Selective cleavage of ether C-O bond in lignin-derived compounds over Ru system under different H-sources

Abstract

Selective hydrogenolysis, the aromatic ether C-O bonds under mild conditions, is crucial for the valorization of lignin. In this context, the effects of H2 and solvent on the hydrogenolysis of lignin model compounds over Ru catalysts were explored. With H2 as hydrogen donor, the Ru/AC exhibited the highest activity for converting lignin model compounds into monomeric compounds, whereas H2 led to low selectivity of aromatics. However, isopropanol was the good H-donor solvent, which could provide a large amount of active hydrogen to promote the cleavage of C-O bonds. Additionally, the yield of aromatics in isopropanol was higher than that under H2 atmosphere. It could be ascribed to the fact that isopropanol is the protic solvent which displays Lewis basicity, and is a good H-bond donor and a good H-bond acceptor. The higher electron-releasing inductive effect of isopropanol made it easier to provide active hydrogen. Based on the experiments, the mechanism of benzyl phenyl ether hydrogenolysis in H2 and isopropanol system was presented.