JPH0615491B2 - Purification method of acetic anhydride - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for purifying acetic anhydride. Acetic anhydride is widely used as a raw material for acetyl cellulose, medicines, agricultural chemicals, dyes and the like.

(Prior art and problems) As a method for producing acetic anhydride, a method in which vapor such as acetic acid, acetone or methyl acetate, ethyl acetate is thermally decomposed to absorb and react the produced ketene gas with acetic acid, anhydrous aluminum chloride, etc. There is known a method of reacting acetic acid with phosgene by using as a catalyst or a method of heating ethylidene diacetate in the presence of a catalyst such as zinc chloride. As a side reaction, acetic anhydride obtained by these known methods produces diketene by dimerization of ketene itself, and diketene, which is considered to be generated by thermal aging of acetic anhydride itself in a reaction step or the like, in acetic anhydride. And mix these acetic anhydrides with
In the case of purifying by a known method such as distillation, the boiling point difference between acetic anhydride and diketene may be small, and it is necessary to carry out precision distillation with a high reflux ratio and a high number of stages, resulting in a high energy cost. Further, even if the energy cost was ignored, it was impossible to obtain acetic anhydride without diketene detection (5 PPM or less) as in the present invention.

Diketene is very reactive, so
The commercial value of acetic anhydride used as a raw material for facial cleansers and the like significantly depends on the content of diketene as an impurity.

An object of the present invention is to provide a purification method for industrially obtaining high-quality acetic anhydride having a low content of diketene.

(Means for Solving Problems) The present inventors have found that high-quality acetic anhydride can be easily obtained by treating crude acetic anhydride containing diketene with an ion exchange resin. Further, depending on the type of ion exchange resin used and the like, this treatment may cause some coloration, but it was further found that this can be solved by simple distillation such as simple distillation, and the present invention was completed.

That is, the present invention is a method for purifying acetic anhydride, which comprises treating crude acetic anhydride containing diketene with an ion exchange resin and, if necessary, distilling the crude acetic anhydride simultaneously with or after the treatment.

Ion exchange resins are roughly classified into anion exchange resins and cation exchange resins. Although any of these can be used in the present invention, it is preferable to use an anion exchange resin for removing the diketene.

Specifically, as an anion exchange resin, Amberlite IR
A-68, IRA-94, IRA-93 Amberlyst A-21 and the like, and examples of the cation exchange resin include Amberlyst-15 and the like. (Amber Light, Amber List is ROHM
The registered trademark of And Haas Co., Ltd. and the product sold by Organo Co., Ltd.) It When the amount of the ion exchange resin is constant with respect to the raw material crude acetic anhydride to be treated, the effect is greater when the treatment temperature is higher and the treatment time is longer. The temperature does not need to be particularly specified either, and practically, the room temperature is selected from the temperature of about 140 ° C. which is the boiling point of acetic anhydride. In the practice of the present invention, for a predetermined amount of raw material crude acetic anhydride,
Ion-exchange resin is usually added in an amount of 0.1 to 1.0 wt% and stirred at room temperature at 130 ° C for 1 to 3 hours, or the treated solution is subjected to simple distillation under a reduced pressure of about 100 Torr in a batch system. You can In this case, the ion-exchange resin recovered by different treatment liquids or simple distillation can be repeatedly used.

In addition, a predetermined amount of crude acetic anhydride was charged into the evaporator of the simple distillation apparatus, an ion-exchange resin corresponding to about 0.5 to 1 wt% was charged, and continuously charged so that the distillation time was 2 to 8 hours. It can also be treated by a method of distilling it in. Furthermore,
Crude acetic anhydride is circulated in a column packed with an ion exchange resin at room temperature for about 2 to 20 hours, and after the diketene concentration falls below a predetermined amount, this treatment liquid is subjected to simple distillation under a reduced pressure of about 100 Torr. You can also do it.

In this case, the ion exchange resin can be used repeatedly without refilling or re-forming. Even after repeated use 15 times, no particular decrease in effect was observed.

(Effect of the Invention) Diketene in acetic anhydride can be economically removed to 5 PPM or less (not detected) by a simple method. Further, the ion-exchange resin used for the treatment can be easily separated, and the obtained high-quality acetic anhydride can be used as a raw material for fine chemical fields such as medicines and agricultural chemicals without any problem.

Example-1 100 g of raw material crude acetic anhydride was placed in each flask, 1 g of a different kind of ion exchange resin was added to each flask, and the mixture was stirred at room temperature for 1 hour and then analyzed by gas chromatography. did. The results are shown in Table 1. Since the ion exchange resin contains water, this water was used after being sufficiently removed. The ion-exchange resins used in the following experiments were dehydrated by the same pretreatment.

Example-2 100 g of raw material crude acetic anhydride was put in each Erlenmeyer flask, and ion-exchange resin (Amberlyst A-21) was put into this.
3 levels with 0.1g, 0.5g or 1.0g and temperature of 30
℃, 70 ℃ and 130 ℃ 3 levels, processing time 1 hour, 2
After 3 hours of time and 3 hours were taken and the mixture was stirred at a predetermined temperature for a predetermined time, GC analysis was performed. The results are shown in Table-2.
It was the street.

Example-3 and Comparative Example 1 400 g of raw material crude acetic anhydride was placed in a distillation flask, 2 g of an ion exchange resin (Amberlyst A-21) was added, and continuously charged at 50 ml / H under a reduced pressure of 100 Torr and continuously 50 ml. /
Distillation was carried out by distilling with H 2. About 4,000 ml was treated by this method, and the result of GC analysis of this distillate was as shown in Table-3. No diketene was detected at all in the case where about 100 ppm of diketene in acetic anhydride was treated by the same method as above.

Table 3 also shows the results of a comparative experiment in which the same treatment as above was carried out except that no ion exchange resin was added.

Example-4 Put 3000 ml of raw material crude acetic anhydride into a container equipped with a circulation facility,
It was circulated for 150 minutes at room temperature using a pump through a column packed with 30 g of an ion exchange resin (Amberlyst A-21). Table 4 shows the GC analysis results of this treatment solution and that obtained by simple distillation under a reduced pressure of 100 Torr. Note that the quality of the product treated by repeating the same experiment using the same raw material crude acetic anhydride 12 times by the above-mentioned method without changing the ion-exchange resin was the same as shown in Table 4, In particular, no deterioration in the performance of the ion exchange resin was observed.

Claims (1)

[Claims] 1. A method for purifying acetic anhydride, which comprises treating crude acetic anhydride containing diketene with an ion exchange resin and, if necessary, distilling the crude acetic anhydride simultaneously with or after the treatment.