JPH10291996A - Preparation of rhodium complex solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject solution that is useful as an olefinic hydroformylation catalyst by brining an aqueous solution of a water-soluble Rh compound into contact with a solution of a water-insoluble tertiary organic P compound in an organic solvent, separating the mixture into two phases to recover the organic phase. SOLUTION: A solution containing rhodium recovered from the reaction mixture of olefin hydroformylation is treated with an oxidizing agent in the presence of an accelerator and an aqueous medium. The resultant aqueous rhodium compound solution is brought into contact with a solution of a water- insoluble tertiary organic phosphorus compound (for example, triarylphosphine) in the presence of a carboxylic acid. Then, the reaction mixture is separated into two phases and the organic phase containing rhodium-tertiary organic phosphorus compound complex is recovered whereby the objective rhodium complex solution that is useful as a catalyst for hydroformylation of olefin, hydrogenation, carbonylation and the like is obtained inexpensively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for preparing a rhodium complex solution. More specifically, the present invention relates to a method for preparing a rhodium-tertiary phosphorus compound complex solution used for a catalyst such as an olefin hydroformylation reaction from an aqueous solution of a water-soluble rhodium compound.

[0002]

2. Description of the Related Art Rhodium-containing complexes, for example, rhodium-tertiary organophosphorus compound complexes, are widely used as catalysts for olefin hydroformylation, hydrogenation, carbonylation and the like. Particularly, in the hydroformylation reaction, the catalyst has good catalytic activity and high selectivity to linear aldehydes, and thus is a catalyst widely used industrially.

As a method for preparing a catalyst for these reactions, there are a method in which a complex is prepared in advance and supplied to a reaction system, and a method in which a precursor is directly supplied to the reaction system and converted into a complex in the reaction system. The method of directly supplying the precursor of the catalyst to the reaction system has a problem that the activity of the catalyst is low because the precursor is not sufficiently converted into an effective catalyst.

[0004] As a method for separately synthesizing these complexes, many methods have already been proposed. For example, in a method for preparing a rhodium complex disclosed in JP-A-47-3320, rhodium (II) acetate is reacted with tetrafluoroboric acid and triphenylphosphine, and subsequently treated with an excess of lithium acetate to obtain a target rhodium complex. This is a method for obtaining a triphenylphosphine complex, but requires an auxiliary agent such as tetrafluoroboric acid or lithium acetate, and the operation is complicated.

Japanese Patent Application Laid-Open No. 55-73696 discloses an aqueous solution of rhodium acetate and triphenylphosphine in methanol or N, N
-A method for obtaining a complex which is uniformly dissolved and crystallized in a polar solvent such as dimethylformamide, but which has no polar substituent such as triphenylphosphine;
The low solubility of polar aryl phosphines in polar solvents results in low yields and the loss of rhodium is not large for industrial processes.

A method for synthesizing a rhodium complex from a reaction solution of a catalytic reaction instead of a rhodium salt such as rhodium acetate is disclosed in JP-A-58-116495. Discloses a method for producing a hydride carbonyl tris (triorganophosphorus) rhodium compound by treating a solution diluted with a mixed gas of hydrogen and carbon monoxide in the presence of an organic phosphorus compound. However, in this method, it is necessary to filter the rhodium compound formed, so that the operation is complicated and the yield of the rhodium compound is low.

As described above, the method of separately synthesizing a complex in advance has problems such as complicated operation, low yield, and high cost. Therefore, various studies have been made on a method for obtaining an effective catalyst by a simple operation from an inexpensive rhodium compound or a rhodium-containing solution recovered from a used reaction solution. For example, Japanese Patent Application Laid-Open No. 57-12202
No. 3 discloses a method in which a rhodium salt of a carboxylic acid is complexed in a hydroformylation reaction solvent in the presence of triarylphosphine and water gas. Also, Japanese Patent Application Laid-Open
No. -10624 discloses a method of complexing a water-soluble rhodium compound dissolved in a hydrophilic organic solvent in the presence of a phosphorus compound. In any of these methods, since the rhodium-containing solution is directly introduced into the organic phase by reacting in a homogeneous phase, for example, when an inorganic salt such as sulfate is used as a rhodium source, the inorganic salt is contained in the reaction system. It is undesired because it is mixed and causes a side reaction such as generation of a high boiling point substance.

