Recent advances in heterogeneous catalysis for green biodiesel production by transesterification

Heterogeneous catalysis has provided a viable alternative to homogeneous catalysis for the production of low-cost biodiesel fuel, overcoming the constraints of homogeneous catalysis. In recent years, there have been numerous breakthroughs in the development of high-efficiency and cost-effective heterogeneous-based catalysts for catalytic transesterification of triglycerides (oil or fat) to biodiesel. Because of its simplicity and low cost, the heterogeneously catalyzed transesterification reaction has long been considered the most feasible biodiesel synthesis method. The intrinsic features of nine types of heterogeneous catalysts, including heteropolyacid, zeolite, hydrotalcite, carbon and waste materials, metal, metal oxide, enzyme, and ion exchange resins, which are commonly used in today's biodiesel research, have been studied in detail. Emphasis is placed on versatile catalysts with high-activity and low production cost as they make biodiesel production more practical, efficient and sustainable. Key parameters that influence the activity of heterogeneous catalysts as well as challenges and opportunities that could motivate future exploration are also highlighted.