Influence of the ultrasound power density in the ultrasound-assisted synthesis of Ni-based LDH catalysts for CO2 methanation

Abstract

Ultrasound-assisted co-precipitation method was used to synthesize Ni-LDH based catalysts for CO2 methanation. The influence of ultrasonic irradiation power density (90, 180, 270, and 360 W·L−1) on the physico-chemical properties of the catalysts as well as on their catalytic behavior was studied as compared to catalysts prepared by conventional co-precipitation. Based on the XRD results, ultrasound decreases the crystallite size of LDH structure whatever the power density used as compared to the conventional method, and by increasing the ultrasound power density, the crystallite size increases. This effect on dried samples leads to an increase in the size of nickel particles on the catalysts. 90 W·L−1 improves Ni particle distribution, catalyst basicity, and reducibility. Finally, Ni Us 90, the most performant catalyst in the studied series, shows a CO2 conversion of 80 % and a CH4 selectivity of 99.9 % at 350 ℃ with no deactivation for 100 hours under reaction conditions.