GB606711A - Improvements in or relating to the treatment of fatty acids and of glyceride oils - Google Patents

Abstract

Esters of fatty acids with alcohols containing up to six carbon atoms are obtained from glyceride oils containing free fatty acids by first esterifying the acids with an alcohol of high boiling point and then subjecting the products to alcoholysis with an alcohol containing up to six carbon atoms. An alcohol of high boiling point is defined as one boiling at 195 DEG C. or above at atmospheric pressure, and specified alcohols of this kind are cetyl alcohol and polyhydric alcohols such as glycol or glycerol. However, if the original mixture contains mono- or di-glycerides as well as free fatty acids, addition of an alcohol of high boiling point may be dispensed with, provided that the number of unesterified hydroxy groups in the mixture is at least equivalent to the number of free carboxylic groups. Suitable conditions for the esterification and alcoholysis stages are indicated (see Group IV (b)). In an example, a mixture of hardened rape oil and fatty acids is heated with glycerol to 175-190 DEG C. in the presence of caustic soda, a stream of hydrogen under reduced pressure being passed through the mixture; the esterified mixture is then heated under reflex with absolute alcohol containing a little caustic soda, whereafter excess of alcohol is removed by distillation in a stream of hydrogen, the soap-containing glycerol layer is separated, and the residual layer of ethyl esters is washed with water and steam-distilled under reduced pressure.ALSO:Esters of fatty acids with alcohols containing up to six carbon atoms are prepared by first esterifying the acids with an alcohol of high boiling point and then subjecting the products to alcoholysis with an alcohol containing up to six carbon atoms; an alcohol of high boiling point is defined as one boiling at 195 DEG C. or above at atmospheric pressure. The process may be applied to fatty acids as such or to glyceride oils having a high content of free fatty acids (see Group III). Suitable alcohols of high boiling point are cetyl alcohol and polyhydric alcohols such as glycol or glycerol. Known catalysts may be present in both the esterification and alcoholysis stages, but preferably alkali hydroxides or alkali compounds of polyhydric alcohols, e.g. potassium glyceroxide, are used as alcoholysis catalysts. The alcohol used for alcoholysis should be anhydrous or very nearly so, and access of water to the mixture during alcoholysis should be prevented. In an example, a mixture of hardened rape oil and fatty acids is heated with glycerol to 175-190 DEG C. in the presence of caustic soda, a stream of hydrogen under reduced pressure being passed through the mixture; the esterified mixture is then heated under reflux with absolute alcohol containing a little caustic soda, whereafter excess of alcohol is removed by distillation in a stream of hydrogen, the soap-containing glycerol layer is separated, and the residual layer of ethyl esters is washed with water and steam - distilled under reduced pressure.