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 p repared in an alkoxide-derived sol-gel process in the presence of poly(ethy lene oxide) (PEO) with an average molecular weight of 100000. In this proce ss, the interconnected macroporous morphology is formed when transitional s tructures of spinodal decomposition are frozen by the sol-gel transition of silica. The addition of nickel into a silica-PEO system has negligible eff ect on the morphology formation suggesting that phase separation in the nic kel-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 m esopores in the silica gel skeleton as fine particles rather than aggregate d in macropores. It is considered that PEO interacts with both silica and n ickel cations. The interaction between PEO and Ni makes nickel distribute i n the silica phase and keeps Ni from aggregation during drying, resulting i n a high dispersion of Ni.