Recent Advances in Magnetic Nanoparticle-Based Heterogeneous Catalysts for Efficient Biodiesel Production: A Review

Owing to the worldwide concentration on energy security, a recent trend of the energy mix is adopted by gradually replacing fossil fuels with other renewable energy sources. Biodiesel has emerged as a promising candidate. It is renewable, nontoxic, and biodegradable and can be a suitable choice for undertaking this energy issue. Biodiesel can be produced via various procedures, e.g., dilution, microemulsion, pyrolysis, and transesterification. The latter is the most utilized procedure given its effectiveness in which vegetable oils or animal fats and short-chain alcohols are allowed to react in the presence of a catalyst. Different oil feedstocks are identified including edible, nonedible, and algae-based biomass resources. Conventionally, homogeneous catalysts are generalized for biodiesel production because of their high catalytic activity and low cost, albeit, due to high wastewater generation during the purification process of the product, separation problems, and soap production, heterogeneous catalysts have emerged to overcome problems facing the homogeneous catalytic system. Of these, magnetic nanomaterials including magnetite and spinel ferrites are introduced. A literature survey is comprehended in this review concerning magnetic nanocatalysts, preparation methods, and applications. The economic lookout is portrayed by using magnetic catalysts as a future catalytic vision. Besides, the biodiesel's physicochemical properties including kinematic viscosity, density, cetane number, flash, pour, and cloud points are reviewed for its commercial utilization.