Transesterification of soybean and castor oil with methanol and butanol using heterogeneous basic catalysts to obtain biodiesel

Abstract

This paper focuses on the preparation and characterization of CaO, MgO and ZnO, both bulk and supported on γ-Al2O3 and their catalytic activity in the transesterification of soybean oil and castor oil with methanol and butanol in order to produce biodiesel. XRD, SEM, CO2-adsorption followed by TGA and N2 adsorption have been employed to characterize the prepared catalysts. In supported catalysts, the presence of γ-Al2O3 improves alcohol dissociation on the superficial basic sites. The first step of the reaction mechanism is then favored (hydrogen abstraction). In the transesterification of castor oil with butanol, MgO/γ -Al2O3 and ZnO/γ-Al2O3 catalysts showed high yields to FABE (Fatty Acid Butyl Ester) (97% and 85%, respectively). These last catalysts constitute an efficient alternative for obtaining second-generation biodiesel, taking into account that castor oil is a nonedible source and butanol is an alcohol that can be obtained from biomass.