GB578751A - Process for the production of alkyl esters from fats and fatty oils - Google Patents

Abstract

Alkyl esters of fatty acids are prepared from fats and fatty oils containing free fatty acids by a process which comprises (a) treating the fat or fatty oil with an alcoholic solvent to dissolve the free acid and form a fatty acid and alcohol phase and a fatty glyceride and alcohol phase, (b) separating the two phases, and (c) reacting the fatty glyceride and alcohol phase with further alcohol and an alcoholysis catalyst under conditions adapted to bring about substantially complete alcoholysis both with the alcohol initially included in the phase and the alcohol subsequently added. The alcohol used in the extraction step (a) may be the same as that added in the alcoholysis step (c) and is preferably an aliphatic monohydric alcohol having from 1 to 6 carbon atoms in the molecule. The constituents of the fatty acid and alcohol phase may be reacted together in presence of an e terification catalyst and the alkyl esters of fatty acids thus obtained mixed with those obtained in step (c). Suitable fats or fatty oils are coconut, palm, olive, cottonseed, corn, tung, whale, fish and soyabean oils and tallow, while suitable alcohols are methyl, ethyl, propyl, isopropyl, the butyl, the amyl and benzyl alcohols. The presence of water may be tolerated in both the fat or fatty oil and the alcohol. Suitable alcoholysis catalysts are sodium hydroxide, methylate or carbonate, lime, boron trifluoride, aluminium chloride, glycerine sulphate, sulphuric acid, organic sulphonic acids and organic sulphonates, while suitable esterification catalysts are sulphuric acid, organic sulphonic acids, sodium hydroxide and sodium methylate. Where the alcoholysis catalyst is alkaline, the esterification catalyst may be acidic, or vice versa, so that when the two lots of alkyl esters are mixed, the catalysts partially neutralise each other. Various procedures are described for recovering glycerine and alkyl esters of fatty acids from the products of the alcoholysis and esterification reactions. In examples: (1) coconut oil containing free fatty acids is treated with methyl alcohol, the coconut oil glycerides-alcohol layer is subjected to alcoholysis with methyl alcohol in presence of caustic soda and the fatty acid-alcohol layer is allowed to esterify in presence of p sulphuric acid; (2) cottonseed oil containing free fatty acids is treated with methyl alcohol, the cottonseed oil glycerides-alcohol layer is subjected to alcoholysis with methyl alcohol in presence of sodium methylate and the fatty acid-alcohol layer is allowed to esterify in presence of phosphoric acid; and (3) tallow containing free fatty acids is treated with ethyl alcohol and the tallow glycerides-alcohol and fatty acid-alcohol layers processed in a manner similar to that of example (2). In each example it is stated that any partially reacted glycerides remaining at the end of the alcoholysis may be returned to be reworked with fresh glycerides and alcohol. The Specification as open to inspection under Sect. 91 describes the use of solvents other than alcohols to extract the fatty acids from the fats or fatty oils. Solvents mentioned are dioxane, Cellosolve, Carbitol, alkylamines such as trimethylamine and alkanolamines. This subject-matter does not appear in the Specification as accepted.