CO2 methanation over Ni-Al LDH-derived catalyst with variable Ni/Al ratio

Abstract

CO2 methanation is a promising technology to recycle CO2 into useful chemicals, fuels, and energy, avoiding its emissions in the atmosphere, as well as for the purification of H2 streams containing CO2. In this work, Ni-Al LDH-derived catalysts with Ni/Al ratio between 0.5 and 4 were prepared by co-precipitation and evaluated in CO2 methanation. The samples were characterized by N2 physisorption, X-ray diffraction, temperature-programed reduction, temperature-programmed desorption (CO2-TPD, H2-TPD) and oxidation. Catalytic tests were carried out in a fixed-bed reactor at atmospheric pressure, inlet mixture of H2:CO2:N2 = 4:1:15 and GHSV = 60000 mL (gcat h)−1, in stepwise mode (200–400 °C) and stability at 300 °C. The catalysts presented high activity and selectivity, reaching 92.3 % of CO2 conversion at 300 °C, along with 100 % CH4 selectivity for the catalyst with NiAl = 2 due to its high number of weak-to-medium strength basic sites. The amount of H2-chemisorbed was higher for NiAl = 1, whereas the highest number of basic sites was for NiAl = 2. These results indicate that LDH-derived Ni-Al catalysts with a Ni/Al ratio between 1 and 2 would be suitable for CO2 methanation.