Optimization of the sulfuric acid-catalyzed estolide synthesis from oleic acid

• Published in: Journal of the American Oil Chemists' Society Vol. 74; no. 4; pp. 473 - 476
• Main Authors: Isbell, T.A, Frykman, H.B, Abbott, T.P, Lohr, J.E, Drozd, J.C
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 1997; Springer; Springer Nature B.V
• Subjects: Applied sciences; biodegradable products; Catalysts; Chemical synthesis; Estolide; estolides; Exact sciences and technology; fatty acid esters; High temperature; Oleic acid; oleic homopolymer; Oligomerization; Optimization; Organic polymers; Physicochemistry of polymers; Polycondensation; polyestolide; polymers; Preparation, kinetics, thermodynamics, mechanism and catalysts; Sulfuric acid; Vacuum; Self condensation; Oleic acid; Aliphatic polymer; Preparation; Ester polymer; Unsaturated fatty acid; Condensation polymerization; Acid catalysis; Oligomer; Sulfuric acid
• ISSN: 0003-021X; 1558-9331
• DOI: 10.1007/s11746-997-0109-x

The production of estolide from oleic acid with sulfuric acid as a catalyst was optimized for minimal acid concentration and temperature. Commercial oleic acid forms estolide optimally when reacted at 55°C with 5% vol/vol concentrated sulfuric acid for 24 h under vacuum. The extent of oligomerization was 1.2 estolide units under these reaction conditions. Temperature plays a critical role in the rate of estolide formation as well as in the overall yield, with higher temperatures providing faster rates but lower yields. The ratio of sulfuric acid to oleic acid equivalents also plays a role, where higher acid concentrations gave faster rates and higher yields of estolide. Vacuum had a minor effect on oligomerization and estolide yield.