Catalytic deoxygenation of methyl laurate as a model compound to hydrocarbons on nickel phosphide catalysts: Remarkable support effect

This work investigated the support effect on the deoxygenation of methyl laurate to C11 and C12 hydrocarbons over nickel phosphide catalysts. By the H2-TPR method from the precursors with Ni/P ratio of 1.0, Ni2P was produced on SiO2, CeO2, TiO2 and SAPO-11, while Ni3P and Ni12P5 were formed on γ-Al2O3, and Ni12P5 and Ni2P were formed on HY. Ni2P/SiO2 had lower electron density of Ni site than other catalysts, where either there were the Ni3P and Ni12P5 phases or there was the electron transfer from reduced CeO2 or TiO2 to Ni2P. At 573-613 K and 3.0 MPa, the conversion of methyl laurate and the selectivity to C11 and C12 hydrocarbons tended to decrease in the sequence of Ni2P/SiO2 > Ni3P-Ni12P5/Al2O3 > Ni2P/TiO2 > Ni2P/SAPO-11 > Ni2P-Ni12P5/HY > Ni2P/CeO2, whereas the C11/C12 molar ratio followed in the order of Ni2P/CeO2 > Ni3P-Ni12P5/Al2O3 > Ni2P/SiO2 > Ni2P/SAPO-11 > Ni2P/TiO2 > Ni2P-Ni12P5/HY. The effect of supports mainly results from their acidity and reducibility. The catalyst activity, the selectivity to hydrocarbons and the deoxygenation pathway are correlated with the surface density of Ni site, the electron property of Ni site, the Ni2P crystallite size and the synergism between the Ni site and the acid site or the oxygen vacancy.