Cobalt Silicide Nanoparticles in Mesoporous Silica as Efficient Naphthalene Hydrogenation Catalysts by Chemical Vapor Deposition

Cobalt silicide nanoparticles in mesoporous silica SBA-15 were successfully prepared by metal-organic chemical vapor deposition of a single-source precursor and were characterized by nitrogen physorption, X-ray diffraction, temperature-programmed reduction, temperature-programmed desorption, and transmission electron microscopy. The catalytic hydrogenation of naphthalene on the cobalt silicide nanoparticles in mesoporous silica was investigated in a fixed-bed reactor at 340 °C under 4.0 MPa hydrogen pressure. No cobalt silicide was observed in the mesoporous silica without calcination because of the hydrolysis of Co(SiCl 3 )(CO) 4 . Highly dispersed and evenly distributed cobalt silicide particles with diameters of 2−4 nm could be formed by adsorption and reduction of Co(SiCl 3 )(CO) 4 in the mesoporous silica with calcination above 500 °C. The cobalt silicide loading in the mesoporous silica depended on both the amount of precursor provided and the amount of hydroxyl groups in the mesoporous silica. A 8.3% CoSi/SBA-15 sample showed lower conversion and higher selectivity to tetralin (about 100%) in the naphthalene hydrogenation, while a 16.1% CoSi/SBA-15 sample showed a higher catalytic activity up to 87% and a lower selectivity to tetralin (35%) than other CoSi/SBA-15 samples, which may be due to the size effect and the strong interaction of CoSi and support.