Ni catalysts with La as promoter supported over Y- and BETA- zeolites for CO2 methanation

Abstract

The hydrogenation of CO2 into methane is considered a plausible process to storage renewable energy in form of methane and reducing CO2 anthropogenic emissions. Microporous solids such as zeolites have been scarcely studied yet for this application. This study aims to evaluate and compare the catalytic performance of zeolite (Y and BETA) supported Ni catalysts for CO2 methanation. The physicochemical properties of the prepared catalysts were characterized by XRD, BET, CO2-TPD, H2-TPR and XPS, and CO2 methanation was carried out in a tubular reactor at conditions of H2/CO2 = 4, GHSV = 10,000 h−1 and temperatures from 200 to 500 ⁰C. Neutralization of both zeolites by Na+ ion exchange enhanced the CO2 conversion as weaker CO2 adsorption sites and reducibility are promoted. BETA resulted in a better support than Y zeolite due to the presence of more easily reducible Ni2+, which acts as precursor of active Ni° accessible under reaction conditions. Indeed, the surface basicity and Ni dispersion of Ni/BETA catalysts were considerably promoted by impregnation of different loads of La2O3, which increase the amount of CO2 adsorption sites and even active hydrogenation sites resulting in a significant increase of activity and selectivity towards CH4. The optimal Ni-10%La2O3/Na-BETA formulation resulted in T50 of 320°C, CO2 conversion of 65% at 350 °C, with almost total selectivity to CH4 and maintaining stability for more than 24 h.