Infrared Investigations on Metal-Support Interactions in Ni-SiO 2 Catalyst Precursors: Role of Silica

Abstract

In a Ni-silica catalyst system prepared by the precipitation/deposition method the silica is reported to play a role in forming the {open_quotes}support{close_quotes} to nickel carbonate (or hydroxide) species. The support formed is identified as various types of nickel silicate species and also as the species comprising -Ni-O-Si- linkages. Further, the support is shown to (i) provide the definite porous structure to the catalyst and (ii) influence the reducibility of nickel species. Also, in nickel catalyst system prepared by impregnation method, formation of silicate species on surface and its influence on reduction of nickel and restriction in metal sintering is well established. However, the mechanism of silica conversion to support species and influence on metal dispersion, the formation of a definite porous network and catalytic activity in Ni-silica catalyst system prepared by precipitation is not well established. In this paper Ni-silica catalyst precursors were prepared by adding separate solutions of nickel sulfate and sodium carbonate simultaneously to the precipitation vessel containing a silica slurry as described by Nitta et al. and maintaining a SiO{sub 2}/Ni ratio of 0.5, precipitation temperature = 92{degrees}C, and pH = 8.5. 15 refs., 1 fig., 1 tab.