Transesterification of Litsea cubeba kernel oil to biodiesel over zinc supported on zirconia heterogeneous catalysts

An effective approach for synthesizing green and sustainable biodiesel fuel from low-value vegetable oils has been explored. Herein, a series of catalysts of zinc supported on zirconia (xZn/ZrO2) were successfully synthesized, characterized, and applied for the production of biodiesel from Litsea cubeba kernel oil (LCKO) through the transesterification process. The results showed that the monoclinic phase structure of the prepared catalysts transformed to the more stable tetragonal phase structure after supporting different Zn loadings (≥5%). Compared with the pure ZrO2, the highly dispersed Zn species on the surface of xZn/ZrO2 could be divided into Zn oxide and ZnOH+, which could promote the transesterification of LCKO. Thus, the 7%Zn/ZrO2 catalyst exhibited the best catalytic activity of the LCKO conversion 82.5%, which was attributed to the positive effects of both the ZrO2 support and Zn species. Furthermore, the various reaction parameters (such as reaction time, stirring rate, nCH3OH:nLCKO, catalyst amount, and reaction temperature) were investigated systematically and optimized carefully. And a possible mechanism of the transesterification process catalyzed by Zn/ZrO2 catalysts was also proposed. Finally, the physical properties of the as-synthesized biodiesel accorded with the current international biodiesel standards.