PROCESS FOR RECOVERING CATALYST FOR USE IN PREPARING 1-(4-ISOBUTYLPHENYL) PROPIONIC ACID

Abstract: There is disclosed a process for recovering a catalyst used in the preparation of α-(4-isobutylphenyl)propionic acid, which comprises recovering part of a nickel catalyst component such as nickel carbonyl from a purge gas, and concentrating a reaction product mixture and adding an organic solvent thereto to extract the reaction product, then separating and recovering almost all the part of the catalyst components from the extraction residue. The present invention can provide an efficient process for recovering a catalyst used in the preparation of α-(4-isobutylphenyl)propionic acid.

Description: 1. Field of the Invention This invention relates to a process for recovering effectively catalysts which were used in the industrial preparation of α-(4-isobutylphenyl)propionic acid. α-(4-Isobutylphenyl)propionic acid is a medical raw material for anti-inflammatory, analgesic and antipyretic drugs. 2. Description of the Related Arts The present inventors have already proposed a process for producing α-(4-isobutylphenyl)propionic acid by reacting α-(4-isobutylphenyl)ethyl alcohol with carbon monoxide in the presence of a catalyst comprising a nickel compound, a phosphine compound and an iodine compound, preferably further in the presence of a ketone solvent (EP-A-0 361 021). In order to make the above process more economical, an additional process in which the used catalyst can be recovered and reused effectively is required to be established. In a conventional process for recovering a catalyst used in a homogeneous reaction system, reaction products are distilled out and the catalyst is recovered as a residue. When the above conventional recovering process is applied to the reaction mixture obtained from the said production process for α-(4-isobutylphenyl) propionic acid, the activity of the recovered catalyst was found to be markedly lowered. This is caused by the fact that the activity of the catalyst becomes deteriorated with exposure to high temperatures because of high boiling point of the product. When the distillation is carried out at a relatively low temperature under a reduced pressure, the by-products having high boiling points are found to be accumulated on the catalyst so that the activity of the recovered catalyst is gradually lowered. In GB-A-2 199 030 a process for producing α-phenylpropionic acid derivatives using a rhodium catalyst together with an iodine compound. The catalyst is recovered from the reaction mixture by adding water, and optionally an oxygen-containing organic compound as an extraction solvent. The resulting reaction mixture is thereby separated into two layers, i.e. an organic layer containing the reaction product and a aqueous layer containing the catalyst. This aqueous catalyst can then be repeatedly used. SUMMARY OF THE INVENTION An object of the present invention is to provide a process for recovering a catalyst which has been used in a process for producing α-(4-isobutylphenyl)propionic acid with high efficiency. Another object of the present invention is to provide a process for producing α-(4-isobutylphenyl)propionic acid economically by using the recovered catalyst. The present invention relates to a process for recovering a catalyst comprising a nickel compound, a phosphine compound and an iodine compound used in the preparation of α-(4-isobutylphenyl)propionic acid by reacting α-(4-isobutylphenyl)ethyl alcohol with carbon monoxide, which process comprises recovering a part of the nickel component as nickel carbonyl from a purge gas, adding an organic solvent to a concentrate of the reaction product mixture to extract the reaction products, and separating and recovering the most part of the catalyst components from the extraction residue. DESCRIPTION OF THE PREFERRED EMBODIMENTS A process for producing α-(4-isobutylphenyl)propionic acid is explained. In a preferred example of the process, α-(4-isobutylphenyl)propionic acid is prepared by reacting α-(4-isobutylphenyl)ethyl alcohol with carbon monoxide in the presence of a catalyst comprising a nickel compound as a main component, a phosphine compound as a catalyst coordinate and an iodine compound as a co-catalyst or an auxiliary catalyst. A nickel compound such as nickel iodide, nickel acetate, nickel carbonyl complex and the like can be used as the main catalyst component. The preferred amount of the nickel compound to be used is 10⁻³ to 1 gram nickel atom per mole of α-(4-isobutylphenyl)ethyl alcohol. A phosphine compound such as triphenylphosphine, tributylphosphine and the like can be used as the catalyst coordinate. The preferred amount of the phosphine compound to be used is 1 to 6 in terms of the atomic ratio of phosphine to nickel. As a co-catalyst, an iodine compound such as iodine, methyl iodide and the like can be used. The preferred amount of the iodine compound to be used is 1 to 20 in terms of the atomic ratio of iodine to nickel. It is also appropriate to use a solvent for