SU1505925A1 - Method of producing esters - Google Patents

Abstract

The invention relates to carboxylic esters, in particular, to the preparation of esters of primary alcohols, which are used in the food and perfume industry. The goal is to intensify and simplify the process. Obtaining the target products are the interaction of primary alcohols with acids on a stationary layer of cation exchanger with azeotropic distillation of water and simultaneously with the recycling of the reaction mass. The boiling point of the azeotropheater should not exceed the boiling point of the starting components and reaction products. The speed of the process increases 4.5 times, the catalyst is not destroyed and works without a decrease in activity of more than 120 hours. 1 Il.

Description

The invention relates to organic chemistry, in particular, to the synthesis of esters of primary alcohols boiling above 140 ° C under atmospheric pressure and obtained by the esterification reaction of primary alcohols with carboxylic acids, which are used in the food industry as flavoring agents, in perfumery - “schlennost as fragrant substances, in the cosmetic industry as preservatives, and also as solvents.

The aim of the invention is to intensify the process and simplify the technology of producing esters

The drawing shows a schematic diagram of the reactor in which the reaction is carried out.

A distillation column 5, designed for better separation of vapors from the distilled azeotrope containing the genus from the volatile components of the reaction mixture, water separator 6 and cooler 7, is attached to the top of the tank 1. There is a fine-grained layer on the glass wool filter layer placed on the perforated bottom. cation exchanger 3. A circulating device 2 is attached to the tank 1, which is an evaporator, into which a mixture from the bottom enters from below

31505

tanks 1. The outlet from the evaporator is attached to the top of the tank 1 above the cation exchanger layer. The evaporator 2 is heated by a coolant (steam). Before starting work, the initial mixture is poured into the tank 1 and the heat carrier is fed into the evaporator jacket 2. The mixture in the evaporator boils and the resulting vapors eject the liquid components of the mixture into container 1, into the space above the cation exchanger 3 layer. In this case, the evaporator 2 acts as a gas lift a pump in which the working pairs are formed pairs. The vapors pass through the column 5, are condensed in the refrigerator 7, and the condensate is collected in the water separator 6, where it is returned to the tank 1 after filling it through the column 5. The liquid components of the mixture pass through the layer of cationite 3 and re-enter the evaporator 2 from below, as a result, there is an intensive circulation of the mixture through the layer of cation exchanger 3. When the mixture is heated to boiling, water begins to be distilled from it along with the azeotropifying agent. Water is collected in the water separator 6 and continuously removed from the system, and the azeotropifier flows into tank 1 through column 5. The cation exchanger in the reactor remains stationary. is he

not crushed and can be used

used many times.

In order to combine high speed of the process with high removal of the product per unit volume of the reactor, it is advisable to carry out the process

continuously, In this case, the reaction is carried out in a cascade of several (usually a couple of reactors) connected in series. In each of the reactors, the mixture enters through the plug 9 and exits through the overflow tube 8. The whole system works and is calculated as a cascade of perfect mixers. The duration of the process is determined by the feed rate of the initial mixture and is chosen such that the conversion of spth to ether reaches 96-98%.

Example 1 (comparative). In a flask equipped with a Dina-Stark agitator and an adapter with a fridge, 1 hour was charged, dehydrated sulfonic cation exchanger KU-2-8, 10 h, isoamyl alcohol, 7.5 parts acetic acid 5 0 25 30

five

five

Q

0

five

You (molecular ratio alcohol: acid 1: 1.1) and 6.8 h of azeotrophoreizer - a mixture of ethyl acetate and cyclohexane 1: 1. The mixture is boiled with stirring, collecting the resulting water in the nozzle. The process is carried out for 3 hours before the termination of the water separation. The temperature of the mixture at the same time rises from 92 to 105 ° C. After completion of the reaction, the mixture is filtered from the partially ground cation exchanger and dispersed. Distilled azeotropically and an excess of acetic acid with traces of isoamyl alcohol is used in a subsequent operation. The isoamyl acetate (14.7 parts) left in the cube is washed with a 10% soda solution to remove traces of acetic acid and is distilled. Get 1A hours of marketable isoamyl acetate (yield 95%).

Example 2OB reactor load 1 part of the dehydrated cation exchanger KU-2-8, 10 Cho isoamyl alcohol, 7.5 parts of acetic acid and 6.8 parts of azeotropically. In the shirt of the evaporator serves the heated coolant. After boiling the mixture in the water separator, water containing 2-2.5% acetic acid begins to collect. The process is carried out for 3 hours until the separation of water stops, i.e., until the isoamyl alcohol is almost completely converted. After treatment of the reaction mixture as in Example 1, isoamylacetate is obtained in a yield of 95%. The result obtained indicates that in the reactor used in this example, and in a reactor with a cation-exchange suspended reaction, the reaction rates are the same, that is, the reactor of the proposed design operates as an ideal displacement apparatus.

