Deoxygenation of Methyl Laurate as a Model Compound to Hydrocarbons on Ni2P/SiO2, Ni2P/MCM-41, and Ni2P/SBA-15 Catalysts with Different Dispersions

The deoxygenation of methyl laurate as a model compound to diesel-like hydrocarbons was performed on Ni2P/SiO2, Ni2P/MCM-41, and Ni2P/SBA-15 catalysts. The effect of Ni2P dispersion on the catalyst structure and performance was investigated. The average Ni2P crystallite sizes varying from 3 to 12 nm were obtained. In correlation with the Ni/P ratio, the catalyst acid amount was mainly determined by the surplus P species. The deoxygenation was tested at 300-340 degrees C, 2.0 MPa, weight hourly space velocity of 10 h(-1), and H-2/methyl laurate ratio of 50. For different catalysts, the conversion of methyl laurate followed the different sequence from the turnover frequency (TOF). The TOF increased with the Ni2P crystallite size. The lower TOF on smaller crystallites can be attributed to the stronger interaction between Ni and P. Both hydrodeoxygenation and decarbonylation pathways occurred on the Ni2P catalysts. As indicated by the ratio between n-undecane (n-C-11) and n-dodecane (n-C-12) being larger than 1.0, the main deoxygenation pathway was decarbonylation. We suggested that the deoxygenation pathway was affected by Bronsted acidity and Ni2P crystallite size (i.e., the interaction between the Ni and P atoms). The Bronsted acid sites because of P-OH groups and the Ni sites having less interaction with P favored the decarbonylation pathway. With an increasing reaction temperature, the conversion, the selectivity to n-C-11 and n-C-12, and the n-Cii/n-C-12 ratio increased. At 340 degrees C, the conversion and the selectivity to n-C-11 and n-C-12 on all Ni2P catalysts exceeded 97 and 99%, respectively.