Ni/SiO2 catalyst with hierarchical pore structure prepared by phase separation in sol-gel process

Silica-supported nickel catalysts with both macropores and mesopores were prepared in an alkoxide-derived sol-gel process in the presence of poly(ethylene oxide) (PEO) with an average molecular weight of 100000. In this process, the interconnected macroporous morphology is formed when transitional structures of spinodal decomposition are frozen by the sol-gel transition of silica. The addition of nickel into a silica-PEO system has negligible effect on the morphology formation suggesting that phase separation in the nickel-containing system proceeds by repulsive interaction between the solvent and PEO adsorbed on the silica, as observed in the system without nickel. In gel formation, it was found that the Ni was distributed selectively in mesopores in the silica gel skeleton as fine particles rather than aggregated in macropores. It is considered that PEO interacts with both silica and nickel cations. The interaction between PEO and Ni makes nickel distribute in the silica phase and keeps Ni from aggregation during drying, resulting in a high dispersion of Ni.