reaction in which hydrogen and carbon monoxide are added to an olefinic double bond (oxo reaction)
Is well known as a method for producing aldehydes or alcohols. As the catalyst for the hydroformylation reaction, a rhodium-containing catalyst is often used in spite of its high cost because of its excellent activity and selectivity. Therefore, it is indispensable to recycle an expensive rhodium catalyst for industrial use. However, while the catalyst is being recycled in the system, the catalyst gradually deactivates due to the effects of poisonous substances mixed in trace amounts from the raw material olefin, water gas, etc.
It is necessary to continuously or intermittently extract the catalyst from the reaction system and replenish the new catalyst. Various methods have already been proposed for recovering and reusing expensive rhodium from such spent catalysts or deactivated catalysts after the reaction.

For example, a method for recovering rhodium from a distillation residue of a hydroformylation reaction using a triaryl phosphite as a ligand disclosed in Japanese Patent Application Laid-Open No. 54-26218 is disclosed.
Although this method recovers zero-valent rhodium as a precipitate by oxidation using oxygen gas, complicated chemical treatment is required to regenerate the recovered metal into an active catalyst. JP-A-57-72995 discloses a method in which an organic solution containing a Group VIII noble metal is air-oxidized in the presence of a polar organic solvent, water and alkali to crystallize and recover a metal complex. The method of recovering by crystallization or precipitation requires filtration equipment and is not industrially advantageous. JP-A-2-
No. 145439 discloses an organic solution of a complex of rhodium and a non-polar phosphorus ligand such as triphenylphosphine, which is contacted with an aqueous solution of a polar phosphorus ligand such as triphenylphosphine trisulfonic acid (TPPTS). The complex is extracted into an aqueous solution, treated with a conditioning agent capable of reducing the coordination force of these polar phosphorus ligands to the complex, and then re-exposed with an organic solvent containing a non-polar phosphorus ligand. A method for extracting is disclosed. However, this method uses T
Requires polar ligands such as PPTS. Further, in this method, since both the organic phase and the aqueous phase contain a ligand that forms a complex with rhodium, equilibrium occurs and the recovery is low.

JP-A-3-146423 discloses a method of recovering rhodium by treating a distillation residue from a hydroformylation reaction with oxygen gas in the presence of a carboxylic acid and an alkali metal carboxylate, and extracting the resultant with water. However, when the industrially recovered catalyst metal is recycled, it is necessary to pay attention to components mixed in the reaction system. For example,
It is known that in the hydroformylation reaction, the incorporation of an alkali metal salt promotes the formation of high-boiling substances. Therefore, when recycling the recovered catalyst metal,
Almost complete dealkalization metal must be performed in the preceding stage, but it is not easy to remove the alkali metal completely or substantially without affecting the reaction system. US Patent No. 4390
No. 473 discloses that a solution containing rhodium and cobalt used as a catalyst in a low-pressure hydroformylation method is brought into contact with an aqueous solution of formic acid, a gas containing oxygen is passed through, the phases are separated, and rhodium and cobalt are recovered in an aqueous phase. In this method, rhodium is partially separated in a metallic form because formic acid acts in a reductive manner in practice. This metallic form of rhodium is substantially lossy.

Japanese Patent Application Laid-Open No. 2-48419 discloses that after a distillation residue of a hydroformylation reaction is reacted with an oxidizing agent, a rhodium complex is added to the aqueous solution using an aqueous solution containing a water-soluble phosphine or the like in the presence of a water gas. A method for extracting is disclosed. However, these methods are all methods for preparing a rhodium complex in an aqueous solution. In the hydroformylation reaction and the like, the raw material is often insoluble in water, and the reaction is often performed in a non-aqueous organic solution. Therefore, a water-soluble catalyst has problems such as low reactivity due to low solubility of the raw material in an aqueous solution, and these methods are unsuitable as a method for preparing a catalyst for a reaction in an organic solution. JP-A-2-145440 discloses that an aqueous solution containing rhodium and optionally a ligand is treated with an oxidizing agent in the presence of an excess of a water-soluble salt of a carboxylic acid having 7 to 22 carbon atoms to form a water-insoluble compound. A method is disclosed in which rhodium is separated and extracted and recovered with a water-insoluble organic solvent. However, this method requires an operation such as filtration in order to recover rhodium in the organic solvent, which is not desirable.

