Widely Used Catalysts in Biodiesel Production: A Review
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An ever-increasing energy demand and environmental problems associated with exhaustible fossil fuels have led to the search for an alternative renewable source of energy. In this context, biodiesel has attracted attention worldwide as an alternative to fossil fuel for being renewable, non-toxic, biodegradable, carbon-neutral; hence eco-friendly. Despite homogeneous catalyst has its own merits, currently, much attention has been paid to chemically synthesize heterogeneous catalysts for biodiesel production as it can be tuned as per specific requirement, easily recovered, thus enhance reusability. Recently, biomass-derived heterogeneous catalysts have risen to the forefront of biodiesel productions because of their sustainable, economical and eco-friendly nature. Further, nano and bifunctional catalysts have emerged as a powerful catalyst largely due to their high surface area and potential to convert free fatty acids and triglycerides to biodiesel, respectively. This review highlighted the latest synthesis routes of various types of catalysts including acidic, basic, bifunctional and nanocatalysts derived from different chemicals as well as biomass. In addition, the impacts of different methods of preparation of catalysts on the yield of biodiesel are also discussed in details.