Highly active and stable Ni-incorporated spherical silica catalysts for CO2methanation

Abstract

Nickel-doped spherical silica (SSP) catalysts with ca. 10 wt% Ni were prepared via a sol-gel method using cetyltrimethyl ammonium bromide as the structure directing agent with different loading sequences of Ni and Si sources (Si1_Ni2, Ni1_Si2, and Ni_Alt_Si). For comparison purposes, the SSP supported Ni catalysts were also prepared by impregnation method (Ni/SSP (Imp)). All the prepared catalysts showed spherical shape with high specific surface area (357-868 m2/g). The X-ray diffraction and H2-temperature programmed reduction results revealed the stronger interaction between Ni and SiO2 in the form of nickel silicate for all the Ni-doped SSP catalysts except Ni/SSP (imp), in which only NiO species were detected. For the reaction temperature 350 ̊C, the CO2 conversion was in the order: Ni_Alt_Si (51%) > Ni1_Si2 (49%) > Si1_Ni2 (28%) > Ni/SSP (Imp) (10%) with methane selectivity 80–95%. The superior performances of the Ni_Alt_Si catalyst were correlated well to the higher electron density of Ni on the surface and higher CO2 adsorption ability as revealed by the X-ray photoelectron spectroscopy and CO2-temperature program desorption results.