Simultaneous transesterification and esterification of unrefined or waste oils over ZnO-La2O3 catalysts

A single-step method was developed for biodiesel production from unrefined or waste oils using a series of heterogeneous zinc and lanthanum mixed oxides. Effects of metal oxide molar ratio, free fatty acids (FFA) and water content in feedstock, molar ratio of methanol and oil, and reaction temperature on the yield of biodiesel were investigated. A strong interaction between Zn and La species was observed with enhanced catalyst activities. Lanthanum promoted zinc oxide distribution, and increased the surface acid and base sites. The catalyst with 3:1 ratio of zinc to lanthanum was found to simultaneously catalyze the oil transesterification and fatty acid esterification reactions, while minimizing oil and biodiesel hydrolysis. A reaction temperature window of 170-220 degrees C was found for the biodiesel formation. A high yield (96%) of fatty acid methyl esters (FAME) was obtained within 3 h even using unrefined or waste oils. Published by Elsevier B.V.