Japanese Patent Application Laid-Open No. 48-3892 discloses Tris (N.
In recovering rhodium from a catalyst reaction solution using a ligand having a basic nitrogen atom such as (N-diethylaminopropyl) phosphine, the catalyst is extracted into an aqueous phase by treating with an aqueous solution of an acid such as sulfuric acid, A method of extracting and separating the catalyst again by changing the acidity of the aqueous phase is disclosed. However, this method is only applicable to certain organic phosphorus compounds. Further, it is not desirable in that it requires an acid and a base in an amount equal to or more than that of the ligand to be used.

JP-A-59-73052 discloses rhodium and trisulfonated triphenylphosphine (TPPTS).
An acid is added to a catalyst solution containing an alkali metal salt of a water-soluble phosphorus ligand such as, and rhodium is extracted into an organic solution with an organic solvent solution containing an amine, and the organic solution is mixed with an aqueous solution of an inorganic base. A method of recovering a rhodium catalyst in an aqueous solution by contact is disclosed. However, this method is only applicable to catalyst systems containing water-soluble ligands such as TPPTS. Further, it is not preferable in that it requires an acid and a base in an amount equal to or greater than that of the ligand used in the same manner as in the above example.

JP-A-2-145439 discloses an aqueous solution of a polar phosphorus ligand such as TPPTS in an organic solvent solution of a nonpolar complex of rhodium and a nonpolar phosphorus ligand such as triphenylphosphine. Upon contact, the complex is extracted into an aqueous solution. Then, after a treatment with a conditioning agent capable of reducing the coordination force of these polar phosphorus ligands to the complex, a method of extracting again into an organic solvent solution containing a nonpolar phosphorus ligand is disclosed. ing. However, this method uses T
Requires polar ligands such as PPTS. Further, in this method, both the organic phase and the aqueous phase contain a ligand that forms a complex with rhodium, and are equilibrated, resulting in low recovery.

JP-A-2-145440 discloses that an aqueous solution containing rhodium and possibly 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 solution. A method is disclosed in which rhodium is separated as a compound and recovered by extraction 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.

JP-A-2-284651 discloses a method of extracting and recovering rhodium from a reaction solution containing a quaternary organic phosphorus compound obtained by a carbonylation reaction of methanol or the like, acetic acid, or the like with a trialkylphosphine such as tributylphosphine. However, this method does not describe extraction from an aqueous solution containing rhodium. Furthermore, this method is only applicable to liquid phosphine compounds.

JP-A-63-14824 discloses a method in which a monoalkyl phosphoric acid is used as an accelerator when a noble metal is extracted from an aqueous solution containing a noble metal into an organic phase with a phosphorus-based extractant. Trialkylphosphonates, trialkylphosphates and trialkylphosphine oxides are used as extractants. However, since this method uses a pentavalent phosphorus compound, the intended rhodium complex of the water-insoluble tertiary organic phosphorus compound cannot be prepared.

[0014]

As described above, many methods for preparing a rhodium complex used as a catalyst from a rhodium compound have been proposed, but none of them has been satisfactory in industrial practice. . The problem to be solved by the present invention is to avoid such disadvantages of the prior art and efficiently use an inexpensive aqueous solution of a rhodium compound to efficiently form a rhodium-tertiary compound which is effective as a catalyst for hydroformylation, hydrogenation, carbonylation, etc. To provide a method for preparing a high-grade organophosphorus compound complex.

[0015]

