Molybdenum modified nickel phyllosilicates as a high performance bifunctional catalyst for deoxygenation of methyl palmitate to alkanes under mild conditions

Abstract

Deoxygenation is the central challenge in converting bio-derived fatty esters into diesel-range hydrocarbons. A new molybdenum oxide doping nickel phyllosilicate (Mo–Ni@PSi) bifunctional catalyst was synthesized and used for the deoxygenation of methyl palmitate. Compared to impregnated Ni catalysts, Mo–Ni@PSi catalysts showed obviously enhanced catalytic activity for the deoxygenation process. Several structural variations induced by the introduction of Mo species were confirmed by H₂-TPR, XRD, FT-IR, TEM, XPS, and NH₃-TPD characterization. With these variations, more dispersive Ni nanoparticles (Ni NPs) and acidic sites were explored over the surface of modified Mo–Ni@PSi, which provided high catalytic activity for the deoxygenation of fatty esters. Furthermore, the content of the Mo element and the influences of activation temperature on the catalyst were also investigated. Remarkably, the highest catalytic activity was observed over the 3% Mo–Ni@PSi(B) catalyst with 98.3% yield of hydrocarbons at 220 °C and 1.0 MPa H₂, and the catalytic activity decreased with further increase in the Mo content. Then, hydrodeoxygenation and decarbonylation processes were both confirmed in the reaction mechanism study. Additionally, the catalyst also presented good catalytic activity after four recycle reactions. The oxidization of reduced Ni and Mo species was probably the main reason for the deactivation of the catalyst.