CS216042B1 - Process for preparing benzyl alcohol - Google Patents

Abstract

The invention relates to a method for preparing benzyl alcohol; by hydrolysis of benzyl chloride with an aqueous solution of an alkali metal carbonate or hydroxide at elevated temperature or pressure. The unreacted benzyl chloride contained in the reaction mixture after hydrolysis catalyzes the dehydration of benzyl alcohol to benzyl ether during distillation. This reaction can be prevented by decomposition of the remaining benzyl chloride by the action of tertiary amines C8 to C10 or their salts.

Description

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A process for the preparation of benzyl alcohol

The invention relates to a process for the preparation of benzyl alcohol; by hydrolyzing the benzyl chloride with an aqueous solution, an alkali metal carbonate or hydroxide at elevated temperature or elevated pressure. The unreacted benzyl chloride contained in the reaction mixture after hydrolysis catalyses the dehydration of the benzyl alcohol to the benzyl ether during distillation. This reaction can be prevented by decomposition of the remaining benzyl chloride by treatment with tertiary amines C8 to or their salts.

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The invention relates to the preparation of benzyl alcohol by the hydrolysis of henzyl chloride with aqueous solutions of alkali metal carbonates or hydroxides.

In the hydrolysis of benzyl chloride, side reactions take place simultaneously, with the formation of benzyl ether and benzaldehyde in addition to the oenzyl alcohol, with some benzyl chloride remaining undetected in the reaction mixture. The production of benzyl alcohol by the hydrolysis of benzyl chloride is carried out in a batch reactor in a batch process and continuously in tubular and flow-through reactors. A disadvantage of the prior art processes for the preparation of benzyl alcohol by the hydrolysis of benzyl chloride is the formation of 7 to 12% by weight of benzyl ether, the use of which is considerably limited. Benzyl ether is formed during the hydrolysis itself and further fractions are formed in the separation of the reaction mixture by distillation, whereby thermal exposure occurs during which the unreacted benzyl chloride catalyses, in particular in the presence of metals, the dehydration of the benzyl alcohol to form the benzyl ether.

It has now been found that the benzyl ether vanity during distillation of the reaction mixture can be prevented by the method according to the invention, characterized in that it is treated with tertiary amines C 8 to their salts such as triethylbenzylammonium chloride to decompose unreacted benzyl chloride contained in the reaction mixture. or hexamethylenetetramine in an amount of 1 to 5 moles per 1 mol of benzyl chloride remaining.

The advantage of the process according to the invention over the original technological processes is that it avoids the formation of further proportions of benzyl ether in the distillation of the organic phase of the reaction mixture.

In order to elucidate the nature of the invention, examples are given below.

Example 1

A δ-liter sulfonation flask was charged with 655 S of 100% benzylchloride used previously to extract the aqueous phase from the previous operation, 543 g of calcined sodium carbonate and 3,300 g of water. After 13 hours under reflux while stirring and a temperature from 98 to 100 ^P C containing anhydrous organic phase of the reaction mixture of 1.9% by weight of benzyl chloride, 2.4 wt% of benzaldehyde, 8.1% benzyl ether benzyl alcohol and 86.7%. 40 g of hexamethylenetetramine are added to the reaction mixture and the mixture is heated to reflux with stirring for 1 1/2 ha. The flask is then cooled and the organic phase is separated. The aqueous phase ee is extracted twice with 200 g and once with 255 g of benzyl chloride for the next batch. After the organic phase is separated by vacuum distillation, 492 g of benzyl alcohol are obtained, 98.6%. 86.6% of theory, calculated on benzyl chloride. In addition, 26.0 g of an interfacre containing water, benzaldehyde and benzyl alcohol and 62 g of deet are obtained. a residue consisting predominantly of benayl ether and benzyl alcohol.

Example 2

Into the C 1 sulphonation flask, charge 655 g of benzyl chloride (calculated at 100%),

343 g of calcined sodium carbonate, 655 g of chlorobenzene and 3278 g of water. The reaction mixture was heated to 95 DEG-96 DEG C. under reflux for 13 hours under stirring with water.

The organic phase contains 0.94 wt. % benzyl chloride, 0.70 wt.%, benzaldehyde, 0.96 wt.

of benzyl ether and 38.1% benzyl alcohol. Then 24 g of hexamethylenetetramine are added to the reaction mixture and heated to reflux with stirring for 1.5 more. Cool the flask contents and separate ae

The organic and aqueous phases. The organic phase, which contains only traces of benzyl chloride, is separated by vacuum; distillation yielded 472 g of benzyl alcohol 98.7%, ie 83.4% of theory, calculated on benzyl chloride. About 95% of the chlorobenzene is recovered under laboratory conditions. In addition, 25 g of an intermediate fraction containing water, chlorobenzene, benzaldehyde and benzyl alcohol and 30.5 g of a distillation residue consisting predominantly of benzyl ether and benzyl alcohol are obtained.

Example 3

The procedure is the same as in Example 1, the decomposition of the remaining benzyl chloride. in the reaction mixture prior to distillation, 8 g of triethylbenzylammonium chloride were added. The yields are; within the range of the standard deviation identical to those given in example 1.

Claims (1)

SUBJECT OF THE INVENTION A process for the preparation of benzyl alcohol by hydrolysis of benzyl chloride with an aqueous solution of alkali metal carbonates or hydroxides at temperatures of 90 to 140 ° C at atmospheric or elevated pressure, characterized in that the reaction mixture is treated with tertiary amines Cg to decompose unreacted benzyl chloride. to ^C 15 or salts thereof such as triethylbenzylammonium chloride or hexamethylenetetramine in an amount of 1 to 5 moles per 1 mol of benzyl chloride remaining.