Catalytic disassembly of an organosolv lignin via hydrogen transfer from supercritical methanol

Abstract

A novel approach to disassembling biomass-derived lignin into processible units is described. This transformation is achieved in supercritical methanol, using a Cu-doped porous metal oxide as the catalyst, at a relatively mild temperature (300 °C). Hydrogen transfer from methanol to an organosolv lignin results in the complete hydrogenolysis of phenyl ether bonds, coupled with the hydrogenation of aromatic rings. The product is a complex mixture composed principally of monomeric substituted cyclohexyl derivatives with greatly reduced oxygen content and negligible aromatics. Notably, no char formation was observed. We also describe operational indices based on the 1H NMR spectra that facilitate holistic evaluation of the product distribution in this and other biomass transformations.