I

Example ZoV of the conditions of example 2 is carried out by the reaction of 12.3 parts of benzyl alcohol and 5 parts of acetic acid in the presence of 6.8 parts of azeotropifying agent and 1 Cho of cation exchanger KU-2-8s. Reaction time 2.5 hours, conversion alcohol is almost quantitative. After distillation of the reaction product in the presence of 0.5 h, boric acid, which binds the residue of benzyl alcohol, first at atmospheric pressure and then at 30 mm Hg. a perfume fraction of benzyl acetate is obtained, the total yield

which taking into account the re-distillation of non-perfume fractions of 91%.

Example 4. Under the conditions of Example 2, the reaction was carried out with a portion of hexagonal alcohol and 7.5 hours of acetic acid in the presence of 6.8 parts of an azeotropologizing agent and 1 part of a cation exchanger KU-2-8. The reaction time is 3 hours with almost complete conversion of hexyl alcohol. After distillation of the mixture, hexylacetate was recovered with a yield of 93%.

Example 5. Under the conditions of Example 2, 4.8 parts of n-propanol was reacted with 3.3 parts of para-hydroxybenzoic acid (the alcohol: acid ratio was 3.34: 1) in the presence of 1 part of anhydrous cation exchanger KU-2-8 and 1.4 parts of cyclohexane. The distillation of the aqueous azeotrope, boiling at 66.6 ° C and containing 8.5% of water, is led through column 5 with an efficiency of 5 tons to improve its separation from the pair of propanol-cyclohexane azeotrope, boiling at 74.7 ° C. Reaction at a temperature between 100 and 103 ° C for 6 hours until the separation of the aqueous layer, which is 30% aqueous propanol, is stopped. Conversion of parga-ox ibenzoic acid and propyl ester 96%. The reaction mixture is drained from the reactor, cyclohexane is distilled from it with propanol until the temperature of the mixture reaches 115 ° C, and the bottom residue is cooled. The precipitated propyl ether crystals are filtered off (mp. 96-96.5 ° C) . Yield 67.6%.

When re-evaporation of the mother liquor receive an additional amount of ether (so pl. 96-97 C). Yield 19.6%.

Water is added to the remaining secondary mother liquor and aqueous propanol is distilled off. The remainder - slightly yellowish propyl ether crystals have so pl. 95.5-96.3 ° C. The total yield of propyl ether is 92%. I

Example 6. Conducting the esterification reaction in a continuous installation.

The reaction is carried out in a cascade of four reactors (see drawing), which are interconnected by means of overflow tubes. A cation exchanger is loaded into each kada kada reactor in an amount that is 5 times greater than

05925.

cationite in the reactor according to example 2, and the reactor is filled with cation exchanger more than half. Left over

, the space above the cation exchanger serves as a separator for separating vapors from liquid splashes. In total, 20 parts of the dehydrated cation exchanger KU-2-8 are loaded into the cascade of reactors and served every hour 10 but a mixture containing 40 parts of isoamyl alcohol, 30 hours of acetic acid and 27 parts of azeotropifying agent — a mixture of ethyl acetate and cyclohexane (1: 1) . Duration of stay

(5 mixtures in a cascade of reactors for 40 minutes. The temperature from the first reactor to the last is from 90 to. In the resulting mixture, isoamyl alcohol conversion is 98%.

20 The rate of distillation of the azeotropically forming agent in each reactor of the cascade is selected so that all the water that forms is completely removed from the mixture. After processing the mixture in the conditions of example 2, commercial isoamyl acetate is obtained with a yield of 93.1%.

Thus, the proposed method of producing esters due to the continuous circulation of the reaction mixture through a fixed bed of cation exchanger with simultaneous distillation of water allows esterification with high speed and high yield.

jr When testing a method using a continuous scheme on a stand installation using the example of obtaining hexyl acetate, it was found that the process speed increases 4.5 times, the catalyst

40 is not destroyed and works without a decrease in activity of more than 120 hours; there is no need for a special stage of separation of the cation exchanger from the reaction product, which leads to a substantial intensification of the entire esterification process.

In addition, the process technology is greatly simplified: due to the relative increase in the content of cation exchanger in the mixture and, consequently, the acceleration of the process, it becomes possible to create a continuously operating installation, which makes it possible to reduce the total volume of the reactor several times, to facilitate its installation and maintenance. During the reaction the cation exchanger does not lose its activity for a long time and is not ground. With stirring,

grind, it needs to be replaced, since crushed cation exchanger easily clogs the filter. The proposed method makes it possible to eliminate the filter-1F1O and the technological stage of catalyst removal.

Claims (1)

Invention Formula The method of producing esters by the interaction of primary alcohols with acids on cation exchanger at the same time, the boiling point of the azeotropulant should not exceed the boiling point of the initial I components and reaction products, characterized in that, c. the purpose of intensification and simplification of the process, the latter is carried out on a stationary layer of cation exchanger, at that azeotropic distillation of water is carried out simultaneously with the recycling of the reaction mass. ea (shch / omno Water