Production, chemistry, and commercial applications of various chemicals from castor oil

Abstract

The presence of a hydroxyl group, in addition to an olefinic linkage, in the predominating fatty acid of castor oil gives this vegetable oil many unique and interesting properties. Castor oil consists largely of glycerides of ricinoleic acid or 12‐hydroxy octadecenoic acid. The chemical reactions of castor oil, undecylenic acid, 12‐hydroxylstearic acid, sebacic acid, and nylon 11, depict the uniqueness of this agricultural oil. By dehydration, castor oil is converted to a conjugated acid oil similar to tung or oiticica oil. The catalytic dehydration results in the formation of a new double bond in the fatty acid chain. The dehydrated castor oil imparts good flexibility, rapid dry, excellent color retention, and water resistance to protective coatings. The pyrolysis of castor oil cleaves the molecule to produce undecylenic acid and heptaldehyde. The pyrolysis of the methyl ester at 450–550 C results in the formation of methyl 10‐undecylenate. Hydrolysis of the methyl ester gives 10‐undecylenic acid. Hydrogen bromide is added to form 11‐bromo undecanoic, which is ammoniated and condensed to form a nylon polymer. When castor oil is added slowly to an 80% caustic solution, the sodium ricinoleate formed splits to form sodium sebacate and capryl alcohol. Sebacic acid is condensed with hexamethylene diamine to form nylon 6,10. The commercial application of castor oil derivatives in urethanes, starch gel modifiers, medium chain triglycerides, and thixotropic additives is reviewed briefly.