CoZn/N-Doped porous carbon derived from bimetallic zeolite imidazolate framework/g-C3N4 for efficient hydrodeoxygenation of vanillin

Abstract

The development of non-noble metal catalysts with high efficiency for the hydrodeoxygenation (HDO) of bio-oil is of great importance for the utilization of lignin biomass resources. As a crucial lignin-based platform chemical, vanillin is a promising candidate for the production of fine chemicals and polymers. Here, a promising non-noble Co–Zn/NPC catalyst (NPC: nitrogen-doped porous carbon materials) for the HDO of vanillin was prepared by pyrolysis of Co–Zn zeolite imidazolate framework/graphitic carbon nitride (Co–Zn-ZIF/g-C₃N₄) composites. Full vanillin conversion with 99% MMP (2-methoxy-4-methylphenol) selectivity could be achieved at 100 °C and 1 MPa H₂ over 4Co–1Zn/NPC. Characterization results indicate that the presence of g-C₃N₄ promotes the formation of mesopores, which is beneficial for fast mass transfer. Additionally, the introduction of Zn downsizes the size of Co nanoparticles, and lowers the electron density around the Co atoms in Co–Zn/NPC catalysts, which can accelerate the hydrogenation of vanillin. More importantly, the Zn introduced in the catalyst may function as a basic site to facilitate the conversion of the intermediate HMP (4-hydroxy-3-methoxybenzyl alcohol) into MMP, thus enhancing the MMP selectivity. Moreover, Co–Zn/NPC presents excellent stability in the HDO reaction of vanillin. This work provides some useful insights into the design of novel non-noble metal catalysts with high efficiency for HDO of bio-oil.