Japanese Patent Publication No. Hei 8-505137 discloses a method of extracting cobalt from a hydroformylation reaction solution using a cobalt catalyst into an aqueous phase using a water-soluble phosphorus ligand aqueous solution and treating the aqueous solution with a water gas. Discloses a method of extracting cobalt into an organic solvent. However, there is no mention of rhodium. It is known that stable dicobalt octacarbonyl is relatively easily formed by treating cobalt with a gas containing carbon monoxide, but it is difficult to form rhodium carbonyl with respect to rhodium in terms of stability. is there. European Patent (EP)
No. 695734 discloses that rhodium is similarly extracted from a hydroformylation reaction solution using rhodium into an aqueous phase using an aqueous solution of a water-soluble phosphorus ligand, and the aqueous solution is treated with a water gas to convert rhodium into an organic solvent. A method for extracting is disclosed. However, when an organic phosphorus compound that easily forms a complex with rhodium exists in both the aqueous solution and the water-insoluble organic solvent liquid, there are problems such as a low recovery rate of rhodium in the water-insoluble organic solvent liquid. is there.

As described above, many proposals have been made on a method of recovering rhodium from a hydroformylation reaction solution and reusing it as a catalyst. In most cases, oxidation of a rhodium-containing solution separated from the hydroformylation reaction solution is performed. It involves processing. However, all of these methods have problems in industrial implementation and are not always satisfactory. Thus, the present inventors have previously avoided the drawbacks of the prior art, and as a method of efficiently recovering and reusing rhodium from a rhodium-containing hydroformylation reaction liquid, a rhodium-containing liquid separated from the hydroformylation reaction step was used. Is oxidized in the presence of an aqueous medium containing a promoter to extract rhodium into an aqueous phase, and the aqueous phase is treated with a water-insoluble tertiary organic phosphorus compound in a gas atmosphere containing carbon monoxide. A method for producing an aldehyde which is brought into contact with an organic solvent solution to extract rhodium as a tertiary organophosphorus compound complex into an organic solvent and circulated to a hydroformylation step was proposed (EP829).
300).

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing an aldehyde which recovers rhodium by oxidizing a rhodium-containing liquid separated from a hydroformylation reaction liquid and reuses it as a catalyst, as described above. It is an object of the present invention to provide a method which is industrially advantageous, particularly a method which is more secure.

[0009]

Means for Solving the Problems The present inventors have conducted various studies in order to achieve the above-mentioned object, and have found that when a low-boiling component such as a hydroformylation reaction solvent is present in a rhodium-containing solution to be subjected to an oxidation treatment, a small amount of the solvent is present. However, it has been found that depending on the oxidation conditions, there is a risk that low-boiling components may form explosive air. In particular, when incorporating a process of catalyst recovery and reuse in a continuous aldehyde production process, the amount of low-boiling components contained in the rhodium-containing liquid introduced into the oxidation treatment step significantly increases due to erroneous operations in the previous step. In some cases, it was found that it was necessary to provide a mechanism for controlling this amount, and the present invention was reached.

That is, the gist of the present invention is that a) a hydroformylation reaction step of reacting a compound having an olefinically unsaturated bond with carbon monoxide and hydrogen in the presence of a rhodium complex; Separating the liquid and supplying it to a rhodium recovery step; c) recovering the rhodium in the rhodium-containing liquid supplied from the step b through a process of oxidizing in the presence of an accelerator;
A process for recycling the aldehyde to a hydroformylation reaction step as a catalyst, wherein b)
The step comprises means for removing low-boiling components from the rhodium-containing liquid separated from the hydroformylation reaction step and means for controlling the supply of the rhodium-containing liquid by detecting the concentration of the low-boiling components in the rhodium-containing liquid supplied to the step c. And a method for producing an aldehyde. The method of the present invention is widely applicable to a method for producing an aldehyde including the above steps a, b, and c. The steps from recovery of rhodium from the oxidized solution to reuse as a catalyst are not particularly limited. It is preferable to use in combination with the method described in EP829300.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The method of the present invention is applied to a method for producing an aldehyde by hydroformylating a compound having an olefinically unsaturated bond with carbon monoxide and hydrogen in a water-insoluble medium in the presence of a rhodium complex. The compound having an olefinically unsaturated bond as a raw material is not particularly limited, and for example, ethylene, propylene, 1-butene, 2-
Butene, isobutene, butene mixture, butene dimer,
Examples thereof include olefinic hydrocarbons having 2 to 20 carbon atoms, such as hexene, octene, nonene, and propylene trimer, and mixtures thereof, and olefinic compounds having a functional group such as allyl alcohol, vinyl acetate, and vinyl chloride. Preferably, it is an olefinic hydrocarbon.

