RU2631425C1 - Method of producing esters of dicarboxylic acids - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: esters of dicarboxylic acids are widely used in paint and cosmetic industry, and as a base (base component) in the production of synthetic lubricating oils for various purposes. The method of producing esters of dicarboxylic acids, characterized in that esterification of dicarboxylic acids selected from terephthalic, sebacic and a mixture of organic acids with monohydric alcohol 2-ethylhexanol (2-EG) is carried out under supercritical conditions, namely, at the phase transition point at a temperature of not less than 340°C and pressure of, at least, 2.76 MPa for 30 minutes.

EFFECT: invention solves technical problem for improving the technology of production and expansion of raw materials for production of esters of dicarboxylic acids.

1 tbl, 3 ex

Description

The invention relates to organic chemistry, specifically to a method for producing esters of dicarboxylic acids, and can be used to obtain esters of dicarboxylic acids from various raw materials.

Dicarboxylic acid esters are widely used in the paint and varnish and cosmetic industries, as well as as a base (base component) in the production of synthetic lubricants for various purposes.

A known method of producing ester of sebacic acid [Patent SU No. 443024. Publ. 07/18/1974]. The esterification of sebacic acid with 2-ethylhexyl alcohol is carried out using C ₁₂ -C ₂₀ synthetic fatty acids, such as tin stearate, at a temperature above 160 ° C and a vacuum above 600 mm Hg as a divalent tin salt. rest to achieve an acid value of 0.1-0.2 mg KOH / g of substance. The method provides a yield of up to 99.2% and an increase in the purity of the target product. The disadvantage of the process is the use of tin compounds (the tin content in the stearate is 17.3%), since the environmental characteristics of the production process are deteriorating. In addition, as a prerequisite for a successful process, the authors note the need for a good tightness of the system, which in reality is difficult. This direction has not received further development.

A known method for producing symmetric esters of dibasic carboxylic acids With ₆ -C ₁₀ and 2-ethylhexanol [Patent RU No. 21114819. Publ. 07/10/1998], used as lubricants for various engines, engine oils, gear oils, hydraulic and brake fluids, and also for plasticizing polymers.

The method includes two stages of the interaction of C ₆ -C ₁₀ acids with 2-ethylhexanol: in the first stage, the esterification is carried out with a gradual increase in temperature to 135-170 ° C at a pressure from atmospheric to residual 400 mm Hg. until the acid number reaches 50-35 mg KOH / g of the substance, then the catalyst is introduced tetra-butoxy titanate or tetraisopropoxy titanate, or a mixture thereof in an amount of 0.01-0.5 wt. % by weight of dibasic acid, and the second stage of esterification is carried out at 180-195 ° C, reducing the pressure to 2-150 mm Hg until the 2-ethylhexanol is distilled off, after which the reaction mass is cooled and treated with water or 1-4% a solution of soda ash in an amount of 1-4 wt. % of the mass of ether - raw. The yield of di- (2-ethylhexyl) adipate is 99.20%.

Closest to the claimed invention is a method for producing esters of dicarboxylic acids With ₄ -C ₆ used to obtain a plasticizer [Patent RU No. 2057115. Publ. 03/27/1996]. Reagent 1: dicarboxylic acid melt is a waste product of adipic acid, consisting of a mixture of 22-24% succinic, 42-46% glutaric, 30-33% adipic acid, 0.5-0.7% nitric acid and 0.5-3 % unidentified impurities. Reagent 2: cyclohexanol. Reaction conditions: the mass ratio of acid: alcohol is 1: 3-3.5, the catalyst is tetrabutoxytitanium, taken in an amount of 0.5-1.5% by weight of dicarboxylic acids, the temperature is 140-180 ° C, and the process is carried out until the cessation of precipitation water, followed by distillation of the excess alcohol by vacuum distillation with selection of a fraction with a boiling point of 160-190 ° C and neutralization.

