Three-Dimensional Networked Ni-Phyllosilicate Catalyst for CO2 Methanation: Achieving High Dispersion and Enhanced Stability at High Ni Loadings

It is a great challenge for nickel-based catalysts to obtain high-temperature stable Ni nanoparticles with high dispersion at high loadings. To address this problem, a group of three-dimensional (3D) networked nickel phyllosilicate catalysts were prepared through the hydrothermal reaction of 3D-SBA-15 and soluble nickel salts (Ni(NO3)(2) or Ni(CH3COO)(2)) and were used for the CO2 methanation reaction to produce CH4 (substitute natural gas). The flower-like nanosheets corresponding to Ni3Si2O5(OH)4 are uniformly generated on the surface of 3D-SBA-15 and become much denser with increasing hydrothermal time, with Ni contents varying in the range of 24.22-30.72 wt %. Upon 750 degrees C reduction of phyllosilicate materials, smallsized Ni particles (<5 nm) can highly disperse and be confined into the silica and unreduced phyllosilicate support due to the strong interaction of the nickel and complex support. In addition, a Ni/3D-SBA-15 catalyst with the high Ni content of 30 wt % was also synthesized for comparison by an incipient wetness impregnation method. For the CO2 methanation reaction, the fabricated phyllosilicate catalyst achieved a higher maximum CH4 yield of 80.4% at 400 degrees C and exhibited a higher long-term stability of 100 h as compared to the impregnated sample. It was noted that the phyllosilicate catalyst also exhibited high hydrothermal stability at 600 degrees C under 100% steam. The enhanced catalytic performance was attributed to the excellent property of nickel phyllosilicate and the special pore structure derived from 3D-SBA-15, which could significantly improve the Ni dispersion and increase CO2 adsorption and H-2 uptake as well as the interaction of nickel-support.