As the catalyst, rhodium is used alone or in combination with a complex salt forming ligand. As the complex salt-forming ligand, an organic phosphorus compound, specifically, a tertiary alkyl or aryl phosphine or a tertiary alkyl or aryl phosphite is used. Specifically, for example, trialkyl phosphines such as trimethyl phosphine, triethyl phosphine, tripropyl phosphine, tributyl phosphine, trioctyl phosphine, triaryl phosphines such as triphenyl phosphine, tritolyl phosphine, trixyl phosphine, and diphenyl propyl Tertiary alkylarylphosphines such as phosphine and phenyldipropylphosphine are exemplified. Examples of the phosphite include phosphites having low hydrolyzability due to steric hindrance such as triethyl phosphite, triphenyl phosphite, and tris (o-tert-butylphenyl) phosphite. Further, it may be a mixture of phosphine and phosphite. Preferably triarylphosphine,
Particularly preferred is triphenylphosphine.

As the reaction solvent, the olefin itself may be used as the solvent, or an aldehyde formed or a high-boiling product produced as a by-product may be used. In addition, aliphatic hydrocarbons such as hexane and octane, aromatic hydrocarbons such as toluene and xylene, alcohols such as ethanol, isopropanol, butanol, 2-ethylhexanol, ethylene glycol and propylene glycol, ethers such as triglyme, and dioctyl Various solvents that dissolve the catalyst and do not adversely affect the reaction, such as esters such as phthalate, can be used. After the hydroformylation reaction, the crude product is separated by means such as stripping with unreacted gas or distillation, and the catalyst is used in the reaction while remaining in the reaction zone or once taken out and then recycled to the reaction zone. . In any method, in order to avoid accumulation of by-products such as deactivated catalyst metals or high-boiling substances, the spent catalyst liquid containing the catalyst is intermittently or continuously extracted from the reaction zone. The present invention applies to such rhodium-containing liquids separated from the hydroformylation reaction step.

In the rhodium-containing liquid separated from the hydroformylation step, rhodium is dissolved in a solution composed of arbitrary ratios of raw materials, reaction products and by-products, a reaction solvent and the like. Although the method of the present invention can be applied to a reaction solution containing the produced aldehyde, preferably, the catalyst solution after substantially all of the aldehyde has been distilled off by stripping or distillation, and furthermore, a reaction solvent or a high boiling by-product. Is applied to a concentrated catalyst solution, a residual metal-containing solution after removing a part of a ligand or a metal complex from these catalyst solutions, and the like.
More preferably, it is a solution from which the formed aldehyde and the ligand are removed. The concentration of rhodium is not particularly limited, but is preferably from 10 to 10,000 ppm, and more preferably from 50 to 1,000 ppm. Normal,
A catalyst solution from which substantially all of the aldehyde has been removed by stripping or distillation, or a catalyst solution from which the reaction solvent or high-boiling by-products have been removed, or a ligand or metal complex from these catalyst solutions. The residual metal-containing liquid after the partial removal (hereinafter referred to as “extraction catalyst liquid”) contains a small amount of a low boiling component such as a reaction solvent for hydroformylation. When the extracted catalyst liquid containing a small amount of such a low-boiling component is supplied to the catalyst recovery step and is oxidized, the low-boiling component forms a detonation depending on the oxidation treatment conditions. In particular, when the concentration of low-boiling components increases due to equipment failure or erroneous operation in the preceding process, there is a great risk of causing detonation during the oxidation treatment.