According to the present invention, an aqueous solution of a water-soluble rhodium compound is brought into contact with an organic solvent solution of a water-insoluble tertiary organic phosphorus compound, followed by two-phase separation to form a rhodium complex. By extracting to the organic phase to prepare a solution of a rhodium-tertiary organic phosphorus compound in an organic solvent.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The aqueous solution of a water-soluble rhodium compound to which the present invention can be applied is an aqueous solution of an inorganic acid salt of rhodium, an organic acid salt of rhodium, or the like. Examples of the inorganic acid salt of rhodium include rhodium chloride, rhodium bromide, rhodium nitrate, rhodium sulfate, rhodium phosphate, hexachlororhodic acid (H ₃ [RhCl ₆ ]), rhodium ammine complex, for example, chloropentaammine rhodium chloride ( [RhCl
(NH ₃ ) ₅ ] Cl ₂ ) and hexaammine rhodium acid nitrate ([Rh (NH ₃ ) ₆ ] (NO ₃ ) ₃ ). Examples of the organic acid salts of rhodium include carboxylate salts such as rhodium formate, rhodium acetate, rhodium propionate, and rhodium 2-ethylhexanoate. Rhodium sulfate and rhodium acetate are preferred, and rhodium acetate is more preferred. Some of these are usually available as aqueous solutions, and solid rhodium salts may be used by dissolving them in water.

Further, the present invention can be applied to a rhodium-containing aqueous solution recovered from a reaction solution such as a hydroformylation reaction, a hydrogenation reaction, and a carbonylation reaction of an olefin. That is, such a rhodium-containing aqueous solution may be one obtained by directly extracting the reaction solution with an aqueous medium, or one obtained by concentrating the reaction solution and then extracting it with an aqueous medium. Rhodium may be extracted with an aqueous medium after an appropriate treatment such as an oxidation treatment. Preferably, a rhodium-containing aqueous solution recovered from a rhodium-containing liquid used as a catalyst for the hydroformylation reaction is good. Most preferably, the catalyst-containing liquid separated from the reaction solution obtained by performing the hydroformylation reaction in a non-aqueous medium is treated with an oxidizing agent such as oxygen in the presence of an aqueous medium, preferably in the presence of a promoter. This is an aqueous solution obtained by extracting rhodium into water. Here, the promoter is a water-soluble substance that promotes a reaction of oxidizing rhodium in the catalyst solution and extracting it into an aqueous medium, and specifically, acetic acid, propionic acid, butyric acid, oxalic acid and the like. Carboxylic acid, methanolamine, ethanolamine, diethanolamine, trimethanolamine, amines such as ethylenediamine or organic salts of these amines, amine salts such as inorganic acid salts, ammonia or ammonium salts of organic acids or inorganic acids, sulfuric acid, nitric acid, Inorganic acids such as hydrochloric acid, carbonic acid, boric acid and phosphoric acid, and salts of these inorganic acids.

The rhodium concentration in the aqueous solution to which the method of the present invention is applied is not particularly limited as long as the rhodium complex formed is within an amount capable of dissolving in an organic solvent, but is usually from 1 to 10,000 ppm, Preferably 10 to 1000
ppm. The rhodium aqueous solution may be any as long as it can form two phases with the organic solvent solution of the tertiary organic phosphorus compound to be brought into contact, and may be a lower alcohol having 1 to 4 carbon atoms such as methanol, ethanol, propanol, ethylene glycol, ethylene glycol monomethyl. It may contain a polar solvent such as a glycol such as ether or diethylene glycol dimethyl ether or an alkyl ether thereof, or a lower carboxylic acid having 2 to 5 carbon atoms such as acetic acid, propionic acid or butyric acid. The content of these polar solvents in the aqueous solution is not particularly limited as long as two phases can be formed with the organic solution, but is usually selected from the range of 0 to 50%. It is particularly preferable that a carboxylic acid coexist as a polar solvent.

In a preferred embodiment in which a carboxylic acid coexists, a catalyst-containing liquid separated from a hydroformylation reaction solution or the like is treated with a carboxylic acid as a promoter, treated with an oxidizing agent, and then extracted with an aqueous medium using an aqueous rhodium solution. Is preferred. Alternatively, a carboxylic acid may be added to a rhodium compound aqueous solution and used as a raw material of the present invention. On the other hand, when a polar nitrogen-containing compound or a tertiary organic phosphorus compound which easily forms a water-soluble complex with rhodium in the aqueous solution is present, the tertiary organic phosphorus compound in the water-insoluble organic solvent solution to be extracted is used. And coordination equilibrium between these compounds and the coordinating compound in the aqueous solution, which is not preferable. Examples of such nitrogen-containing compounds include amines. Therefore, when an amine is used as the accelerator, it is necessary to minimize the amount of amines remaining in the aqueous rhodium compound solution after extraction. Rhodium and polar tertiary organophosphorus compounds that easily form a complex include trisulfonated triphenylphosphine and its salts, monosulfonated triphenylphosphine and its salts, tricarboxylated triphenylphosphine and its salts, It is a sulfonated or carboxylated phosphine or phosphite compound such as dibisphenylphosphinoethane monosulfonate and a salt thereof.

