Oxidation of Glycerol to Lactic Acid by Gold on Acidified Alumina: A Kinetic and DFT Case Study

Abstract

The aim of this chapter is to present proposed kinetic and density functional theory (DFT) models for the selective oxidation of glycerol to various hydroxy-acids over an acidified Au/γ-Al 2 O 3 catalyst. Glycerol oxidation over gold-based catalysts to valueadded chemicals continues to attract attention worldwide. Both the kinetics and theoretical mechanisms of this reaction have been reported in the past. However, some of the reported kinetic data was possibly collected under mass transfer limitations. In this case study we demonstrate that if mass transfer is eliminated, a pseudo zero-order model can be fitted to the experimental data with a high degree of correlation. Furthermore, we propose a plausible mechanism of pyruvaldehyde (PA) isomerisation to lactic acid (LAC) over supported molybdenum Lewis acid sites as investigated with density functional theory (DFT) approach. A proposed DFT model suggested that the rate-limiting step in the isomerisation of PA to LAC, catalysed by a Mo Lewis acid-site, could be the dissociation of a proton from an adsorbed water molecule -the protonation step.

Enhancing the understanding of the glycerol to lactic acid reaction mechanism over AuPt/TiO2 under alkaline conditions

“…From the data presented in Table 1 . [28][29][30] However, it is well established that AuPt/TiO2 catalysts are substantially more active than monometallic Au catalysts for this reaction, 31 which could provide explanation for the lower activation energy observed in this study.…”