Nickel phyllosilicate derived Ni/SiO2 catalysts for CO2 methanation: Identifying effect of silanol group concentration

Abstract

For the conventional Ni/SiO2 catalyst, the weak metal-support interaction usually resulted in serious Ni sintering at high temperature. To address this problem, a group of Ni-phyllosilicate-derived Ni/SiO2 catalysts were synthesized via the hydrothermal reaction of nickel nitrate and mesostructured silica nanoparticles (MSN) with three different sizes of 99 (MS), 184 (MM), and 725 (ML) nm. The Ni contents of three nickel phyllosilicate catalysts varied from 5.9 to 19.7 wt%, which exhibited a reverse order of the particle size. It was found that the concentration of silanol group (SiOH) of MSN significantly affected the construction of Ni-phyllosilicate material. The surface silanol group concentration increased with the decrease of particle size of MSN, resulting in the improved formation of nickel phyllosilicate and enhanced catalytic activity for CO2 methanation. Among all catalysts, MS/H-24 showed the highest CO2 conversion of 76.5 % at 450 °C due to the highest Ni dispersion and largest CO2 and H2 uptakes. In addition, the optimal catalyst exhibited higher anti-sintering property, long-term stability and hydrothermal stability than an impregnated catalyst (Ms/Im) with the similar Ni content in a lifetime test (450 °C, 100 h) and steam treatment test (600 °C, 6 h), owing to its strong metal-support interaction derived from nickel phyllosilicate.