CO2 methanation and co-methanation of CO and CO2 over Mn-promoted Ni/Al2O3 catalysts

A series of Mn-promoted 15 wt-% Ni/Al2O3 catalysts were prepared by an incipient wetness impregnation method. The effect of the Mn content on the activity of the Ni/Al2O3 catalysts for CO2 methanation and the co-methanation of CO and CO2 in a fixed-bed reactor was investigated. The catalysts were characterized by N-2 physisorption, hydrogen temperature-programmed reduction and desorption, carbon dioxide temperature-programmed desorption, X-ray diffraction and high-resolution transmission electron microscopy. The presence of Mn increased the number of CO2 adsorption sites and inhibited Ni particle agglomeration due to improved Ni dispersion and weakened interactions between the nickel species and the support. The Mn-promoted 15 wt-% Ni/Al2O3 catalysts had improved CO2 methanation activity especially at low temperatures (250 to 400 degrees C). The Mn content was varied from 0.86% to 2.54% and the best CO2 conversion was achieved with the 1.71Mn-Ni/Al2O3 catalyst. The co-methanation tests on the 1.71Mn-Ni/Al2O3 catalyst indicated that adding Mn markedly enhanced the CO2 methanation activity especially at low temperatures but it had little influence on the CO methanation performance. CO2 methanation was more sensitive to the reaction temperature and the space velocity than the CO methanation in the co-methanation process.