The conditions under which low-boiling components form detonation vary depending on the temperature and pressure of the oxidation treatment and the type of oxidizing agent.
It is determined by the relationship between the gas phase concentration of the low-boiling component under the conditions and the explosion limit of the low-boiling component. Therefore, it is essential to reduce the content of low-boiling components in the rhodium-containing liquid (extracted catalyst liquid) to be supplied to the next step as much as possible. The allowable concentration of the low-boiling component in the extracted catalyst liquid is specific to each low-boiling component. Distillation or simple distillation is employed as a method for reducing low boiling components. That is, a low-boiling-point component distillation column is provided immediately before the extracted catalyst liquid is supplied to the oxidation treatment step, and the low-boiling-point component is distilled off from the top of the tower, and the bottom liquid is supplied to the oxidation treatment step. At this time, the concentration of the low boiling point component in the bottom liquid is detected, and the rhodium-containing liquid supplied to the oxidation treatment step contains an amount of the low boiling point component capable of forming a detonation during the oxidation treatment. In this case, it is necessary to take measures to stop the supply. Means for monitoring the concentration of low boiling components in the bottom liquid may be either direct or indirect means for detecting the concentration, but a thermometer with low response time delay and high reliability is used as an indirect concentration detector. Preferably, it is used. Specifically, the relationship between the residual low-boiling-point component concentration in the bottom liquid and the temperature in the column was measured in advance, and at the lower limit of the temperature in the column, a shut-off valve installed in the supply system to the next oxidation treatment step was set. There is a method of providing a control circuit.

The rhodium-containing liquid (bottom liquid) separated from the hydroformylation step is supplied to the next step and is oxidized in the presence of an aqueous medium containing a promoter. Here, the accelerator is a water-soluble substance that promotes a reaction of oxidizing rhodium and extracting it into an aqueous phase, and is a carboxylic acid, an amine or an amine salt, an ammonia or ammonium salt, an inorganic acid or an inorganic acid salt. Etc. are used. Specifically, examples of the carboxylic acid include mono- or dicarboxylic acids such as acetic acid, propionic acid, butyric acid, oxalic acid, malonic acid, malic acid, glycolic acid, lactic acid, and hydroxybutyric acid, and mixtures thereof. The concentration of the carboxylic acid in the aqueous medium is 5 to 50% by weight,
Preferably it is 20 to 40% by weight.

The amines used as accelerators include:
Aliphatic amines, aromatic amines and heterocyclic amines that are soluble in aqueous media are used. Among these amines, an amine which is preferably distributed to an aqueous solution when brought into contact with a rhodium-containing liquid, and which has a polar functional group such as a hydroxy group, an amino group, and a cyano group as a substituent on nitrogen, preferable. Particularly preferred are alkanolamines and diamines. Specific examples of alkanolamines include, for example, methanolamine, ethanolamine, propanolamine, butanolamine, dimethanolamine,
Diethanolamine, dipropanolamine, trimethanolamine, triethanolamine, tripropanolamine and the like. Specific examples of the diamines include, for example, ethylenediamine, tetramethylethylenediamine, and the like. Examples of amines that can be used in the present invention in addition to the above aliphatic amines include aromatic amines such as aniline, and heterocyclic amines such as pyridine, pyrrole, imidazole, and oxazole.

The amine salt can be selected from the above-mentioned organic acid salts and inorganic acid salts of amines. The organic acid salt is a salt of an aliphatic mono- or dicarboxylic acid or a salt of an aromatic carboxylic acid. The carboxylic acids that can be used are mono- or dicarboxylic acids having 2 to 8 carbon atoms such as acetic acid, propionic acid, butyric acid, valeric acid, octylic acid, oxalic acid, malonic acid, malic acid, glycolic acid, lactic acid, and hydroxybutyric acid. Inorganic acid salts include salts such as sulfuric acid and nitric acid.
Further, the amine salt can be generated in the system.
For example, the above-mentioned acid and amine can be separately added to prepare in the system, or when an organic acid or inorganic acid is already present in the hydroformylation reaction solution, the amine can be added to form a salt. The concentration of the amine or amine salt in the aqueous medium is 0.01 to 10 mol / L, preferably 0.1 to 5 mol / L.
1 / L.

The ammonium salt used as an accelerator can be selected from organic acid salts and inorganic acid salts which are soluble in an aqueous medium. Examples of the organic acid salts include the same organic acid salts as in the case of the above-mentioned amine salts. Examples of inorganic acid salts include salts of sulfuric acid, nitric acid, hydrochloric acid, carbonic acid, boric acid, and phosphoric acid. The concentration of ammonia or ammonium salt in the aqueous medium is 0.01 to 10 mol / L, preferably 0.1 to 5 mol / L. Ammonia may be fed in the form of aqueous ammonia or gas, and may be used in combination. Further, the ammonium salt may be formed in the system from an acid and ammonia.

