Support and pretreatment effects on the hydrotreating activity of SBA-15 and CMK-5 supported nickel phosphide catalysts

Ni2P and Ni12P5 containing catalysts were prepared by impregnation of the oxidic precursors on a SBA-15 mesoporous silica or on a CMK-5 nanoporous carbon. Three different kinds of precursors (calcined SBA, not calcined SBA and CMK) were reduced in hydrogen gas stream. X-ray diffraction (XRD) and 31P solid-state nuclear magnetic resonance (NMR) analysis of the passivated catalysts confirmed the presence of Ni2P and Ni12P5 in all materials prepared from oxidic precursors with initial molar ratio of P/Ni = 2.0 and 0.5, respectively. A mixture of Ni12P5 and Ni2P was found in the CMK-5 supported catalyst prepared with initial molar ratio of P/Ni = 0.5. Lower HDS and higher HDN steady state reaction rate constants were shown over the SBA-15 supported phosphide catalysts than over a commercial presulfided NiMo/Al2O3 reference catalyst. The activities with low (P/Ni = 0.5) initial P excess are always higher than those with high (P/Ni = 2) initial P excess. The ratios of HDN over HDS activities are much higher over all phosphide catalysts than over the NiMo reference sample. Higher catalytic activities were found on the silica than on the carbon supported catalysts. The impregnated SBA-15 supported samples were calcined or not before reduction, but it had no effect on the activities. The Ni12P5 containing SBA-15 supported catalysts always exhibited higher hydrotreating activities than the Ni2P active phase containing ones due to the higher dispersion of the former.