Role of ZrO2 crystal on the hydrodeoxygenation of methyl palmitate over NiMo/ZrO2 catalyst

Abstract

The hydrodeoxygenation of biomass into high-quality fuels is an effective strategy for solving the shortage of traditional fossil energy sources. In this paper, four NiMo/ZrO2 catalysts with different crystalline ZrO2 supports were synthesized and their catalytic properties for the hydrodeoxygenation of methyl palmitate were further investigated. Different crystalline ZrO2 exhibited different concentrations of oxygen vacancies, which could modulate the Ni valence state of NiMo/ZrO2 catalyst and affect adsorption and activation of CO bands, thus affecting catalyst activity and selectivity. Pure phase ZrO2, especially monoclinic ZrO2, was found to possess a stronger electron transfer capacity, a higher amount of Ni0 and oxygen vacancies on the surface than mixed phase ZrO2, which was conducive to dissociate H2 molecules and activate the CO bond. Thus, NiMo/m-ZrO2 (monoclinic phase) exhibited the highest hydrogenation conversion (99.5%) and liquid alkanes selectivity (96.7%, hexadecane: 68.8%) under relatively mild condition (240 °C, 3 MPa H2). In addition, the NiMo/m-ZrO2 catalyst maintained excellent catalytic stability without significant deactivation after continuous reaction for 86 h.