DE2400007A1 - PROCESS FOR THE PRODUCTION OF ACID CHLORIDES - Google Patents

Description

The invention relates to an improved method of manufacture of acid chlorides.

The generation of acid chlorides by the reaction of a carboxylic acid with carbonyl chloride is already in the US patents 3 184 506, '3 544 626, 3 544 627 ,. 3,547,960 and in the UK Patent 540,096. In these previously known methods long reaction times or high temperatures are necessary.

It has now surprisingly been found that by Reaction of a carboxylic acid with carbonyl chloride in the presence of a tertiary amine catalyst and an acid chloride medium,

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which corresponds to the acid chloride to be formed, the use high temperatures and pressures is avoided and the reaction time is reduced quite considerably.

The tertiary amine catalysts of the present invention are compounds represented by the general formula

^R 2 f
^R 3

are reproduced, in which R., Rp and R, independently of one another are selected from alkyl, aryl, cycloalkyl, alkaryl and aralkyl radicals having 1 to 25 carbon atoms.

Examples of suitable tertiary amines are trimethylamine, triamylamine, Tribenzylamine, t-butyldimethylamine, methylethylbutylamine, Tetradecyldimethylamine, tricyclohexylamine and triphenylamine.

The carboxylic acids which can be used in the present invention are aliphatic and cycloaliphatic mono- and polycarboxylic acids, arylaliphatic acids and aromatic mono- or polycarboxylic acids. Examples of suitable carboxylic acids are isophthalic acid, phthalic acid, terephthalic acid, benzoic acid, toluic acid, trimesic acid, Glutaric acid, adipic acid, sebacic acid, lauric acid, stearic acid, azelaic acid, cyclohexane-l ^ -dicarboxylic acid and cyclopentanedicarboxylic acid.

When carrying out the reaction using low-melting acids, the carbonyl chloride formed in the reaction can serve as the sole reaction solvent when the acid to be converted melts at an inappropriately high temperature, then the preformed acid chloride can be used as the reaction solvent.

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The process according to the invention can be carried out either in batch, semicontinuous or continuous operation will. A suitable method for the preparation of the acid chloride on a continuous basis is to eirue mixture of the acid, the acid chloride and the catalyst to the head of a heated vertical reaction vessel. The mixture then flows continuously through the The reaction vessel descends and meets the phosgene gas continuously flowing up in the reactor in countercurrent. The product stream out Acid chloride and catalyst are then withdrawn from the bottom of the reactor.

In practice, the novel catalyst of the present invention is used in a catalytic amount. The expression "Catalytic amount" refers to the amount of catalyst that the reaction between the carboxylic acid and the carbonyl chloride ■ effectively catalyzed to give the desired acid chloride in high yields. It has been found to be a suitable amount of the tri-substituted tertiary amine catalyst about 0.1 mol # up to about 2.0 mol / s based on the moles of the carboxylic acid and preferably from about 0.5 mol- $ to about 1.0 mol- $.

The pressure is not critical and the reaction can take place at atmospheric pressure be performed. -

The operating temperature for the preparation of the acid chlorides by the process according to the invention depends on the choice of the carboxylic acid used. In general, a preferred temperature range between about 120 ⁰ C and about l60 ° C.

When carrying out the reaction in the manner described above, it was found that the desired acid chloride can be obtained in a convenient manner in yields of 9 to 99 %, based on the total content of the acid, and that undesired by-products either not at all or only in insignificant amounts are formed.

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The reaction times are reduced quite considerably by using the new catalysts and the acid chloride medium according to the present invention compared to the reaction times which are required with other catalysts and solvents. This is particularly the case ₃ when the process is carried out at temperatures above 100.degree.

The acid chlorides formed can by any process, for example by distillation or by recrystallization, getting cleaned.

The amount of the catalyst is preferably from 0.1 mol # to 2.0 mol / 2, based on the moles of the carboxylic acid and especially 0.5 to 1.0 mol / L are preferred. The reaction can be carried out at atmospheric pressure, preferably in the temperature range from 120 to. 160 ° C.

The following examples serve to further explain the principle and the practical implementation of the present invention Invention.

Example I.

70 g of liquefied terephthaloyl chloride, 33.2 g (0.2 mol) of terephthalic acid and 0.30 ml of triethylamine were placed in a 250 ml flask equipped with a thermometer, mechanical stirrer and dry ice condenser. The slurry was stirred, heated to 150 ° C. and kept at that temperature with a thermostat. Phosgene was then bubbled into the reaction mixture at a rate of 0.5 g / min and for about 85 minutes until a sharp drop in the temperature of the reaction mixture was observed and the solid acid completely disappeared. Distillation of the product under vacuum gave 109 g of terephthaloyl chloride (97.5 % based on acid). The boiling point was 1 ^ 7 to 1 ^ 9 ° C at 15 mm; Melting point 8H to 84.5 ° C.

