Challenges and perspectives on using acidic ionic liquids for biodiesel production via reactive distillation

Biodiesel, known as a renewable fuel, is an environmentally friendly energy source derived from animal and vegetable oils, as well as recycled oil. Despite this, the current advancements in biodiesel technology face challenges in fully replacing petrochemical diesel, primarily due to the non-green catalytic synthesis and high production cost associated with biodiesel. Ionic liquids containing strong Lewis acids or BrOnsted acids have been highlighted as a novel class of environmentally friendly solvents and catalysts, showing green and effective catalytic potential in the synthesis of biodiesel via transesterification. In another aspect, reactive distillation technology could facilitate continuous forward reactions catalyzed by ionic liquids by swiftly removing reaction products from the reaction zone, offering advantages in improving the production efficiency, energy consumption, and cost reduction. From this perspective, we discuss the synthesis of biodiesel catalyzed by ionic liquids, supported ionic liquids, amphiphilic ionic liquids, and amphiphilic supported ionic liquids. The focus is on the process for synthesizing biodiesel through catalytic distillation. We emphasize the potential role of the lipophilic group in the ionic liquid catalyst, promoting the mutual solubility of the reactant triglyceride with methanol or ethanol. This enhancement might facilitate contact between the reactants and improve the catalytic efficiency of transesterification. Additionally, we propose several methods to improve the efficiency of biodiesel synthesis catalyzed by ionic liquid catalysts and suggest appropriate reactive distillation processes for biodiesel production.