As the inorganic acid or inorganic acid salt, sulfuric acid, nitric acid,
Hydrochloric acid, carbonic acid, boric acid or phosphoric acid and alkali metal salts thereof. Preferred are sulfates and carbonates. The concentration of the inorganic acid salt in the aqueous medium is 0.01 to 10 mol.
/ L, preferably 0.1 to 5 mol / L. Thus, the promoter usually remains in the aqueous phase in which rhodium has been extracted by oxidation treatment in the presence of these promoters. Then, depending on the type of the accelerator, the water-insoluble third
When rhodium is extracted from an aqueous phase into an organic solvent phase using an organic solvent solution of a low-grade organic phosphorus compound, attention must be paid to the remaining amount because the recovery rate of the rhodium complex is reduced. By adding a carboxylic acid to such a system, the recovery rate when rhodium is extracted from the aqueous phase into the organic solvent phase can be improved. Among the above-mentioned accelerators, preferred accelerators are carboxylic acids, especially carboxylic acids having 2 to 4 carbon atoms. Specifically, acetic acid, propionic acid, butyric acid, and oxalic acid are preferable,
Particularly preferred is acetic acid. The amount of the aqueous solution containing the accelerator used is 0.1% based on the rhodium-containing solution to be treated.
It is 10 to 10 times by volume, preferably 0.5 to 4 times by volume.

The oxidation treatment is carried out by contacting with an oxidizing agent. The oxidizing agent is selected from inorganic peroxides such as hydrogen peroxide, organic peroxides such as t-butyl peroxide and octene peroxide, or oxygen or an oxygen-containing gas. Preferably, it is hydrogen peroxide or oxygen or an oxygen-containing gas, particularly preferably an oxygen-containing gas. The oxygen concentration of the oxygen-containing gas can be arbitrarily selected, and a gas obtained by diluting oxygen with an inert gas can be used. Industrially, air is used. The form of feeding the oxygen-containing gas is not particularly limited, and may be either a batch system or a continuous system. The required amount of oxygen is determined by the amount of oxidized substances such as rhodium, ligands, organic substances, etc. in the rhodium-containing liquid. However, a pressurized system is preferable because the recovery depends not only on the total amount of oxygen but also on the partial pressure. The pressure varies depending on conditions such as the oxygen concentration in the gas. For example, when the pressure is air, the pressure is 1 to 150 kg / cm ² G, preferably 10 to 1 kg / cm ² G.
00 kg / cm ² G.

In the oxidizing agent treatment, the rhodium-containing liquid and the accelerator-containing aqueous medium are mixed with sufficient stirring at 60 to 160 ° C., preferably 80 to 150 ° C., more preferably 100 to 140 ° C.
It is carried out by contacting at 0 ° C. The reaction system is not particularly limited, and may be a batch system or a continuous system. Further, once the rhodium is extracted into the aqueous phase, the organic phase after the phase separation is again brought into contact with the aqueous medium containing the accelerator, and it is possible to repeatedly perform the oxidation treatment, in order to improve the recovery rate of rhodium. It is effective for

The details of the mechanism of rhodium recovery in the oxidizing agent treatment are not clear, but are considered as follows. That is, the above-mentioned ligand is eliminated from the rhodium species bonded to the complex-forming ligand present in the solution by the oxidation treatment, and the solubility of the rhodium in the aqueous phase is improved by increasing the oxidation state of the rhodium. Let it. During this oxidation treatment, the oxidized rhodium species migrate to the aqueous phase due to the simultaneous presence of the aqueous medium in the system as compared with the case where the organic phase is present alone, so that the oxidation reaction is more efficient. Is thought to progress.

