An effective process for esterification of free fatty acids (FFA) by Novozym 435 in expanded bed reactors was developed. Oleic acid and palm fatty acid distillate (PFAD) were used as FFA. In the circulated batch process, Novozym 435 was reusable for 22 cycles with an FFA conversion greater than 90%. Furthermore, in the continuous process using four expanded bed reactors connected in series, FFA conversions from the esterification of oleic acid and PFAD with a total residence time of 80 min were 93.5% and 88.5%, with the overall productivity of about 1000 g and 940 g fatty acid methyl ester (FAME) litre^-1 hr^-1, respectively.

Keywords: biodiesel, esterification, expanded bed reactor, palm fatty acid distillate