Cyclic fatty acids: Removal of aromatic acids formed during hydrogenation

Abstract

Monomeric fatty acids derived from the alkali treatment of linseed oil at temperatures above 200C contain cyclic (1,2-disubstituted eyclohexadiene) and straight-chain fatty acids. Hydrogenation converts cyclic to liquid, saturated cyclic acids that can be recovered in a pure state by crystallization. During hydrogenation (palladium catalyst) some of the unsaturated cyclic acids form aromatic fatty acids by loss of hydrogen and under some conditions are not subsequently hydrogenated. It was necessary to establish conditions for complete hydrogenation since color and oxidative stability at high temperature are inversely related to aromatic content. Previously, tile preparation of cyclic acids free of aromatic acids was by hydrogenation in the presence of a high concentration of acetic acid. A further study of reaction variables established conditions to make Saturated cyclic fatty acids free of aromatic without acetic acid. Factors favoring the elimination of aromatic acids include a high catalyst concentration, high temperature and pressure, good hydrogen dispersion in the liquid and good agitation.

Identification of Aromatic Fatty Acids in Butter Fat

“…Different fatty acids with the aromatic moiety in the chain (terminal carbons in the ortho-position: 1, 2, 3, 4, 5, 6, 8) have been identified as artefacts of the industrial hydrogenation (with a palladium or nickel catalyst) of unsaturated cyclic acids derived from the alkali treatment of linseed oil at temperatures above 200°C [24,25,39,40]. Although these conditions were different to those occurring in the rumen of cows we could not fully rule out this opportunity, since the mass spectra of the methyl esters of some aromatic fatty acid artefacts published by Zeman et al were quite similar to the spectra recorded in our samples (they featured M ?…”

“…These have been described in plants of the aroid subfamily [16][17][18][19], Dracunculus vulgaris, i.e., a flowering plant in the family Araceae (in samples from Turkey, 13-phenyltridecanoic acid (Ph-13:0) was found to contribute about 10 % to the total fatty acids [20,21] ), in Brazilian plants of the Trichilia genus [22], as well as a bacterium (Vibrio alginolyticus) associated with the marine alga Cladophora coelothrix [23]. In addition, isomers with the phenyl unit in the acyl chain are formed as artefacts during the hydrogenation of plant oils [24][25][26][27]. Since this process is similar to the function of the rumen of cows, both structural variants of aromatic fatty acids could be the origin of the potentially aromatic fatty acids detected in the milk fat of a butter sample.…”

Potential synthetic lubricants: Diol ester of C18‐saturated cyclic acids

“…Cl~-Saturated cyclic acids (HCal) were prepared by alkaline isomerization of linseed oil in water solution according to the method of Beal et al (2). Hydrogenation of cyelized monomerie acids was carried out under conditions found to eliminate aromatic contaminants (3,5). The bulk of the straight-chain saturated acids (stearie and pahnitie) was removed by crystallization from acetone at -50C followed by eentrifugation.…”