Hydrodeoxygenation of Methyl Palmitate over Supported Ni Catalysts for Diesel-like Fuel Production

Catalytic hydrodeoxygenation (HDO) of vegetable oils to renewable alkane-type biofuels has attracted more and more concern in recent years. However, the presently used catalysts were mainly focused on the sulfided CoMo and NiMo catalysts, which inevitably posed sulfur contamination in final products. Therefore, exploring nonsulfured catalyst for this processing is of fundamental importance, but it is still an open challenge. In this paper, we prepared the sulfur free Ni supported on SiO2, gamma-Al2O3, SAPO-11, HZSM-5, and HY by incipient wetness impregnation and tested the catalytic performance in HDO of methyl palmitate. Alkanes with long carbon chains were mainly produced with two possibly parallel approaches: hydrogenation of hexadecanal to hexadecanol, followed by dehydration/hydrogenation to C-16 alkane and decarbonylaton/decarboxylation of hexadecanoic acid to C-15 alkane. The acidity of catalysts significantly influenced their catalytic performance, and the Ni/SAPO-11 catalysts with weak and medium acidity showed superior properties to the other catalysts due to the synergistic effect of metal Ni and acidic support. The maximum yield of 93% for C15+ alkanes was observed over 7 wt % Ni/SAPO-11 under the mild reaction conditions of 493 K and 2 MPa, indicating its promising application in this reaction.