Selective hydrogenation in the preparation of purified oleic acid from animal fats. Elimination of extremely low crystallization temperatures

Abstract

A procedure is described by which a product containing at least 95% oleic acid can be prepared from animal fats. In this process crystallization of the oleic acid itself is not required, and therefore temperatures below−20°C. are not necessary. This constitutes a decided improvement over previously described processes, which require much lower temperatures. In this procedure the fatty acids, obtained by hydrolysis of inedible tallow or grease which has been selectively hydrogenated until its content of polyunsaturates is less than 1%, are crystallized from acetone at temperatures from 0° to −20°C. to precipitate the solid acids. These acids, which amount to about 50% of the starting material, are equivalent to “double- or triple-pressed stearic acid.” The liquid acids obtained from the filtrate usually contain 90% oleic acid and when fractionally distilled yield a product containing at least 95% oleic acid. Evidence is presented to show that this purified product contains isomeric oleic acids, although cis-9,10-octadecenoic acid undoubtedly predominates. The purified oleic acid is odorless and ranges from colorless to pale yellow, depending upon the quality of the starting material. In addition, it has remarkable color and odor stability. This suggests its use where these quelities are especially desirable, such as in many applications in the textile industry, in cosmetics and in pharmaceuticals. Also, these purified products would be more suited for use as chemical intermediates than the oleic acid (red oil) commercially available at present.