A Review on Heterogeneous Catalysts Containing Basic Active Sites for Biodiesel Production

Abstract

The production of biodiesel using transesterification has drawn significant scientific interest as a renewable and eco-friendly substitute for petroleum diesel. Among the catalytic systems studied, heterogeneous catalysts with basic active sites have emerged as leading candidates due to their high catalytic activity, ease of separation, and reusability. This review synthesizes findings from 54 studies published between 2015 and 2026, examining the role of basic active sites in the transesterification mechanism across alkaline earth metal oxides, mixed metal oxides, supported catalysts, waste-derived catalysts, hydrotalcites, zeolites, metal-organic frameworks, and nanostructured materials. Catalytic performance is governed largely by surface area, pore structure, and the density, strength, and accessibility of basic active sites. CaO-based catalysts remain the most widely studied, reporting biodiesel yields above 90% under optimized conditions owing to strong basicity and low cost, though they remain susceptible to deactivation via carbonation and hydration.Waste-derived catalysts offer sustainable, low-cost alternatives, while mixed-metal and doped systems show improved stability, retaining activity over multiple reaction cycles depending on catalyst type.Despite these advances, large-scale application remains constrained by feedstock quality, active-species leaching, and catalyst deactivation. Future research should prioritize highly stable, reusable, and cost-effective catalysts with improved basic-site accessibility, alongside standardized reporting of reaction conditions to enable meaningful comparison across studies.