The water-insoluble tertiary organic phosphorus compound used in the method of the present invention may be any compound having low solubility in the aqueous rhodium compound solution and high solubility in the organic solvent used. These tertiary organic phosphorus compounds include phosphine and phosphite. Preferred phosphine compounds include triphenylphosphine,
Triarylphosphines such as tritolylphosphine and trixylylphosphine; alkylarylphosphines such as propyldiphenylphosphine and dipropylphenylphosphine; and trialkylphosphines and triaralkylphosphines such as tributylphosphine, trioctylphosphine and tribenzylphosphine. . Preferred phosphite compounds include triaryl phosphites such as triphenyl phosphite and phosphites having low hydrolyzability due to steric hindrance such as tris (o-tert-butylphenyl) phosphite. A mixture of these phosphines and phosphite compounds may be used. Preferred tertiary organic phosphorus compounds are triarylphosphines, especially triphenylphosphine. 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 amount of the water-insoluble tertiary organophosphorus compound used is at least an amount that forms a monodentate or bidentate coordination compound with rhodium in the aqueous rhodium solution, and is usually used in a large excess. 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.

The organic solvent used in the method of the present invention may be any solvent which forms two phases with the aqueous solution and can dissolve the tertiary organic phosphorus compound and the complex formed. As specific examples, hexane, aliphatic saturated hydrocarbons such as heptane, benzene, toluene, aromatic hydrocarbons such as xylene, hexene, octene, aliphatic unsaturated hydrocarbons such as nonene, ethyl acetate and the like Examples include esters, ketones such as methyl isobutyl ketone, aldehydes such as butyraldehyde, valeraldehyde, nonylaldehyde, and decylaldehyde, and mixtures thereof. Further, a solvent for the reaction using the rhodium complex catalyst, the reaction mixture itself, or a concentrate thereof may be used. Preferably, it is a reaction solution of a reaction using this catalyst or an aromatic hydrocarbon.

The volume ratio of the aqueous solution to the organic solution to be brought into contact with the organic solution is in the range of 0.1 to 10, preferably 1 to 5, in terms of the volume ratio of the aqueous phase / organic phase (oil phase). The temperature of the contact treatment is selected from room temperature to 200 ° C, preferably from 80 to 150 ° C. Most preferably, it is 120 to 140 ° C. The time of the contact treatment is not particularly limited as long as the rhodium complex is sufficiently extracted into the organic solvent, but is usually about 0.5 to 2 hours.

The reaction system may be either a batch system or a continuous system. In addition, since this reaction is a liquid-liquid two-phase reaction, it is desirable that these two phases be sufficiently contacted. If this two-phase contact can be carried out sufficiently, a stirring tank, a packed type or a column type countercurrent or cocurrent continuous extraction column,
Any reactor such as a static mixer may be used. The contact treatment reaction is performed in an atmosphere of an inert gas such as nitrogen gas, and the pressure is not particularly limited, but is usually selected from a range of normal pressure to 100 kg / cm ² G.

[0024]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the present invention. In the examples,
“%” Means “% by weight” unless otherwise specified.

(Preparation of Water-Soluble Rhodium Compound Aqueous Solution) After removing unreacted raw materials, product aldehyde, reaction solvent, and the like from a propylene hydroformylation reaction solution catalyzed by a rhodium-triphenylphosphine complex, mainly a hydroformylation is carried out. A reaction solution comprising a high-boiling substance and triphenylphosphine was prepared in the presence of a 20% aqueous acetic acid solution.
After oxidation treatment with air, the aqueous phase was separated to obtain an aqueous solution containing a rhodium compound. The following experiment was performed using this rhodium compound aqueous solution.

