Preparation and characterization of MCM-41 and silica supported nickel boride catalysts

Ni-B/MCM-41 and Ni-B/SiO2 catalysts were prepared by low-temperature reduct ion of surface-adsorbed nickel chloride with ethanolic sodium borohydride s olution. XRD analysis showed that the MCM-41 framework of Ni-B/MCM-41 catal yst remained intact, while nitrogen adsorption-desorption study revealed un iform pore size distribution of the channel system. Thermal treatment of th is catalyst under nitrogen at 450 degreesC indicated the presence of a segr egated nickel phase on the surface of MCM-41. On amorphous silica, however, amorphous nickel boride alloy may have formed. As-synthesized Ni-B/MCM-41 is more susceptible to oxidation than Ni-B/SiO2 probably due to the smaller size of its alloy particles. This suggestion is also supported by the EXAF S results. The lower activity of Ni-B/MCM-41 catalyst than Ni-B/SiO2 in ben zene hydrogenation reaction probably reflects the lower reducibility of nic kel oxide phase than nickel boride alloy phase. (C) 2001 Elsevier Science B .V. All rights reserved.