Heterogeneous Acid Catalysts for Biodiesel Production: Effect of Physicochemical Properties on Their Activity and Reusability

Replacing homogeneous acids with heterogeneous acids provides an appealing approach for biodiesel production due to their reusability and easy recycling. The physicochemical properties of heterogeneous acids have a significant influence on catalytic activity and reusability. Herein, the influence of physicochemical properties (i.e., acid density, acid strength, acid type, wettability, thermal sensitivity, and magnetism) on catalytic activity and recyclability is elaborately discussed. Characterization techniques for identifying physicochemical properties are elaborated. Methods for regulating physicochemical properties are summarized. Finally, the opportunities and challenges of heterogeneous acid use for biodiesel production are discussed. This review provides theoretical guidance for developing efficient and stable heterogeneous acid catalysts for biodiesel production by adjusting their physicochemical properties.