Transesterification for biodiesel production catalyzed by combined lipases: Optimization and kinetics

Abstract

Abstract Preparation of biodiesel from waste cooking oil catalyzed by combined lipases in tert ‐butanol medium was investigated. Several crucial parameters affecting biodiesel yield were optimized by response surface methodology, such as dosage of combined lipases of Novozym 435 and Lipozyme TLIM, weight ratio of Novozym 435 to Lipozyme TLIM, amount of tert ‐butanol, reaction temperature, and molar ratio of oil to methanol. Under the optimized conditions, the highest biodiesel yield was up to 83.5% The proposed model on biodiesel yield had a satisfactory coefficient of R 2 (= 94.02%), and was experimentally verified. The combined lipases exhibited high‐operational stability. After 30 cycles (300 h) successively, the activity of combined lipases maintained 85% of its original activity. A reaction kinetic model was proposed to describe the system and deduced to be a pseudo‐first‐order reaction, and the calculated activation energy was 51.71 kJ/mol. © 2009 American Institute of Chemical Engineers AIChE J, 2010