Heterogeneous esterification of glycerol by using a gold catalyst

Compared to conventional catalysts, such as Pt and Pd, Au catalysts perform better in alcohol oxidation reactions and are thus becoming progressively more important in that context. The production of biodiesel is increasing in the world, and this also means that there is a growing amount of glycerol being produced, which represents an abundant and inexpensive new raw material. It is necessary to purify this by-product, but processing of all the available glycerol cannot be achieved by the pharmaceutical industry alone, and hence other options must be found. The present investigation was performed to evaluate the transformation of glycerol using a Au catalyst in a methanol medium with atmospheric air as oxidant. The primary product of this esterification is methyl glycerate which can be further transformed into dimethyl tartronate and dimethyl mesoxalate. The effects of reaction temperature, air pressure, amount of catalyst, base content, reaction time, and reuse of the catalyst were analyzed and compared to provide a better understanding of the Au catalyst and the reaction itself. Use of 10 % (w/w) catalyst gave good results regarding final conversion (>75 %), selectivity toward the desired products, and yields.