After the oxidation treatment, the water-soluble rhodium compound obtained by separating the aqueous phase containing rhodium is circulated to the hydroformylation step as a catalyst directly or after being appropriately activated. Preferably, the aqueous phase containing rhodium is fed to the next complex preparation step and brought into contact with an organic solvent containing a water-insoluble tertiary organic phosphorus compound in a gas atmosphere containing carbon monoxide. The water-insoluble tertiary organic phosphorus compound may be any compound having low solubility in the aqueous solution used and high solubility in the organic solvent. These tertiary organic phosphorus compounds include phosphine and phosphite.
Preferred phosphine compounds include triaryl phosphines such as triphenyl phosphine, tritolyl phosphine, and trixylyl phosphine; or alkylaryl phosphines such as propyl diphenyl phosphine and dipropyl phenyl phosphine; and tributyl phosphine, trioctyl phosphine, and tribenzyl phosphine. Is an alkyl phosphine. Preferred phosphite compounds include phosphites that are not hydrolyzable due to steric hindrance, such as triaryl phosphites such as triphenyl phosphite, and tris (o-tert-butylphenyl) phosphite. A mixture of these phosphines and phosphite compounds may be used. Further, when a water-insoluble tertiary organic phosphorus compound is used in the reaction using the rhodium complex solution as a catalyst, it is preferable to use the same organic phosphorus compound. The concentration of the water-insoluble tertiary organic phosphorus compound in the organic solvent is 0.1 to 50% by weight, preferably 0.5 to 30% by weight.
It is.

The organic solvent is not particularly limited as long as it forms two phases with the aqueous phase containing rhodium and can dissolve the tertiary organic phosphorus compound and the resulting complex. Specifically, hexane, heptane and the like can be used. Aliphatic saturated hydrocarbons, benzene, toluene, aromatic hydrocarbons such as xylene, hexene,
Examples include aliphatic unsaturated hydrocarbons such as octene and nonene, esters such as ethyl acetate, ketones such as methyl isobutyl ketone, aldehydes such as butyl aldehyde, valeraldehyde, nonyl aldehyde, and decyl aldehyde, and mixtures thereof. Further, a solvent for the hydroformylation reaction, a reaction mixture, or a concentrate thereof can also be used. Preferably, it is a solvent (reaction liquid) or an aromatic hydrocarbon for the hydroformylation reaction. The contact between the rhodium-containing aqueous phase and the organic phosphorus-containing solution is performed when the volume ratio of aqueous phase / oil phase (organic phase) is 0.1 to 1
It is carried out in the range of 0, preferably 1 to 5.

The contact is carried out under a carbon monoxide atmosphere, preferably under a carbon monoxide and hydrogen gas atmosphere. The volume ratio of hydrogen to carbon monoxide gas is selected from an arbitrary range between 0.1 and 10, and a water gas having a mixing ratio of hydrogen to carbon monoxide of 1: 1 is preferred. The pressure of the water gas is normal pressure to 30
0 kg / cm ² G, preferably 5 to 100 kg / cm ²
G, more preferably 10 to 50 kg / cm ² G.
The effect of carbon monoxide gas in this case is not clear,
It is considered that this promotes the conversion of rhodium in the aqueous phase into a complex that is easily dissolved in an organic solvent. That is, the water-soluble rhodium compound is often a trivalent rhodium compound, but is reduced by carbon monoxide gas to form a monovalent rhodium complex, and forms a carbonyl complex by coordination of carbon monoxide to form an organic solvent. It is thought to promote dissolution in benzene and improve the extraction rate. Further, a complex having good activity can be obtained also as a hydroformylation reaction catalyst by the treatment under a carbon monoxide gas.

The preparation temperature of the carbonyl complex is from room temperature to 20
0 ° C, preferably 80 to 150 ° C, more preferably 1
20-140 ° C. The treatment time is not particularly limited, and is a time during which rhodium is sufficiently extracted into the organic solvent, usually 0.5 to 2 hours. The reaction type may be a batch type, a semi-batch type in which only gas flows, or a continuous type. Further, since this reaction is a three-phase reaction of gas-liquid (water) -liquid (oil), it is necessary to sufficiently contact these three phases. As long as the three-phase contact is sufficiently performed, any reactor such as a stirring tank, a packed type or a column type countercurrent or cocurrent continuous extraction column, or a static mixer may be used. After treatment under carbon monoxide gas,
The organic solvent phase containing the rhodium complex separated from the aqueous phase by phase separation can be circulated as it is to the hydroformylation step as a catalyst, but if the residual amount of the promoter used during the oxidation treatment is large, the catalytic activity will It is preferred to remove the promoter before recirculation to the hydroformylation step, as this reduces the water. As a method for removing the accelerator, extraction using water as a remover (hereinafter referred to as water washing) is preferable,
Either a batch type or a continuous type may be used. If the two phases (oil-water) can be sufficiently contacted, any method such as a stirring tank, a filling type mixer, a countercurrent tower or a static mixer may be used. The water-oil ratio at the time of the water washing treatment is usually selected between 0.5 and 10. From the viewpoint of removing the accelerator, it is preferable that the water-oil ratio is large, but it is preferably in the range of 0.5 to 1 in consideration of the reduction of the wastewater containing the water-soluble accelerator. On the other hand, the aqueous phase after the separation of the organic solvent phase contains an accelerator and can be recycled and reused in the oxidation treatment step. At this time, the whole amount may be reused, but one part may be continuously or intermittently purged in order to prevent accumulation of undesired components, and the accelerator is replenished in order to keep the concentration of the accelerator constant. May be.

