CO_2 methanation over Co-Ni bimetal-doped ordered mesoporous Al_2O_3 catalysts with enhanced low-temperature activities

摘要

The Ni based catalysts have been considered as potential candidates for the CO2 methanation owing to the low cost. However, the poor low-temperature catalytic activities limit their large-scale industrial application. In order to address this challenge, a series of Co-Ni bimetal doped ordered mesoporous Al2O3 materials have been designed and fabricated via the one-pot evaporation induced self-assembly strategy and employed as the catalysts for CO2 methanation. It is found that the large specific surface areas (up to 260.0 m(2/)g), big pore volumes (up to 0.59 cm(3)/g), and narrow pore size distributions of these catalysts have been successfully retained after 700 degrees C calcination. The Co and Ni species are homogenously distributed among the Al2O3 matrix due to the unique advantage of the one-pot synthesis strategy. The strong interaction between metal and mesoporous framework have been formed and the severely thermal sintering of the metallic Co-Ni active centers can be successfully inhibited during the processes of catalyst reduction and 50 h CO2 methanation reaction. More importantly, the synergistic effect between Co and Ni can greatly enhance the low-temperature catalytic activity by coordinating the activation of H-2 and CO2, prominently decreasing the activation energy toward CO2 methanation. As a result, their low-temperature activities are evidently promoted. Furthermore, the effect of the Co/(Co + Ni) molar percentage ratio on the catalytic property has been also systematically investigated over these catalysts. It is found that only the catalyst with appropriate ratio (20.0%) behaves the optimum catalytic performances. Therefore, the current Co-Ni based ordered mesoporous materials promise potential catalysts for CO2 methanation. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.