Increased yields of saturated cyclic fatty acids which are fluid at 蜢50C have been obtained from linseed oil. Depending on reaction conditions, yields varied from 20舑42 g of cyclic acids per 100 g of linseed oil. Solvent ratios of 6, 3, and 1.5蝘1; catalyst concentrations of 10, 30, 60, and 100%; and reaction temps of 225, 275, 295, and 325C were evaluated. Ethylene glycol and diethylene glycol were compared as reaction solvents.In general, high solvent ratios favored high cyclic acid yields at the lower reaction temperature, but as the temperature increased the effect of solvent ratio decreased. Increasing the percentage excess of sodium hydroxide increased the cyclic acid yield. Diethylene glycol gave higher yields than ethylene glycol at comparable conditions.

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.

A method is described to determine cyclic fatty acids in cyclic monomers by gas-liquid chromatography (GLC), which separates saturated s'traight-ehain esters from cyclic esters. The content of cyclic esters can be determined by integration of the area on the chromatograph under the cyclic peaks. GLC was applied to cyclic monomers made from linseed oil and fronl linolenic acid. Samples of both hydrogenated and nonhydrogenated cyclic monomers were analyzed ; however, more reliable results were obtained on the hydrogenated samples. The results show a standard deviation of 0.25 for linseed oil and 0.36 for linolenic acid.Accuracy of the analysis was established by comparing data with that obtained by crystallization. The GLC method is approximately three times faster.

A mixture containing 37% cyclic and 63% straight‐chain fatty acids, made by high‐temperature treatment of linseed oil fatty acids with alkali, was separated by the urea adduct method to give unsaturated cyclic fatty acids (nonadduct) in 95% purity and 90–95% yeild. Previous reports from this Laboratory describe a process for separating cyclic fatty acids from stearic acid by hydrogenation followed by crystallization at −40C. The urea adduct method avoids hydrogenation and low‐temperature crystallization, and furthermore, unsaturated cyclic and unsaturated straight‐chain products can be recovered as individual fractions. Then, by readducting the unsaturated straight‐chain fatty acid fraction, the small amounts of palmitic and stearic acids are removed leaving an unsaturated fraction containing oleic, nonconjugated and conjugated linoleic and some unsaturated cyclic fatty acids.

Linolenic acid of more than 95% purity was produced by liquid‐liquid extraction of linseed oil fatty acids with wet furfural and hexane in a Podbielniak centrifugal extractor. The minimum ratio of furfural to linseed acids to obtain this purity was 10 to 1. There was no significant change in product purity for solvent ratios between 10 and 15, operating temperatures from 90Ŷ to 110ŶF., and furfural moisture contents between 1.0 and 2.8%. When the solvent ratio is reduced to 8 or the furfural moisture to 0.2%, purity decreases. Oxidation of linseed acids before extraction also results in decreased separation. An estimate based on pilotplant data indicates a 舠cost to make舡 (excluding administrative and selling expenses, profit, income taxes, and interest on investment) of 18.0 cents per pound of 97% linolenic acid for a process which includes hydrolyzing linseed oil, separating the fatty acids by liquid‐liquid extraction, recovering solvents by distillation, and distilling the fatty acid products. Potential uses for linolenic acid are reviewed.