Density Functional study on the transesterification of triacetin assisted by cooperative weak interactions via a gold heterogeneous catalyst: Insights into Biodiesel production mechanisms

Abstract

A Density Functional study predicting a heterogeneous-catalyzed reaction giving rise to biodiesel, was performed. Triacetin was used as a model of triglyceride in the presence of an Au(111) surface as the heterogeneous catalyst substrate. Explicit methoxy molecules were implemented as an alcohol solvent to understand the reaction trajectory along the well known three-step transesterification process. It was found that the reactants and products in the three-step processes are adsorbed to the Au substrate through non-covalent interactions of the electrostatic-type, which are also mediated by a van der Waals attraction. The density of states indicate that the electronic structure nature of Au is preserved after the interaction with the organic moieties. This may be addressed to an enhanced stability of the Au(111) catalyst through the overall reaction. A charge transfer analysis also reveals that the Au surface oxidation is also responsible for the transesterification of triacetin and evidences that molecular gold plays an important role in this catalytic process. Such results may provide fundamental insights into the design of heterogeneous catalysts for biodiesel production.