Metal Oxide/Sulphide-Based Nanocatalysts in Biodiesel Synthesis

The use of metallic oxides/sulphides as nanocatalyst for biodiesel production has become an attractive approach based on the high performance of this type of material with respect to the conventional homogeneous acid–base catalysis. These materials can be obtained from a variety of efficient methods, especially in chemical form, such as co-precipitation, sol–gel, hydrothermal synthesis, among others. The physicochemical properties of these materials are related to their catalytic activity, and various characterization methods such as SEM, TEM, FTIR, TGA, BET, TPD and XPS have been used to provide an insight into the structure–catalytic activity relationship. The application of these nanocatalysts in the transesterification reaction is broadly known and has been widely investigated with different types of triglyceride or fatty acid sources. Currently, the search for metal oxides/sulphides with higher catalytic activity continues and their resistance to deactivation, especially by leaching, is still being improved..