Advances in Understanding the Selective Hydrogenolysis of Biomass Derivatives

Biomass has attracted great attention as an alternative to petrochemicals for the production of valuable chemicals and fuels. Hydrogenolysis reactions over heterogeneous catalysts offer pathways to upgrade renewable compounds to a variety of building block molecules; however, similarities among the functional groups in these reactants frequently limit the selectivity of these reactions. Consequently, a fundamental understanding of how oxygenates adsorb, activate, and react upon solid surfaces is essential for catalyst design and reaction engineering. In this Perspective, we describe significant advances in knowledge of the reaction networks and mechanisms, key reactive intermediates, and active site motifs that allow for the selective production of desired compounds by hydrogenolysis over heterogeneous catalysts. These insights draw from the mechanistic understanding gained from comparisons between kinetic measurements, in situ characterization of catalysts and organic intermediates, and ab initio calculations. Drawing from detailed insight taken from a century of study into reactions of hydrogen with hydrocarbons, we discuss the molecular similarities between reactions that cleave C-O and C-C bonds during hydrogenolysis of biomass-derived compounds that range from simple (e.g., alcohols) to polyfunctional molecules (e.g., guaiacol) on monometallic, bimetallic, and nonmetallic catalysts. Finally, we describe current challenges and opportunities for future research into hydrogenolysis reactions.