New Catalysts for Biodiesel Production under Supercritical Conditions of Alcohols: A Comprehensive Review

Nowadays, due to detrimental carbon dioxide emissions and dwindling non-renewable fossil energy from crude oil, biodiesel from green sources such as vegetable oils, animal fats, waste oils and microbial oils have been described as a promising non-fossil fuel, renewable, sustainable, clean, and biodegradable. So far, transesterification is the most superior process for converting green resources into biodiesel by reacting with alcohol in the presence of a catalyst. This process is influenced by some considerations such as alcohol to oil molar ratio, reaction temperature, reaction pressure, reaction time and specifically the amount of catalyst, which greatly affect the reaction performance and the biodiesel production. In depth, this review will discuss novel catalysts for biodiesel production under supercritical methanol and ethanol conditions by reviewing published articles related to this field to date.