Remarkable activity, selectivity and stability of innovative ni catalysts for the CO₂ methanation process

This experimental study reports on the activity of Ni/CeO₂, Ni/M_xO_y-CeO₂ and Ni/La₂O₃-M_xO_y-CeO₂(M= Mg²⁺) during the CO₂ methanation reaction. The characterization of the supports and catalysts were performed using various characterization techniques, i.e., BET, H₂-TPR, XRD, CO₂-TPD and Raman spectroscopy. Sintering and possible coke formation on the catalyst surface were investigated via TEM analysis. The results showed that the modification of CeO₂ with Mg²⁺ favoured the genesis of a separate phase of MgO increasing the moderate basic sites. Furthermore, the incorporation of La³⁺ ions into the crystal structure of CeO2 generated additional surface oxygenvacancy sites. Thus, the concurrently presence of La³⁺ and Mg²⁺ on the catalyst surface helped obtain a catalyst with increased basicity and surface oxygen vacancies, which accelerated the reaction of CO² methanation at low temperature range. In terms of catalytic performance, the experimental results showed that at 350oC, the catalytic activity with regard to CO₂ conversion was: Ni/La-Mg-Ce (50.0%) > Ni/Mg-Ce (43.0%) > Ni/Ce (39.0%) indicating that the catalytic performance depends on the physicochemical properties of the support, as well as, to the effect of the promoter (La³⁺ and Mg²⁺) on the CeO² support. Finally, the Ni/La-Mg-Ce catalyst showed the highest catalytic activity in terms of the conversion of CO² (50.0%), CH₄ yield (50.0%) and the selectivity of CH4 (100%) at low temperature range.