JP2562689B2 - Purification method of dialkyl carbonate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for purifying dialkyl carbonate.

More particularly, it relates to a method for purifying a dialkyl carbonate, which is characterized in that a high quality product having an extremely low content of impurities such as chlorine and aldehyde is obtained.

Dimethyl carbonate, diethyl carbonate, etc.
It is widely used in industry as a raw material for pharmaceuticals and agricultural chemicals, as a raw material for various resins represented by polycarbonate resins and carboneodiol, and as a solvent for various organic syntheses.

PRIOR ART Dialkyl carbonates are generally produced from phosgene and alcohol as shown in formula (1).

The dialkyl carbonate synthesized from phosgene is dehydrochlorinated with an alkaline aqueous solution, an ammonia aqueous solution, an organic amine, etc., and further distilled and refined to become an industrial product.

The by-product of this reaction is an alkyl chloroformate formed from phosgene and alcohol. Formaldehyde (HCHO) produced from phosgene and water,
Formic acid (HCOOH) etc. are considered.

The dialkyl carbonate produced by the reaction as described above cannot completely remove these by-products even if it is purified by ordinary distillation, so that it is unavoidable that a small amount is contained as an impurity.

When a dialkyl carbonate containing these impurities is used as a raw material for pharmaceutical and agricultural chemicals, the yield of the reaction cannot be sufficiently obtained, or the product quality is deteriorated. Further, when used as a resin raw material, the resin is colored, which is not preferable.

Regarding the coloring of this resin, a method of removing an alkyl chloroformate by adding an epoxy compound has been attempted in JP-A-60-181125.

However, this method cannot remove aldehyde components and formic acid components among various impurities.

[Problems to be Solved by the Invention] In view of the situation of the prior art as described above, the present inventors have proposed the removal of impurities such as alkylchloroformate, formaldehyde, and formic acid in dialkyl carbonate to overcome the above-mentioned problems. As a result of intensive studies, they found that aromatic amines, particularly diphenyl and diaminosulfone, were extremely effective for the above purpose, and completed the present invention.

[Configuration of Invention] That is, the present invention is <However, R is a purification method of dialkyl carbonate characterized by adding aromatic amines to a dialkyl carbonate compound represented by CH ₃ —, CH ₂ CH ₃ —> and performing distillation purification.

The present invention is intended to purify a dialkyl carbonate without using a complicated means.

The point of the present invention is that the so-called 99% or higher purity high purity dialkyl carbonate, which has been used as a product in conventional applications as it is, is subjected to a catalytic reaction with amines such as aromatic amines to produce a dialkyl carbonate in the product. The purpose is to remove aldehyde, chlorine and formic acid to obtain higher quality and higher purity alkyl carbonate which is desired in the industry.

Aromatic amines that can be used in the purification method of the present invention include aniline, P-phenylenediamine, phenylhydrazone,
2,4-dinitrophenylhydrazone, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 3,3'-diaminodiphenylmethane, etc. There is.

It may be in the form of powder, tablets, granules, or one dissolved in a solvent, and may be carried on a carrier or coated, and its shape is not particularly limited.

In the present invention, the dialkyl carbonate to be purified is synthesized from phosgene by the reaction shown below.

The produced hydrochloric acid (HCl) is usually neutralized with NaOH, KOH, ammonia, amines, etc., and then removed, and then purified by distillation.

The method of the present invention may be used for further purification of the dialkyl carbonate purified by distillation, or the method of the present invention may be used for ordinary distillation purification.

As a specific treatment method, an additive is added to a dialkyl carbonate to be subjected to a purification treatment, a contact reaction is performed at a constant temperature for a predetermined time, and then, separation purification is performed by distillation.

The amount of the additive such as the aromatic amine used with respect to the amount of the dialkyl carbonate to be treated differs depending on the content of the impurities, and therefore cannot be said to be the case.

Generally, it is recommended to use the following usage amount as a reference.

As an example, when the concentration of aldehyde is, for example, 50 to 500 ppm, it is one standard to use the additive at about 100 to 3000 ppm.

This is because if the amount of the additive used is less than 100 ppm, the removal effect is low, the contact time is long, and conversely 30 ppm or more is wasted.

The aromatic amine used is preferably not sublimable at high temperatures.

This is because simple distillation, which is the most popular distillation method, is possible and it efficiently reacts with aldehydes, chlorine, formic acid, etc.

