Mixed metal oxides derived from layered double hydroxide as catalysts for biodiesel production

Demand for energy has increased globally due to population growth and socioeconomic development stemming from rapid industrialization and urbanization. This scenario worsens the dependence on energy resources and highlights the question regarding their availability, showing the fragility of non-renewable fossil fuels. In order to supply the growing world demand for energy and respond to environmental concerns, biodiesel was adopted as a mitigating solution to the problems arising from the burning of fossil fuels as it has a biodegradable, renewable and non-toxic character. Recently, many studies have given attention to the heterogeneous catalysts for the production of biodiesel, since some economic and technological problems were recognized in the production via homogeneous reaction. Among the studied catalysts, layered double hydroxides (LDH) have stood out for presenting adjustable properties according to the composition and methods of synthesis, which are directly associated with the structural, morphological and catalytic aspects of their oxides. This review article aims to elucidate the relationship between the structure, basicity, composition and catalytic activity of metal mixed oxides (MMOs) from LDHs. In addition, a comprehensive description is made of the advantages of using MMOs/ LDH-based catalysts, of the reaction optimization parameters and of the regeneration and reuse processes of these minerals.