Synthesis of mesoporous Ni-La-Si mixed oxides for CO2 reforming of CH4 with a high H2 selectivity

Ni-La-Si mixed oxides with different La loadings were first synthesized through one-step polyethylene glycol-assisted hydrolysis of tetraethoxysilane and inorganic salts in a water-ethylene glycol solution of nitric acid. The Ni-La-Si materials exhibited mesoporous structures with narrow pore size distributions and large specific surface areas. Effects of La loadings on material structure, surface properties, interaction between Ni species and supports, and dispersion of Ni species were discussed in detail. Homogeneously-dispersed NiO species were reduced in situ with H-2 to form ultrafine metallic Ni nanocrystallites of 5-7 nm throughout the mesoporous silica. The obtained Ni/La-Si catalysts were applied for CO2 reforming of CH4 and exhibited high catalytic activity and excellent anti-coking ability. Addition of La in the Ni-La-Si catalysts not only enhance dispersion of Ni crystallites, reforming rate of Ni sites and catalytic stability, and more importantly, but also strongly inhibited reverse water gas shift reaction, resulting in almost 100% selectivity to H-2 or a syngas with H-2/CO molar ratio at the La loading of 3.0 wt%.