In the present invention, when 4,4′diphenyldiaminosulfone is used as an additive and when the impurity is an aldehyde, the reaction proceeds according to the following reaction formula.

When impurities are chlorine components with the same additive as above, the reaction proceeds according to the following reaction formula. The acid component such as formic acid forms a salt with an amine.

After adding aromatic amines to dialkyl carbonate,
The conditions for the contact reaction are 80 ° C to 120 ° C and 1
~ 2 hours is sufficient.

After the reaction, the dialkyl carbonate is distilled and purified.
Although a distillation column may be used, a simple distillation without a distillation column is usually sufficient.

Batch distillation using a distillation can may be carried out, or continuous purification may be carried out using a thin film evaporator.

The reaction product of the above-mentioned impurities and the added amines is contained together with the high boiler in the bottom liquid of the bottom after collecting the purified dialkyl carbonate.

The dialkyl carbonate purified by such a method has lower acid content, aldehyde content, and chlorine content than those purified by ordinary distillation, and is useful as a raw material for medicines and agricultural chemicals and a raw material for resin.

For example, when a polycarbonate diol, which is attracting attention as a urethane resin raw material, is synthesized with the alkyl carbonate obtained in the present invention, a very good color is obtained.

[Effects of the Invention] The effects of the method of the present invention will be specifically described below with reference to Examples and Comparative Examples (see Table 1 for reference).

(Example-1) (1) 800 g of commercially available diethyl carbonate synthesized from phosgene and 0.8 g of diphenyldiaminosulfone were added to a 1 round-bottomed flask, heated by a mantle heater and subjected to contact reaction at 100 ° C for 2 hours. I went.

Distillation time is 3.5 hours including contact time and product yield is 95%
Met.

After resinification, a predetermined amount of distilled and purified diethyl carbonate and 1,6-hexanediol (Ube sample product) were charged into the reaction vessel, and a suitable amount of catalyst was charged into the reaction vessel, and the temperature was gradually raised by the esterification reaction. The produced alcohol is continuously taken out of the system, and in order to further increase the molecular weight, the 1,6-hexanediol is reacted under reduced pressure to obtain a polycarbonate diol having an average molecular weight of 2000.

 This distillate was used for resinification.

(Comparative Example-1) (When a precision distillation purification column is used) A diethyl carbonate similar to that used in Example 1 was placed in a 1 round bottom flask equipped with a 10-plate (40φ) plate-type glass distillation column. After 800 g was added, the mixture was heated with a mantle heater and totally refluxed for 1 hour, and then distilled at a reflux ratio of 10. 80 g of the first fraction was obtained.

 Further, it was distilled at a reflux ratio of 1.

 At this time, the temperature at the top of the column was 128 ° C.

The distillation was completed in about 6 HR, and the product yield was 80%. This distillate was used for resinification.

(Comparative example-2) 800 g of the same diethyl carbonate as used in Example-1 and epoxy resin (Epicoat
828, oiled shell epoxy strain) (8 g) was added, and a contact reaction was carried out at 100 ° C. for 2 hours with a mantle heater, and the temperature was further raised to carry out simple distillation. The distillation time was 3.5 hours including the catalytic reaction, and the product yield was 90%.

After resinification, charge a predetermined amount of distilled and purified diethyl carbonate and 1,6-hexanediol (Ube sample) into the reaction vessel. Charge a suitable amount of this catalyst into the reaction vessel and gradually raise the temperature to carry out the esterification reaction. The alcohol produced by the method is continuously taken out of the system, and in order to further increase the molecular weight, the 1,6-hexanediol reaction is performed under reduced pressure to obtain a polycarbonate diol having an average molecular weight of 2000.

 This distillate was used for resinification.

(Comparative example-3) Resination was performed using the commercially available diethyl carbonate synthesize | combined from the same phosgene as used in Example-1.

The results of comparing the impurity content in the diethyl carbonate used for resinification and the hue of the product after resinification are shown in Table 1. The aldehyde content is the hydroxyamine hydrochloride method,
The chlorine content was measured by the combustion method.

It can be seen that the diethyl carbonate of Example-1, which has a much higher distillation yield than when purified by a distillation column, has a small amount of impurities and is excellent in the hue of the product after resinification.

Claims (1)

(57) [Claims] 1. <However, R is CH ₃ —, CH ₂ CH ₃ −> A method for purifying a dialkyl carbonate, which comprises distilling and purifying by adding an aromatic amine to a dialkyl carbonate compound.