Effect of reduction degree of Ni-phyllosilicate on the catalytic performance for CO2 methanation: Regulation of catalyst structure and hydroxyl group concentration

Abstract

In order to reveal the interrelationship among reduction degree and catalyst structure as well as surface hydroxyl group concentration of Ni-phyllosilicate, four different reduction temperatures of 550, 600, 700 and 800 °C were used. The results showed that low-temperature reduction could lead to high catalytic activity for CO2 methanation. In detail, the low-temperature partial reduction catalyst treated at 550 °C (Ni/S-550R) obtained the smallest Ni particle size, the highest specific surface area and the largest pore volume, which were beneficial to the chemisorption and activation of H2. In addition, the unreduced nickel phyllosilicate also provided abundant hydroxyl groups to facilitate the activation of CO2. With the increasing of reduction temperature, the reduction degree increased quickly; however, the TEM and XRD results showed that the Ni sintering was serious reduced at 700 or 800 °C. What's more, the SiO2 support also transferred from amorphous to crystalline at high reduction temperature with the significant collapse of pore structure. In all, a series of characterization results displayed that the low-temperature reduction of Ni-phyllosilicate catalyst exhibited strong H2 and CO2 chemisorption and activation capacity compared with the high-temperature-reduction ones leading to high CO2 methanation activity.