Defective N, S Co-doped carbon sphere supported Pd catalyst for selective hydrodeoxygenation of biomass under mild conditions

Abstract

The development and design of high-performance catalysts for biomass hydrodeoxygenation (HDO) under mild reaction conditions is a treacherous challenge. A novel catalyst with low-load Pd supported on N, S co-doped carbon sphere (Pd/CNS) was synthesized for selective HDO of vanillin under mild conditions. The ratio of S, N doping is controllable by adjusting the amount of trithiocyanuric acid and 3-aminophenol precursors added (Pd/CNS-X, X = 0, 0.5, 1, 1.5). According to spectroscopic analysis, N/S doping leads to an increase in the intensity of Pd0/Pd2+, suggesting a remarkable correlation between the electronic structure of the Pd species and carbon support. The Pd/CNS (1) catalysts with S/N = 1 exhibit excellent catalyst activity with a > 99.6 % yield to 2-methoxy-4-methylphenol (MMP) at 50 ℃, superior to without sulfur doping catalyst under mild conditions. Further studies have shown that the coordinated effect of N/S contributes to the formation of electron-rich defect surfaces, which facilitates the stabilization of Pd nanoparticles, promotes the transfer of electrons from the surface to the Pd species and accelerates substrate adsorption. The optimal Pd/CNS(1) catalyst showed stable catalytic performance after being reused five times. The engineering of heteroatom doping on carbon materials offers a novel idea for the design of excellent catalysts to catalyze the conversion of various lignin derivatives.