Variables affecting the yields of fatty esters from transesterified vegetable oils

TLDR

Transesterification yield and purity of fatty esters from cottonseed, peanut, soybean, and sunflower oils depend on alcohol‑to‑oil molar ratio, catalyst type (alkaline versus acidic), temperature, and oil refinement level. Alkaline catalysts (NaOH or methoxide) achieve near‑complete conversion of refined oils within 1 hr at ≥60 °C and ≥6:1 molar ratio, while at 32 °C 99 % conversion takes ~4 hr; acid catalysis is much slower, and crude oils give lower yields because of gums and impurities.

Abstract

Abstract Transesterification reaction variables that affect yield and purity of the product esters from cottonseed, peanut, soybean and sunflower oils include molar ratio of alcohol to vegetable oil, type of catalyst (alkaline vs acidic), temperature and degree of refinement of the vegetable oil. With alkaline catalysts (either sodium hydroxide or methoxide), temperatures of 60 C or higher, molar ratios of at least 6 to 1 and with fully refined oils, conversion to methyl, ethyl and butyl esters was essentially complete in 1 hr. At moderate temperatures (32 C), vegetable oils were 99% transesterified in ca. 4 hr with an alkaline catalyst. Transesterification by acid catalysis was much slower than by alkali catalysis. Although the crude oils could be transesterified, ester yields were reduced because of gums and extraneous material present in the crude oils.