Efficient biodiesel production via solid superacid catalysis: a critical review on recent breakthrough
Biodiesel produced from triglycerides and/or free fatty acids (FFAs) by transesterification and esterification has attracted immense attention during the past decades as a biodegradable, renewable and sustainable fuel. Currently, the use of solid superacid catalysts has proved a more efficient and “green” approach due to avoidance of environmental and corrosion problems and reduced product purification procedures. However, it is less viable economically because the reusability is low due to the lack of a hydrophilic/hydrophobic balance in the reactions that involve the use of inedible feedstock with a high water content. Therefore, this study gives a critical review on recent strategies towards efficient and “green” production of biodiesel via solid superacid catalysis. The strategies discussed include alkyl-bridged organosilica moieties functionalized hybrid catalysis to improve the hydrothermal stability of superacid catalysts, pre- and in situ water removal, and process intensification via temperature profile reduction. The strategies enabled well-defined porosity and an excellent hydrophobicity/hydrophilicity balance, which suppressed deactivation by water and glycerol.