Post-treatment for high content of ethyl ester from esterification of palm fatty acid distillate

Abstract

Ethyl ester from palm fatty acid distillate is of interest as biodiesel. However, the standard biodiesel quality free fatty acid (FFA) content is hard to achieve due to reversible reactions at low FFA content. The post-treatment of ethyl ester (1.5 wt% FFA) by esterification was investigated using homogeneous catalysts or heterogeneous catalysts, and comparing the short-chain alcohols ethanol and methanol. An approximate equilibrium was attained more easily when using methanol or the heterogeneous catalysts, and the goal of 0.25 wt% FFA content was achieved. First-order reaction kinetics were postulated, and three alternative kinetic models were formulated for cases with large excess in some reactants. The simplest such model gave the forward rate constant as 13.32 which was higher than that of the reverse reaction. The water generated during esterification contributed with total initial water, which also was a key factor affecting the water balance.

Keywords

• post-treatment
• palm fatty acid distillate
• esterification
• ethyl ester
• kinetics