CS254657B1 - A method of preparing ethyl propionate - Google Patents

Abstract

The essence of the method for preparing ethyl propionate, which can be prepared by the action of ethanol on propionic acid under the catalysis of acid catalysts with the addition of substances removing water of reaction, consists in using cyclohexane as a substance removing water of reaction in an amount of 15 to 50% by weight, based on the weight of the reaction mixture. Cyclohexane can be used in the food industry.

Description

The present invention relates to a process for the preparation of ethyl piperione (propionic acid). j »

The preparation of esters of monovalent organic compounds with primary or secondary secondary alcohols is essentially simple. It usually consists of heating the reacting substrates (acids + alcohols) with the addition of an acid catalyst to the reaction mixture. The reaction proceeds according to the general scheme:

R 1 COOH + R 2 OH R 1 COOR 2 + H 2 O where

R 1 is alkyl, cycloalkyl or aryl

R 2 is alkyl, cycloalkyl.

When R 2 is aryl, the reaction proceeds in a low yield and then it is usually necessary to use an acid anhydride or halide.

Since the esterification reaction is an equilibrium reaction, the rate of reaction is stopped if the reaction is carried out in a closed system and an equilibrium concentration, characterized by an equilibrium constant, is reached:

_R = R1COOR2 H2O- ^Kc -R1COOH R2OH

Therefore, under the process conditions, the reaction is carried out in such a way that some of the components from the reaction mixture is continuously removed (usually it is reaction water), thereby achieving complete conversion of the acid, alcohol, or both.

Thus, the greatest problem in esterification is not the preparation of the ester itself, but the removal of some of the reactants and isolation of the desired product, i. j. ester, general separation processes.

This is similar for the preparation of ethyl propionate from propionic acid and ethanol, which can be prepared by the reaction of:

CH3CH2COOH + C2H5OH:

CH3CH2COOCH2CH3 + H2O where the components of the reaction mixture have the following boiling points:

C2H5OH (azeotrope with water) - 78.15 ° C

CH3CH2COOH - 140.96 ° C

CH 3 CH 21 COOCH 2 CH 3 = 99.1 ° C

H10 = 100.0 ° C.

From the above, it can be seen that esterification of 96% ethanol with propionic acid makes it impossible to achieve complete conversion of the reactants, with the desired product having a lower boiling point (and very close to both water and propionic acid).

This problem can be overcome by the process of preparing ethyl propionate by adding ethanol to propionic acid by catalysing acidic catalysts by the addition of a reaction water removal agent according to the invention, wherein the reaction water removal agent is cyclohexane in an amount of 15 to 50% by weight. % by weight of the reaction mixture. Ethanol may be added to the reaction mixture in a single or sequential manner.

The use of cyclohexane yields ethylpropionate useful in the food industry, based on its. relatively low toxicity. Use of other reaction water scavengers, e.g. n-heptane is unsuitable in terms of separation of n-heptane from ethyl propionate since the boiling point of ethyl propionate is 99.1 ° C and n-heptane is 98.4 ° C.

Example 1

A three-necked flask equipped with a rectification column, a thermometer and a distillate overflow (via a siphon) is charged with 111.1 g of propionic acid (1.5 mol), 108.5 g of 95.6% ethanol (2.25 mol), 38 g of cyclohexane (0.45 mol) and 1.5 g of H 2 SO 1 98% catalyst. The reaction is carried out at the boiling point of the reaction mixture. Into the phase separator into which the condensate flows from the deflector of the rectification column, a quantity of cyclohexane is introduced such that only the first portions of the distillate cause the cyclohexane to flow through the siphon cap back into the reaction flask. After separating 45 g of the aqueous phase containing 30 g of reaction water (and water from ethanol), 3 g of ethyl propionate and 12 g of ethanol, cyclohexane, unreacted ethanol is distilled off from the reaction mixture and then the ester formed is distilled off. From the ester may be obtained by about 90 to 95 ° / o, i.e. 135-143 go purity of 99.8% wt., 12 _D ^Z0 - = 1.3850 = 0.889. The residue together with H2SO4 remains as a distillation residue.

Example 2

Under the conditions described in Example 1, 111.1 g of propionic acid (1.5 mol) and 72.3 g (1.5 mol, calculated on 100%), 95.6% ethanol, are metered into the apparatus. . The amount of cyclohexane and H 2 SO 4 is the same as in Example 1. After distilling off the aqueous phase and clarifying the reflex, 18 g of 95.6% ethanol are added to the reaction mixture and the aqueous phase is again distilled off. 18 g of 95.6% ethanol are again added and the aqueous phase is distilled off carefully. Finally, after distillation of cyclohexane and ethanol, from 130 to 140 grams of ethyl propionate having a purity of 99.8% by weight, 12 _d ²⁰ = 1.3850, = 0.889 can be obtained from the reaction mixture. The residue remains in the form of distillation residues containing, in addition to ethyl propionate, sulfuric acid.

Claims (1)

OBJECT OF THE INVENTION A process for the preparation of ethyl propionate by treating ethanol with propionic acid by catalysing acidic catalysts by the addition of reaction water removal agents, characterized in that cyclohexane in an amount of 15-50% by weight, based on the weight of the reaction mixture, is used as the reaction water removal agent.