Mechanocatalytic hydrogenolysis of benzyl phenyl ether over supported nickel catalysts

Abstract

Mechanocatalysis is a promising approach for green, solvent-free biomass deconstruction and valorization. Here, the hydrogenolysis of benzyl phenyl ether (BPE), a model lignin ether, via ball milling is demonstrated over supported nickel catalysts at nominally room temperature and atmospheric hydrogen pressure. The hydrogenolysis reaction network closely follows that of solution-based reactions, with the primary products being toluene, phenol, and cyclohexanol. The mechanical energy during milling not only drives the chemical reactions but also activates the nickel by exposing fresh metallic surfaces from passivated particles, which replaces a thermal activation step. The hydrogenolysis rate is shown to be largely insensitive to the final nickel particle size, but reactivity of the oxide support can be enhanced during milling which contributes to carbon deposition. This work demonstrates the underlying chemistry necessary for mild lignin depolymerization using reductive mechanocatalysis.