[0028]

EXAMPLES The present invention will be described below in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. Example 1 The following process simulation was performed. The organic liquid corresponding to the extracted catalyst liquid separated from the hydroformylation reaction step was distilled using the apparatus shown in FIG. In FIG.
A liquid having the following composition was introduced into the distillation column (3) from the pipe (1) at a rate of 20 kg / h.

[0029]

Table 1 Component Composition (% by weight) Hydroformylation reaction high-boiling by-product 21.5 Hydroformylation reaction heavy-boiling by-product 22.5 Triphenylphosphine 5 Toluene 50 Water 1

The distillation column (3) has three theoretical stages, the top pressure is 100 mmHg vacuum distillation, and the reflux ratio is 1. Toluene distilling from the tower top is condensed (4)
After being condensed, the mixture is led to a reflux tank (5), one part is returned to the distillation column (3) as reflux, and the remaining part is distilled off from the pipe (2) to the outside of the system. The bottom liquid is supplied to the oxidation step via line (6). Here, the relationship between the concentration of toluene (TL) remaining in the bottom liquid and the bottom temperature was as follows.

[0031]

Table 2 Residual TL concentration (% by weight) Column bottom temperature (° C) 3 130 5 112 7 107 9 105

On the other hand, when the next oxidation extraction step was performed under the following conditions,

[0033]

[Table 3] Oxidation extraction pressure 20Kg / cm ² G Oxidation extraction temperature 120 ° C Water-oil ratio 1 Accelerator 20% by weight acetic acid aqueous solution

The relationship between the lower explosive limit combustible substance concentration of the mixture and the combustible substance concentration in the gas phase derived by LeChatelier's law is as follows.

[0035]

[Table 4] TL concentration in the extracted catalyst liquid Lower explosive limit of the mixture Combustible substance concentration in the gas phase (% by weight) Combustible substance concentration (% by volume) (% by volume) 3 1.74 0.71 5 1.560 .96 7 1.47 1.21 9 1.41 1.45

As described above, when the concentration of toluene in the extracted catalyst solution is 9
When the amount of the flammable substance is reached by weight, the combustible substance concentration in the gas phase in the oxidation extraction step exceeds the lower explosive limit combustible substance concentration. In this case, a raw material shutoff circuit (8) in which the lower limit of the tower bottom temperature of the temperature switch (7) installed at the bottom of the tower is set to 120 ° C. is provided. Shut off the feed to the extraction process. This shutoff circuit limits the amount of toluene supplied to the oxidative extraction circuit and will always be below the lower explosive limit of flammable material in the mixture.

Example 2 An organic liquid containing isopropanol was used in place of toluene in Example 1, and the distillation liquid was distilled under the same conditions as in Example 1 except that the distillation pressure was set to normal pressure. The relationship between the residual isopropanol (IP) concentration and the bottom temperature was as follows.

[0038]

Table 5 Residual IP concentration (% by weight) Column bottom temperature (° C) 5 136 7 124 9 118 11 113

Under the same conditions for the oxidation extraction step as in Example 1, Le
The relationship between the lower explosive limit of flammable substances and the concentration of flammable substances in the gas phase of a mixture derived by Chatelier's law is as follows.

[0040]

[Table 6] IP concentration in the extracted catalyst liquid Lower explosive limit of the mixture Combustible substance concentration in gas phase (% by weight) Combustible substance concentration (% by volume) (% by volume) 5 2.3 1.3 7 2.2 1 .6 9 2.2 1.9 11 2.1 2.2

When the isopropanol concentration in the extracted catalyst solution becomes 11% by weight, the concentration of combustibles in the gas phase in the oxidation extraction step exceeds the lower explosive limit combustibles concentration. In this case, the lower limit of the bottom temperature of the temperature switch (7) installed at the bottom is set to 1
A raw material shutoff circuit (8) set at 20 ° C. is provided, and the shutoff circuit is operated to close the shutoff valve (9), thereby shutting off the supply to the oxidation extraction step.

