Synthesis Characterization and Activity Pattern of Ni-Al Hydrotalcite Catalysts in CO2 Methanation

Two nickel-aluminum hydrotalcite samples (HTLCs) were prepared by a coprecipitation method at different pH values and investigated as catalysts for the hydrogenation of carbon dioxide. The newly synthesized samples have been compared with a reference alumina supported nickel-based commercial catalyst, with equal nickel content. The as-prepared and commercial samples were characterized by BET analysis, atomic adsorption spectroscopy (AAS), X-ray diffraction (XRD), and temperature-programmed techniques (H2-TPR and CO-TPD). Catalytic activity of the analyzed samples was investigated toward hydrogenation of CO2 at atmospheric pressure by varying reaction temperature between 250 and 400 °C. The maximum CO2-to-CH4 conversion value achieved by hydrotalcyte was 86% at 300 °C. The superior performance of HTLCs has been put in relationship with the major catalysts reducibility nature and with the higher metal surface area and metal dispersion. The stability of the HTLCs was investigated through long-term tests, resulting in good stability in the reported reaction conditions.