Catalytic transfer hydrogenolysis of C–O bonds in lignin model compounds without arene hydrogenation

The shortage of resources and the destruction of the environment have caused serious resource and environmental problems shared by all countries around the world. As a ubiquitous renewable resource, biomass has great prospects for replacing fossil energy and attracted attention from the society. The use of catalytic approach to transform biomass into high-value chemicals is an effective way to use biomass efficiently. In this work, Ni-supported catalysts has been developed for the selective cleavage of C–O bonds in lignin model compounds with 2-propanol as the hydrogen source solvent. Among these catalysts, it was indicated that zirconium phosphate (ZrP)-supported Ni catalysts were highly efficient and recyclable for alkyl-aryl ether (α-O-4 and β-O-4) cleavage in lignin model compounds. The further investigation demonstrated that the transfer hydrogenolysis of the C–O bond is highly selective, which afforded phenols and aromatics as dominant products without the products arising from hydrogenation of aromatic rings. Through a series of characterization of the catalyst, it was demonstrated that the medium strong acid sites of the ZrP support promoted the cleavage of alkyl-aryl ethers (α-O-4 and β-O-4), and Brønsted acid sites favored for achieving high selectivity toward C–O bond cleavage. Additionally, Ni(0) sites on the ZrP catalysts were responsible for the catalytic transfer hydrogenolysis.