Catalytic Transfer Hydrogenolysis of Glycerol over Heterogeneous Catalysts: A Short Review on Mechanistic Studies.

Catalytic transfer hydrogenolysis, using liquid H-donors in the absence of pressurized H under mild temperatures, is regarded as the most important technology to substitute traditional hydrogenation processes in industry. Despite decade development with several breakthroughs in catalyst design, the reaction mechanism involved in H generation and subsequent hydrogenolysis reactions is still under debate. In this review, transfer hydrogenolysis of glycerol, as a representative example, on metallic catalysts is revised critically with respect to surface reaction mechanism and catalyst design. The detailed reaction pathways for propanol, methanol, formic acid and ethanol for H generation have been discussed systematically. In particular, reaction mechanism for catalytic C-H cleavage, H spillover/transfer and C-O cleavage reaction steps will be critically revised with experimental and theoretical results in literature. Insights into reaction pathways, mechanism and H transfer efficiency and structure-performance relation for Pd, Cu and Ni catalysts will be provided for future development of catalyst manufacture and process development. The outcome of this work is useful for successful implementation of bio-refinery.