GB706712A - Process for the production of aliphatic ethers - Google Patents

Abstract

A mixture of saturated and unsaturated aliphatic ethers is produced by subjecting an acetal to decomposition at elevated temperature and at a pressure in the range 1-20 kg. per sq. in. The acetals used as starting materials are products of a reaction between aldehydes and alcohols. The acetals may be decomposed, if desired, by passing them over a porous material, for example, silica gel, aluminium oxide, kieselguhr or activated bleaching earths, as catalysts at a temperature in the range 250 DEG -350 DEG C. or may be decomposed without a catalyst, preferably by heating in fractionating columns at a temperature in the range 90 DEG -300 DEG C. The required acetal can be made, for example, by reacting one molecule of butyraldehyde with 2 molecules of butyl alcohol or by reacting propionaldehyde with a suitable alcohol with elimination of water. When decomposing the acetals a decomposition of 40-80 per cent. is desirable and the undecomposed residue may then be recycled with fresh acetal feedstock. When the acetal obtained from butyraldehyde and butyl alcohol is used as starting material the reaction mixture may contain, in addition to the ethers which are formed (dibutyl ether and butyl crotyl ether) butyl alcohol, butyraldehyde and crotonaldehyde: various methods of separating the components from the reaction mixture are given. Advantageously an amount of aldehyde is added to the reaction mixture after the decomposition of the acetal equivalent to the amount of alcohol present so that an addition of a condensation agent, preferably hydrochloric acid, acetals are formed which can be subjected to another decomposition process. In the examples (a) butyraldehyde and butyl alcohol are condensed in the presence of hydrochloric acid to give an acetal mixture which is decomposed by heating to give dibutyl ether and butyl crotyl ether; some butyraldehyde, crotonaldehyde and butyl alcohol are also formed; (b) an acetal mixture obtained as in (a) is heated and passed over silica gel to give a mixture of crotyl butyl ether and dibutyl ether in addition to some butyraldehyde, crotonaldehyde and butyl alcohol; and (c) the acetal mixture obtained as in (a) is heated to give a mixture of crotyl butyl ether, dibutyl ether, and butyl alcohol; the mixture is heated with more butyraldehyde and hydrochloric acid and condensed in two more stages to give a fraction which consists almost entirely of ethers.