Hydrogenolysis of guaiacol and lignin to phenols over Ni/Nb2O5HZSM-5 catalyst

Abstract

Selective hydrogenolysis of C_Ar-O bonds in lignin to produce aromatic compounds typically necessitates severe conditions. We developed a Ni/Nb₂O₅HZSM-5 catalyst that facilitates direct cleavage of guaiacol's aryl ether bonds at reduced temperatures (200 °C) and pressure (0.1 MPa H₂), achieving a conversion of 89.5 % with the selectivity of phenol at 81.7 %, while retaining its activity after five cycles. The Ni/Nb₂O₅HZSM-5 exhibits a higher yield of phenol (49.1 mmol_phenol·g_Ni⁻¹·h⁻¹), currently achieving the highest phenol yield among Ni-based catalysts. The addition of Nb₂O₅ enhances the dispersion of Ni and augments the effective surface area. In addition, the strong interaction of Nb with the HZSM-5 changed the electronic state of Nb and enhanced the resistance of the catalyst to high temperature and mechanical stress. Employing this catalyst for lignin depolymerization in an aqueous medium led to a 17.0 wt% yield of alkyl phenolic compounds. This approach represents an advancement in biomass resource conversion, circumventing the dependency on high-pressure and precious-metal catalysts, and signaling a new trajectory for sustainable biomass utilization in scientific research.