Non-plasmonic Ni nanoparticles catalyzed visible light selective hydrogenolysis of aryl ethers in lignin under mild conditions

Abstract

Light-driven catalysis on catalytically versatile group VIII metals, which has been widely used in thermal catalysis, holds great potential in solar-to-chemical conversion. We report a novel photocatalysis process for the selective hydrogenolysis of aryl ethers in lignin on a heterogeneous catalyst of non-precious Ni nanoparticles supported on ZrO₂. Three aryl ether bonds in lignin were successfully cleaved under mild conditions with excellent conversion and good to excellent selectivity under visible light irradiation. We also used solar irradiation to demonstrate a significant reduction in the total energy consumption. The light irradiation excited interband transitions in Ni nanoparticles and the resultant energetic electrons enhanced the activity of reductive cleavage of the aryl ethers. Its application potential was illustrated by the depolymerization of dealkaline lignin to give a total monomer yield of 9.84 wt% with vanillin, guaiacol, and apocynin as the three major products.