the above reaction. Preferable solvents include an aromatic ketone such as acetophenone, and an acyclic ketone such as cyclohexanone. The preferred amount of the solvents is 1 to 20 parts by weight based on 1 part by weight of α-(4-isobutylphenyl)ethyl alcohol. The reaction temperature is 50 to 300°C, with the range of 150 to 250°C being preferred for practical use. The reaction pressure is 5 to 500 kg/cm², preferably 10 to 200 kg/cm² as a carbon monoxide partial pressure. When the reaction is carried out under the above conditions, α-(4-isobutylphenyl)propionic acid can be produced with a high yield and a high selectivity. In the following, the process for recovering the catalyst in the present invention is explained in detail. First, in the preparation of the above α-(4-isobutylphenyl)propionic acid, a part of the nickel component in the charged catalyst as a nickel carbonyl accompanies a purge gas or a dissolved gas generated from the product mixture when discharging the mixture out of the reaction system. This nickel component is collected by a cold trap and recovered (hereinafter called as Recovered Catalyst A). In Recovered Catalyst A, 10 to 25% of the nickel component in the charged catalyst can be recovered as nickel carbonyl under the usual conditions. Next, the reaction product mixture drawn out of the reaction system is concentrated, and an organic compound as an extracting solvent is added to the resulting concentrate to extract the reaction product. Then, the most part of the catalyst components can be separated and recovered as precipitate (hereinafter called as Recovered Catalyst B.) Recovered Catalyst B can be obtained by the following procedures. First, the concentration of the reaction product mixture is performed after drawing the mixture out of the reaction system. This concentration can be carried out by evaporation with heating under atmospheric pressure or reduced pressure. It is preferred to reduce the concentration temperature as low as possible in order not to deteriorate the activity of the catalyst recovered. The allowable conditions of the concentration are preferable in the pressure range of atmospheric pressure to 13,3Pa (0.1 mmHg) and a heating temperature range of 50 to 100°C. Concentration ratio of the product mixture is in the range of 0 to 100%, preferably 70 to 90% in terms of a removal ratio of the reaction solvent used. The catalyst recovery process of the present invention can be carried out without the above concentration of the product mixture. But when concentration is effected, the precipitating efficiency of the catalyst components can be enhanced in the subsequent procedures of extracting the reaction product and precipitating the catalyst. Next, the product and the catalyst components are separated from the above concentrate to recover the catalyst components. Preferable examples of the solvents for extracting the product include hydrocarbons such as hexane, heptane, cyclohexane, benzene, and toluene; ethers such as diethyl ether, dioxane, and tetrahydrofuran; and esters such as methyl acetate, and ethyl acetate. Hydrocarbons such as hexane and heptane are particularly preferred. The amount of these extracting solvents is less than 10 parts, preferably 1 to 5 parts based on 1 part of the concentrate. The temperature of the extraction is in the range of 0 to 120°C, preferably 10 to 70°C. When the procedures are carried out under the above conditions, the reaction product is all extracted in the solvent phase, and simultaneously, almost all of the catalyst components are separated and recovered as precipitates (Recovered Catalyst B). In Recovered Catalyst B, 70 to 85% of the nickel component is recovered based on the charged catalyst and nearly 100% of the phosphine component and the iodine component are recovered. When the Recovered Catalyst A and Recovered Catalyst B according to the present invention are mixed up to be used again for the reaction, α-(4-isobutylphenyl)propionic acid can be prepared with sufficient catalytic activity. The process of the present invention can be performed in either the batch system or the continuous system. According to the invention, catalyst components in the production of α-(4-isobutylphenyl)propionic acid, can be recovered and reused in simple operations. Thus, an industrial process of preparing α-(4-isobutylphenyl)propionic acid can be established by the present invention. Accordingly, it has great industrial value. The process of the present invention is explained in more detail by referring to Examples and Comparative examples, but the present invention is not limited by these Examples. Example 1 In an autoclave made of Hastelloy C having an inner volume of 500 ml were charged 80.0g of α-(4-isobutylpheyl) ethyl alcohol, 9.4g of nickel iodide, 11.8g of triphenylphosphine, 6.4g of methyl iodide and 200g of acetophenone as a solvent. Then, carbon monoxide was introduced to the resulting mixture under pressure so that the carbon monoxide partial pressure reached 150 kg/cm², and reacted at 