Highly Efficient Ni-Phyllosilicate Catalyst with Surface and Interface Confinement for CO2 and CO Methanation

For the conventional Ni/SiO2 catalyst, it is a challenge to address the sintering problem of Ni particles, especially at high Ni loading. A series of Ni-phyllosilicate catalysts were prepared through the hydrothermal reaction of mesoporous SiO2 nanorods (SRs) and nickel nitrate, followed by an impregnation modification of CeO2. Hydrothermal temperature played an important role in the formation of nickel phyllosilicate. A small amount of Ni-phyllosilicate with a Ni content of 18.56 or 23.88 wt % was formed at a low hydrothermal temperature of 120 or 160 degrees C, and a large amount of nanosheet-like Ni-phyllosilicate with the Ni content as high as 31.65 wt % was obtained at a high hydrothermal temperature of 200 degrees C. The prepared Niphyllosilicate catalysts were beneficial to obtain Ni particles with small sizes (3.3-6.3 nm), even though they were reduced at 750 degrees C and possessed high Ni loadings (18.56-31.65 wt %) owing to the surface and interface confinement of nickel phyllosilicate. After the modification of CeO2 using an impregnation method, the CeO2 promoter could further reduce the Ni particle size and increase hydrogen and carbon dioxide uptakes. The CeO2-modified Niphyllosilicate catalyst (NPS-180-5C) was the best catalyst in this work, which could reach the thermodynamic equilibrium of CO methanation above 350 degrees C and exhibited high catalytic activity for CO2 methanation. In addition, for the 55 degrees C-100 h-lifetime test for CO2 methanation and 600 degrees C-6h-100% steam treatment tests, NPS-180-5C also showed an excellent antisintering property and higher hydrothermal stability than the impregnated one (N/SR-Im) owing to its special structure and confinement effect as well as promotion of CeO2 species. In all, the CeO2-modified SR-derived Ni-phyllosilicate catalyst could not only effectively suppress the problem of easy sintering of metallic Ni particles on the conventional Ni/SiO2 catalysts but also exhibit high catalytic activity and hydrothermal stability, which was a promising catalyst for both CO2 and CO methanation reactions.