Renewable Tar-Derived Pd@Biocarbon For Mild And Efficient Selectively Hydrodeoxygenation Of Vanillin

As an inevitable harmful waste, biomass tar has always been considered as one of the challenges of biomass resource utilization. In this paper, biomass tar is used as the carbon source for the preparation of biocarbon with different activators in one pot. The Pd@biocarbon catalysts with low Pd loading were synthesized for hydrodeoxygenation (HDO) of vanillin in the presence of poly(methylhydrosiloxane) (PMHS) as the hydrogen donor, avoiding gaseous hydrogen and high temperature. The effects of different activators (KOH and K2FeO4) and carbonization temperature on the structure and catalytic performance of the as-prepared Pd@biocarbon catalysts were investigated in detail. The characterization results showed that Pd@BC-KFe-800 activated by K2FeO4 and carbonized at 800 degrees C had abundant surface acid groups and a high degree of graphitization. Further evaluation of the catalytic activity showed that Pd@BC-KFe-800 had the highest catalytic activity and can achieve 94.6% vanillin conversion at 65 degrees C for 2 h. The mechanism study indicated that the high HDO activity is attributed to the synergistic effect of the active metal Pd and biocarbon with surface acidic hydroxyl groups and the good graphitization structure. Compared with KOH, K2FeO4 can improve the graphitization degree of biocarbon and lead to catalysts with stronger acidity, providing more acid sites for the HDO of vanillin. Furthermore, the as-prepared Pd@BC-KFe-800 catalyst has shown favorable recyclability after four uses. These findings not only provide a new idea for the green treatment of waste biomass tar but also give a reference value for the HDO of bio-oil under mild conditions.