170°C for 2 hours. After completion of the reaction, the autoclave was cooled, the residual gas was purged through a cold trap, and then 317.4g of the reaction product mixture were obtained. In the cold trap, nickel carbonyl was collected in an amount corresponding to 20.5% of the nickel component in the charged catalyst (Recovered Catalyst A). The reaction product mixture was analyzed by gas chromatography. The conversion of α-(4-isobutylphenyl)ethyl alcohol was 99.0% and the selectivity to α-(4-isobutyl-phenyl)propionic acid was 85.9%. About 80% of acetophenone used as a solvent was removed from this reaction product mixture by using an evaporator. Next, 450.0g of n-hexane was added thereto and α-(4-isobutylphenyl)propionic acid and by-products were extracted. Catalyst components precipitated by the above operation were filtered and 24.3g of the catalyst was recovered (Recovered Catalyst B). As the results of analysis of Recovered Catalyst B, it was found that the recovery ratios of nickel, phosphorus and iodine based on the charged catalysts were 72%, 99.9% and 99.9%, respectively. α-(4-Isobutylphenyl)propionic acid was separated and purified by distillation of the hexane extract solution. Nickel in an amount corresponding to 8% of the nickel component in the charged catalysts was contained in the distillation residue. Recovered Catalyst A and Recovered Catalyst B obtained by the above procedures were mixed with the distillation residue, and the resulting mixture was used again as a catalyst for the preparation of α-(4-isobutylphenyl)propionic acid under the same conditions as described above. As a result, the same catalytic activity as the first reaction could be attained, and the conversion of α-(4-isobutylphenyl)ethyl alcohol was 99.2% and selectivity to α-(4-isobutylphenyl)propionic acid was 86.0%. In the above procedure, the distillation residue was added to the recovered catalyst as described above. However, the residue can be disposed to result in no economical problems because of small amount of the residue. In the actual process, the distillation residue can be treated as wastes in order to prevent the accumulation of high boiling point materials, and the reaction can be carried out by supplying a corresponding amount of fresh nickel compound instead of using the residue. Comparative example 1 After preparing α-(4-isobutylphenyl)propionic acid in the same manner as in Example 1, the catalyst components were recovered by direct distillation of the reaction product mixture under reduced pressure. This distillation was carried out under the conditions of a reduced pressure of 0.55 mmHg and a temperature of 130 to 135°C, which is the boiling point of α-(4-isobutylphenyl)propionic acid. Using the distillation residue as a catalyst, α-(4-isobutylphenyl)propionic acid was prepared again in the same conditions as given in Example 1. As a result, the conversion of α-(4-isobutylphenyl)ethyl alcohol was 70.3% and the selectivity to α-(4-isobutylphenyl) propionic acid was 56.6%.

Claims: A process for recovering a catalyst comprising a nickel compound, a phosphine compound and an iodine compound used in the preparation of α-(4-isobutylphenyl)propionic acid by reacting α-(4-isobutylphenyl)ethyl alcohol with carbon monoxide, which process comprises recovering a part of the nickel component as nickel carbonyl from a purge gas, adding an organic solvent to a concentrate of the reaction product mixture to extract the reaction products, and separating and recovering the most part of the catalyst components from the extraction residue. A process for recovering a catalyst according to Claim 1, wherein a part of the nickel catalyst component is collected in a cold trap. A process for recovering a catalyst according to Claim 1, wherein the concentrate of the reaction product mixture is obtained by distillation under atmospheric pressure to 13,3 Pa (0.1 mmHg) at 50°C to 100°C. A process for recovering a catalyst according to Claim 1, wherein the organic solvent is selected from the group consisting of hydrocarbons, ethers and esters. A process for recovering a catalyst according to Claim 4, wherein the organic solvent is selected from the group consisting of hexane, heptane, cyclohexane, benzene, toluene, diethyl ether, dioxane, tetrahydrofuran, methyl acetate and ethyl acetate. A process for recovering a catalyst according to Claim 5, wherein the organic solvent is selected from the group consisting of hexane and heptane. A process for recovering a catalyst according to Claim 1, wherein extraction is carried out at 0 to 120°C. A process for recovering a catalyst according to Claim 7, wherein extraction is carried out at 10 to 70°C.

Inventors: SATO, YOSHIFUMI, SHIMA, YOSHIKAZU, TANAKA, KAZUO, SATO, YOSHIFUMI, C/O MITSUBISHI GAS CHEMICAL INC., SHIMA, YOSHIKAZU, C/O MITSUBISHI GAS CHEMICAL INC., TANAKA, KAZUO, C/O MITSUBISHI GAS CHEMICAL INC.
Applicants: MITSUBISHI GAS CHEMICAL COMPANY, INC.
Application year: 1990
Main classification: C07C57
IPC codes: C07B61, C07C57, C07C51, B01J31