Example 1 150 mL of an aqueous rhodium compound solution having a Rh concentration of 121.1 mg / L in terms of metal and triphenylphosphine (TP
P) 50 mL of a toluene solution containing 25% (water / oil = 3)
Was charged into a 0.5 L induction rotary stirring type autoclave under a normal pressure under a nitrogen atmosphere, and was subjected to 1,000 rpm at 120 ° C. for 2 hours.
m. Next, the temperature was lowered, and after standing, the organic phase (oil phase) and the aqueous phase were separated. The rhodium concentrations in the aqueous and oil phases were analyzed by Zeeman atomic absorption spectroscopy. From the analytical values, the ratio (recovery) of rhodium in the aqueous solution charged to the oil phase was determined by the following equation. The result was 98.1%.

[0027]

## EQU1 ## Recovery rate (%) = 100−Rh amount of aqueous phase / Rh amount of aqueous solution charged × 100

Examples 2 and 3 A rhodium aqueous solution was treated in the same manner as in Example 1 except that the temperature and pressure were changed. The results are shown in Table 1 below together with the results of Example 1.

[0029]

Table 1 Table 1 Example Pressure Temperature Charged Rh Concentration Rh Recovery No. kg / cm ² G ° C mg / L% 1 normal pressure 120 121.1 98.2 normal pressure 130 97.3 98.9 3 18 120 110.2 99.2

Examples 4 and 5 A rhodium aqueous solution was treated in the same manner as in Example 1 except that the concentration of triphenylphosphine in the organic solvent solution was changed. The results are shown in Table 2 below.

[0031]

Table 2 Table 2 Example TPP concentration Charged Rh concentration Rh recovery rate No. % Mg / L% ─────────────────────────────4 10 82.2 96.0 55 109.5 99.8

Examples 6 and 7 Rhodium aqueous solutions were treated in the same manner as in Example 1 except that the number of revolutions of the stirrer during the reaction was changed. The results are shown in Table 3 below.

[0033]

[Table 3] Table 3 Example Rotation speed Charged Rh concentration Rh recovery rate No. rpm mg / L% ─────────────────────────────6 400 134.1 95.0 7200 110.2 94.9

Example 8 Rhodium compound aqueous solution 15 having a Rh concentration of 82.2 mg / L
0 mL and 50 mL of a toluene solution of 25% triphenylphosphine were charged into a 0.5 L induction-rotation stirring autoclave under a normal pressure under a nitrogen atmosphere, and the mixture was heated at 130 ° C. for 2 hours at 60 ° C.
Stirred at 0 rpm. Next, the same treatment as in Example 1 was performed. The recovery rate of Rh was 96.7%.

[0035]

According to the method of the present invention, a rhodium complex solution that can be directly used as a reaction catalyst can be prepared from an inexpensive aqueous rhodium solution recovered from a hydroformylation reaction solution or the like by simple means. . In addition, rhodium in an aqueous solution can be recovered in an extremely high yield and reused as a complex.

Continued on the front page (72) Inventor Kazuyuki Yokoyama 3-10 Ushidori, Kurashiki-shi, Okayama Pref.

Claims (5)

[Claims] An organic solvent containing a rhodium-tertiary organic phosphorus compound complex after contacting an aqueous solution of a water-soluble rhodium compound and an organic solvent solution of a water-insoluble tertiary organic phosphorus compound, and then separating the two phases. A method for preparing a rhodium complex solution, comprising recovering a phase. 2. The preparation of a rhodium complex solution according to claim 1, wherein the aqueous solution of a water-soluble rhodium compound and an organic solvent solution of a water-insoluble tertiary organic phosphorus compound are brought into contact in the presence of a carboxylic acid. Method. 3. The method for preparing a rhodium complex solution according to claim 1, wherein the aqueous solution of a water-soluble rhodium compound is an aqueous solution containing rhodium recovered from a reaction solution for hydroformylation of an olefin. 4. An aqueous rhodium compound solution obtained by treating a rhodium-containing solution separated from an olefin hydroformylation reaction solution with an oxidizing agent in the presence of an accelerator and an aqueous medium. The method for preparing a rhodium complex solution according to any one of claims 1 to 3, wherein: 5. The method for preparing a rhodium complex solution according to claim 1, wherein the water-insoluble tertiary organic phosphorus compound is a triarylphosphine.