The product is a plasticizer - a mixture of esters of dicarboxylic acids C4-C6. T. bale. 160-190 ° C, 2-3 mm Hg, flash point 180-182 ° C. The yield of plasticizer is 67%.

The disadvantages of this method include:

- the presence in the process of a titanium-organic catalyst that cannot be regenerated;

- low (up to 87 wt.% for raw materials) yield of the target product;

- the need for the process in several successive stages;

- the need for neutralization of reaction products using alkali;

- high negative impact during the process on the environment.

The present invention solves the technical problem of improving the production technology and expanding raw materials for the production of dicarboxylic acid esters, due to the application of supercritical parameters in the production process and the use of various types of raw materials.

The problem is solved in that the process of esterification of dicarboxylic acids with a monohydric alcohol 2-ethylhexanol (2-EG) is carried out under supercritical conditions, namely at the phase transition point at a temperature of at least 340 ° C, a pressure of at least 2.76 MPa without using a catalyst.

As dicarboxylic acids, terephthalic acid (TFA), sebacic acid (SC) are used, a by-product of the production of terephthalic acid is a mixture of organic acids (COA), which consists of 85% terephthalic acid, 14% p-toluic acid, 1% p-carboxybenzaldehyde .

The specified method is carried out as follows: the process of esterification of pure terephthalic acid (TFA) or a mixture of organic acids (SOA) is a by-product of the production of terephthalic acid or sebacic acid (SC) with ROH monohydroxy alcohol, where R = C ₆ - 2-ethylhexanol (2- EG), without using a catalyst under supercritical conditions, namely, at the phase transition point at a temperature of at least 340 ° C, a pressure of at least 2.76 MPa, for 30 minutes, followed by stepwise separation of the reaction mixture to separate the reaction products .

Example 1. In a metal thick-walled reactor with a volume of 500 ml load 30 g of pure terephthalic acid and 47 g of 2-ethylhexanol in a molar ratio of acid / alcohol = 1/2. The process was 30 minutes, temperature not less than 340 ° С, pressure not less than 2.76 MPa.

Get a mixture of target and by-products. Data on the composition of the reaction products are presented in table 1 (column TFK / 2EG).

Example 2. In a metal thick-walled reactor with a volume of 500 ml load 30 g of a mixture of organic acids (JUIC) - a by-product of the production of terephthalic acid), and 47 g of 2-ethylhexanol in a molar ratio of acid / alcohol = 1/2. The process was 30 minutes, temperature not less than 340 ° С, pressure not less than 2.76 MPa.

Get a mixture of target and by-products. Data on the composition of the reaction products are presented in table 1 (column SOK / 2EG).

Example 3. In a metal thick-walled reactor with a volume of 500 ml, load 30 g of sebacic acid (SC) and 20 g of 2-ethylhexanol in a molar ratio of acid / alcohol = 1/2. The process was 30 minutes, temperature not less than 340 ° С, pressure not less than 2.76 MPa.

Get a mixture of target and by-products. Data on the composition of the reaction products are presented in table 1 (column SK / 2EG).

The resulting products were analyzed on a gas chromatography-mass spectrometer GCMS-QP2010 ULTRA, SHIMADZU.

From the data of table 1 it can be seen that the proposed method for producing esters of dicarboxylic acids, in comparison with the prototype, has the following advantages:

- higher yield of the target product when using various types of raw materials;

- the possibility of carrying out the process in one stage;

- does not require the use of catalysts;

- does not require the use of alkali to neutralize reaction products;

- virtually no negative impact on the environment, i.e. fully consistent with the concept of "green chemistry".

Claims (1)

A method of producing dicarboxylic acid esters, characterized in that the process of esterification of dicarboxylic acids selected from terephthalic, sebacic and a mixture of organic acids is carried out with monohydric alcohol 2-ethylhexanol (2-EG) under supercritical conditions, namely at the phase transition point at a temperature not less than 340 ° C and a pressure of at least 2.76 MPa for 30 minutes.