Biodiesel production from Jatropha curcas crude oil using ZnO/SiO2 photocatalyst for free fatty acids esterification

Abstract We report the production of biodiesel from Mexican Jatropha Curcas crude oil (JCCO) by a two step catalytic process. The high content of free fatty acids (FFA) present in JCCO was first esterified with methanol by a photocatalytic process under UV irradiation using ZnO/SiO2 as the heterogeneous photocatalyst. The solid catalyst was found to be highly active for the heterogeneous photocatalyic esterification of FFA with methanol. The activity of the solid catalyst remained unchanged even after 10 esterification runs, indicating that the heterogeneous photocatalysis is a viable option for FFA esterification reactions for biodiesel production. Transesterification step was catalyzed by NaOH through thermal activation process. Produced biodiesel fulfills all the international requirements for its utilization as a fuel. A probable reaction mechanism for the esterification process is proposed considering the generation of H+, CH3O· and R-COOH on the photocatalyst surface.