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Example II

Example I was repeated except that isophthaloyl chloride and isophthaloylic acid were used in place of the terephthaloyl chloride and terephthalic acid. The yield of isophthaloyl chloride was -109.5 g (98.2 % based on the acid). The boiling point was 160 to 162 C / 25 mm; the melting point was 43 to 43.5 ⁰ C.

Example III

200 g of liquefied isophthaloyl chloride, 166.2 g of isophthalic acid and 2.5 ml of triethylamine were placed in a 1 liter flask equipped with a thermometer, mechanical stirrer and dry ice condenser. The slurry was stirred, heated to 150 ° C. and kept at that temperature by means of a thermostat. Phoage gas was then introduced at a rate of 2.0 g / min. After about 110 minutes, a sudden drop in the reaction temperature was observed, which was associated with a simultaneous disappearance of the last traces of the solid acid. The phosgenation was stopped and an additional 332.4 g of isophthalic acid was added to the reaction vessel. No further catalyst was added. Phosgenation was continued at a rate of about 4 g per minute. After 108 minutes the end of the reaction was indicated by the disappearance of the solid acid and by a sharp drop in the reaction temperature. Vacuum distillation of the product gave 797 g of isophthaloyl chloride (98 % based on the acid). The boiling point was ΙβΟ to 162 ° C at 25 mm. .

Example IV

A reactor tube was constructed from Pyrex glass tube (50 cm 'long) with an inner diameter of 62 mm, which was fused at both ends with tapered, ground glass outer connectors. There are corresponding caps constructed _y which were provided with internal connectors and that both in the bottom and provided at the top of the reactor tube encryption

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Fit bindings. The cap on the head was fitted with three ground glass connections to (1) provide an inlet for the supplied mixture, (2) an inlet for a thermometer and (3) an outlet for the gaseous reaction products result. The cap provided on the bottom was also provided with three external ground glass connections in order to be able to do this (1) an inlet for the phosgene gas, (2) an inlet for a thermometer and (3) an outlet for the liquid product stream to deliver. The entire reaction tube was controlled by means of a heating belt controlled by a regulating transformer was heated.

A slurry of 500 parts of liquefied isophthaloyl chloride, 200 parts of isophthalic acid and 3.0 parts of triethylamine were removed from a heated feed vessel at the top of the reactor fed at a rate of about 5 ^ 85 parts per minute. The mixture moved continuously downwards in the reactor and met the phosgene gas, which was in countercurrent rose continuously in the reactor at a rate of about 2.1 g per minute. The mean temperature of the reaction vessel was maintained at 150 ° C by suitable means of adjusting the tension on the heating belt. The liquid product was continuously withdrawn from the bottom of the reaction vessel at such a rate that the level of the reaction mixture inside the reaction vessel was essentially constant stayed. Periodically, the collected product was removed in vacuo, about 1/3 of the batch being distilled off. Of the Still bottoms were used to make a fresh feed mix. There were therefore 200 parts of isophthalic acid and 500 parts of the distillation residue with 0.05 parts of fresh triethylamine (by the amount caused by the mechanical transfer to replace any loss of catalyst) to form a further starting mixture, which is fed into the feed vessel was given. This process produced a total of 1200 g of isophthaloyl chloride within 10 hours of operation.

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Claims (6)

Claims 1. A process for the production of an acid chloride by reacting a carboxylic acid with carbonyl chloride at an elevated temperature, characterized in that the reaction is carried out in the presence of a tri-substituted tertiary Amine catalyst of the general formula Rf I
^R 3 where R., R _? and R ₇ . independently of one another from the group consisting of alkyl, aryl, cycloalkyl, alkaryl and aralkyl radicals are selected, with 1 to 25 carbon atoms / and ^ an acid chloride medium is carried out, the acid chloride medium corresponding to the acid chloride produced. 2. The method according to claim 1, characterized that the carboxylic acid is isophthalic acid .. 3. The method according to claim 1, characterized in that that the carboxylic acid is terephthalic acid 4. The method according to any one of the preceding claims, characterized in that the reaction temperature is 120 to 160 ° C. 5. The method according to any one of the preceding claims, characterized in that the catalyst is triethylamine. 2 7/1142 0! 8GINAt 240D007 6. The method according to any one of the preceding claims, characterized in that the tertiary amine in an amount of 0.1 mol-SS to about 2.0 mol-S? based on 1 mole of the carboxylic acid. 409827/1 142