Pore structure control in Ni/SiO_2 catalysts with both macropores and mesopores

摘要

Ni/SiO_2 catalysts with bimodal pore structure were prepared by the sol-gel method of silicon tetraethoxide and nickel nitrate in the presence of poly(ethylene oxide)(PEO)and urea.The presence of PEO was effective to induce phase separation during the sol-gel process,and through-macropores interconnected three-dimensionally were formed by fixing transitional structure of the phase separation.After gelation,the as-prepared wet gel was aged at 80 deg C for decomposition of urea in order to increase pH of the solution within the gel.This pH increase led both the ripening of silica gel network through dissolution-reprecipitation and homogeneous deposition of nickel hydroxide.As a result,Ni could be dispersed highly in the silica network.In addition to the high dispersion of Ni,thus prepared Ni/SiO_2 has typical bimodal pore structure with size-controllable macropores and mesopores.The bimodal porous Ni/SiO_2 also had high thermal stability and showed steady catalytic activity in CO_2-reforming of methane at 700 deg C.