[0042]

According to the present invention, in a method for producing an aldehyde by a rhodium-catalyzed hydroformylation reaction, rhodium is safely and efficiently recovered from a spent catalyst separated from a hydroformylation reaction solution. Then, it can be reused as a catalyst.

[Brief description of the drawings]

FIG. 1 shows a distillation column for removing low-boiling components from a rhodium-containing solution separated from a hydroformylation reaction solution used in an embodiment of the present invention, and a low-boiling component concentration in the bottom liquid of the distillation column is detected to proceed to an oxidative extraction step. Diagram showing a circuit that controls the supply of

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rhodium containing liquid supply pipe 2 Low boiling point component discharge pipe 3 Distillation tower 4 Condenser 7 Temperature switch 8 Shutoff circuit 9 Shutoff valve

Continued on the front page (72) Inventor Kazuyuki Yokoyama 3-10 Utsudori, Kurashiki-shi, Okayama Prefecture Mitsubishi Chemical Mizushima Works Co., Ltd. Mizushima Plant Co., Ltd. F-term (reference) 4G069 AA02 AA10 BA26A BA27B BC71A BC71B BE26A BE27B BE42A CB52 GA10 GA14 4H006 AA02 AC45 AD11 AD16 AD30 BA24 BA83 BA84 BD36 BD52 BE20 BE30 BE40 4H039 CA62 CF10 CL50

Claims (9)

[Claims] 1. a) a hydroformylation reaction step of reacting a compound having an olefinically unsaturated bond with carbon monoxide and hydrogen in the presence of a rhodium complex; b) separating a rhodium-containing liquid from the hydroformylation reaction step; C) recovering the rhodium in the rhodium-containing liquid supplied from the step b through a process of oxidizing in the presence of a promoter,
In the method for producing an aldehyde, the method comprises the step of recycling as a catalyst to the hydroformylation reaction step, wherein the step b supplies to the means for removing low-boiling components from the rhodium-containing liquid separated from the hydroformylation reaction step and to the step c. A method for producing an aldehyde, comprising: means for detecting the concentration of a low-boiling component in a rhodium-containing liquid to control supply of the rhodium-containing liquid. 2. The method for producing an aldehyde according to claim 1, wherein the step c comprises the following steps c-1, c-2 and c-3. c-1) The rhodium-containing liquid supplied from step b is oxidized in the presence of an accelerator-containing aqueous medium to extract rhodium into the aqueous phase, and then separate the aqueous phase from the organic phase. Extraction step, c-2) contacting the aqueous phase containing the water-soluble rhodium compound separated in step c-1 with an organic solvent solution of a water-insoluble tertiary organic phosphorus compound in a carbon monoxide-containing gas atmosphere; And extracting the rhodium in the aqueous phase as a tertiary organophosphorus compound complex into the organic solvent and then separating the organic phase and the aqueous phase. C-3) Rhodium separated in step c-2 Circulating the organic phase containing the tertiary organophosphorus compound complex to the hydroformylation step, 3. Rhodium-third separated in step c-2.
3. The process for producing an aldehyde according to claim 2, wherein the accelerator is removed from the organic phase containing the lower-order organophosphorus compound complex and then recycled to the hydroformylation step. 4. The process for producing an aldehyde according to claim 2, wherein the aqueous phase containing the promoter separated in the step c-2 is circulated to the step c-1. 5. The step b) wherein the rhodium-containing liquid separated from the hydroformylation reaction step is distilled in a distillation column to remove low-boiling components and the temperature of the bottom liquid of the rhodium-containing distillation column is detected. The method for producing an aldehyde according to any one of claims 1 to 4, wherein a bottom liquid supplied to the aldehyde is controlled. 6. The method for producing an aldehyde according to claim 1, wherein the accelerator is a carboxylic acid having 2 to 4 carbon atoms. 7. The method for producing an aldehyde according to claim 1, wherein the promoter is ammonia or an ammonium salt. 8. The method for producing an aldehyde according to claim 1, wherein the accelerator is an amine or an amine salt. 9. The method for producing an aldehyde according to claim 1, wherein oxygen or an oxygen-containing gas is used for the oxidation treatment.