The promoter action of CeO₂ for the Ni/Al₂O₃-catalyzed methanation of CO₂

Abstract

By adding 2 wt % CeO₂ to the active metal (Ni) or to the Al₂O₃ support, the catalysts for CO₂ methanation were prepared and the effect of the promoter on the catalytic performance was studied. For the sake of comparison, the 15 wt % Ni/Al₂O₃ catalyst was prepared via impregnation method. The CO₂ methanation was carried out in a fixed-bed reactor under atmospheric pressure with a weight hourly space velocity (WHSV) 30000 mL/(g ⁻¹_cat h). It was found that addition of 2 wt % CeO₂ either to the active metal or to the support of the 15 wt % Ni/Al₂O₃ catalyst both increased CO₂ methanation performance. The catalysts were characterized by BET, XRD, H₂-TPR, CO₂-TPD, XPS and TEM techniques. When CeO₂ was added to Ni the interaction of Ni with Al₂O₃ became stronger to decrease the Ni particle size and increase the degree of the Ni dispersion. As a result, the amounts of CO₂ adsorbed on the active sites and the CO₂ conversion considerably increased. When CeO₂ was added into Al₂O₃ to form the composite supports, CO₂ conversion was also increased but the effect was not as high as that observed when CeO₂ was added to Ni.