JPH0566935B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) This invention relates to a method for purifying isophorone. It is known that isophorone can be obtained by alkaline condensation of acetone. However, in this case, secondary products are formed in addition to isophorone, some of which, for example mesityl oxide, can be easily removed by distillation, while others have boiling points that make separation from isophorone difficult. ing. In particular, there is an isophorone isomer, β-isophorone, which is slightly more volatile than isophorone and is a compound that is very difficult to separate by distillation. This compound is colored yellow, making it impossible to obtain colorless isophorone of commercial value. The presence of this substance also promotes a gradual increase in yellow color and an increase in acidity during storage. Therefore, there is a need to develop a method to remove this secondary product and obtain a product isophorone that is clear and colorless and does not lose these properties during storage. The present invention provides a simple and practical method that can fully meet this need. (Prior art) In JP-A-52-51342, in order to neutralize the alkali catalyst present in the isophorone crude liquid obtained from the bottom of the reaction distillation column, an inorganic strong acid is added to adjust the pH from 5 to 9. , preferably within the range of 6.5 to 7.5, thereby suppressing the production of β-isophorone during purification distillation and improving the purity of the final product. However, in this method, pipes become clogged due to precipitation of inorganic salts accompanying neutralization. This drawback can be avoided by removing the salt by washing with water, but this increases the number of processing steps and makes the processing extremely complicated. There is also the problem of equipment corrosion due to the addition of inorganic acids. JP-A No. 54-115350 describes crude isophorone liquid, crude liquid obtained by removing low boiling point components acetone and water from crude isophorone liquid, crude liquid or products obtained by removing alkali substances as catalysts from crude isophorone liquid. Isophorone from 80% using strongly acidic cation exchange resin
It describes a method for producing colorless and stable isophorone by treating it at a temperature of 120°C, neutralizing the waste liquid containing ion exchange resin with an alkaline agent, washing it with water, and then distilling it under reduced pressure. . However, in this method, the discharged treated liquid after being treated with an ion exchange resin is neutralized with an alkaline chemical.
It is necessary to add a buffer to the neutralized mixture and wash it by tilting it with water, which complicates the treatment process and impairs economic efficiency, making it difficult to say that it is practical. (Technical Issue) In view of these problems, the present inventors have conducted extensive experiments and studies, and have determined that the alkaline substances remaining in the crude isophorone solution before distillation are important for the by-product of β-isophorone. We have discovered a fact that has an impact, and have culminated in the present invention. That is, the experimental results are as shown in Table 1.

[Table] Normally, unreacted acetone in the crude isophorone solution synthesized by aldol condensation of acetone with an alkali catalyst is recovered, separated and purified by distillation to obtain isophorone. At this time, the alkaline substance is separated as an aqueous solution, but since the alkali substance remains in the oil layer and enters the distillation column, it is assumed that isophorone isomerizes and becomes β-isophorone during distillation. be done. And here lies the foundation of our technological philosophy. (Means for Solving the Problems) By the way, the method of the present invention is based on the isophorone crude liquid (oil layer) obtained by alkali condensation of acetone.
is brought into contact with a weakly acidic cation exchange resin at room temperature,
The concentration of residual alkaline substances in the treated isophorone
This is a method for purifying isophorone, which is characterized by reducing the temperature to 20 pm or less and then distilling it under reduced pressure. The raw material to be treated in the present invention is an organic layer (oil layer) called crude isophorone liquid, which is obtained by first removing unreacted acetone and then removing most of the reaction water from the reaction mixture flowing out of an aldol condensation reactor using acetone as an alkali catalyst. is the target. The weakly acidic cation exchange resin used in the present invention may be any resin that has excellent solvent resistance to isophorone and adsorbs alkali ions such as sodium in the solution. Here, strongly acidic cation exchange resins are not preferred because they promote decomposition of the target isophorone.
This weakly acidic cation exchange resin (H type) also has the advantage of being easy to regenerate. For example, Mitsubishi Kasei's Diaion WK10, Diamondion WK11, Diamondion WK20, Rohm and Haas' Amberlight IRC-
50, Amberlight IRC-75, Amberlight
IRC-84, Dowex CCR from Dow Chemical Company
Although the present invention can be carried out using a resin commercially available under the trade name 2, it is of course not limited to the resin with this name, and any other resin having similar properties may be used. obtain. The amount of ion exchange resin used is determined by the amount of isophorone crude liquid to be treated per unit time, and usually the residence time of the isophorone crude liquid in the ion exchange resin layer is 0.003 to 0.30 hours, preferably 0.03 hours.
Selected from a range of 0.15 hours. The treatment temperature is usually selected from room temperature (20-50°C). Here, a high temperature of 50° C. or higher is not suitable because there are concerns about the durability of the ion exchange resin used and furthermore the stability of the target isophorone. As for the operation method, either a fixed bed method or a moving bed method can be adopted. Next, the oil layer subjected to the above treatment is subjected to a known vacuum distillation. The operation method can be either batch or continuous high boiling removal followed by low boiling removal. For example, batch distillation requires a reduced pressure of 15 to 30 Torr,
It is appropriate that the column plate size is 20 to 30N and the reflux ratio RR is about 2 to 4. (Effect of the invention) When the isophorone crude liquid (oil layer) is treated according to the present invention and the concentration of alkaline substances in the oil layer is removed to the permissible limit, the formation of β-isophorone is not observed during the subsequent distillation, and it is colorless. And stable product isophorone can be obtained. (Examples) Hereinafter, the method of the present invention will be explained in more detail by giving Examples and Comparative Examples. Example 1 A Ion exchange treatment The raw material to be treated was a crude isophorone liquid (oil layer) obtained from alkali condensation of acetone (composition is the same as that of the charging liquid before distillation). The isophorone crude liquid was poured into an ion exchange resin column filled with Diaion WK11 (trade name of Mitsubishi Kasei Corporation) with a volume of 40 c.c. (10φ x 500H) at a flow rate of 300 at room temperature.
An ion exchange treatment solution was obtained by passing at cc/hr.
(2Hr) By atomic absorption spectrometry, 60ppm of sodium ions were detected in the crude isophorone solution before ion exchange treatment, but this had dropped to 2ppm after treatment. B Vacuum distillation equipment: Older distillation tower 20N (40φ), pressure: 15
The isophorone crude liquid subjected to ion exchange treatment was subjected to batch distillation using ~30 Torr and reflux ratio: RR = 2 to 4. Table 2 shows the results of examining the overall compositional changes before and after distillation. Samples were analyzed using gas chromatography equipped with a flame ionization indicator, and compositions were reported in weight percent.

[Table] Example 2 A Ion exchange treatment The filling volume of ion exchange resin was 2c.c. (10φ×
25H), and the flow rate of isophorone crude liquid was set to 500c.c./
The process was carried out in the same manner as in Example 1 except that Hr was used. 60ppm for isophorone crude solution before ion exchange treatment
of sodium ions were detected, but after treatment,
It had fallen to 20ppm. B. Vacuum distillation The same procedure as in Example 1 was carried out. The results are shown in Table 3.

[Table] Comparative Example B Vacuum distillation Crude isophorone liquid without ion exchange treatment,
It was treated in the same manner as in Example 1 except that it was used directly. The results are shown in Table 4.

【table】

Claims (1)

[Claims] 1. Contact the isophorone crude liquid (oil layer) obtained by alkaline condensation of acetone with a weakly acidic cation exchange resin at room temperature to reduce the concentration of residual alkaline substances in the treated isophorone to 20 ppm or less, and then distill under reduced pressure. A method for purifying isophorone, characterized by: