Direct Nonoxidative Conversion of Methane to Higher Hydrocarbons over Silica-Supported Nickel Phosphide Catalyst

The direct dehydrogenative conversion of methane (DCM) to higher hydrocarbons has attracted much attention, because of the efficient utilization of natural gas. Ni catalysis of activation of C-H bonds of methane to H-2 and C is well-known. We have tried to control the catalysis of Ni via the addition of second elements and found silica-supported nickel phosphide (Ni-P/SiO2) materials as active catalysts for the DCM reaction at 1173 K. The products included C2H4 (ethylene), C2H6 (ethane), C2H2 (acetylene), C3H6 (propylene), C6H6 (benzene), C7H8 (toluene), and C10H8 (naphthalene). The formation of Ni2P on silica was determined using scanning electron microscopy and X-ray diffraction. Pure Ni2P material without support showed a fine catalytic activity for the DCM reaction. Almost the same activation energies of the Ni2P (249 kJ mol(-1)) and Ni-P/SiO2 catalysts (251 kJ mol(-1)) were obtained in the conversion rate of methane, which were lower than that of SiO2 (365 kJ mol(-1)). This indicated that Ni2P was the activate phase for the DCM reaction. The Ni2P phase activates C-H bonds of methane and converts to ethane. Other higher hydrocarbons were produced from ethane in the gas phase at 1173 K.