Halloysite as an Effective Nano-clay for Oxidative Depolymerization of Lignin to Phenolic Monomer

Abstract The catalytic activity of halloysite was evaluated for the depolymerization of lignin into phenolic monomers, with vanillin identified as the predominant component in the resulting bio-oil. Under optimal conditions, the total conversion of lignin reached up to 51%, of which vanillin accounted for 45.38 ± 1.29 mg/g with ~85% selectivity. Halloysite, a readily available and cost-effective clay, demonstrated remarkable catalytic efficiency, attributed to the synergistic effect between halloysite and hexafluoroisopropanol (HFIP). These findings highlight the potential of halloysite as an effective catalyst for the sustainable conversion of lignin into value-added monophenols.