A superior strategy for CO2 methanation under atmospheric pressure: Organic acid-assisted Co nanoparticles assembly on diatomite

There is an urgent need to find a cost-effective and energy-efficient catalysts to promote industrial CO2 methanation, and organic acid-assisted Co/diatomite catalysts stands out as a promising alternative strategy. Herein, nine different kinds of organic acid were introduced to assist the assembly of Co nanoparticles on surface of the diatomite (Dt). Among these catalysts, the superior catalytic performance on citric acid (CA)–Co/Dt was attributed to the fact that CA has more hydroxyl and carboxyl groups. The amount of citric acid addition was adjusted to reach the optimal CA/Co molar ratio and consequently the best catalytic performance. 0.5CA-Co/Dt catalyst showed excellent catalytic activity for CO2 methanation with 73% CO2 conversion and 96% CH4 selectivity at 400 °C (GHSV = 20000 mL gcat−1 h−1, P = 1 atm), and exhibited good stability in long-term reaction. The addition of citric acid changed the surface properties, such as the morphology of Co3O4, cobalt oxidation state, basic sites and defect sites, which affected the catalytic performance. The mechanism analysis showed that the improved catalytic performance was attributed to the refinement and increased dispersion of Co nanoparticles, which increased the active catalytic sites on the catalyst surface, enhanced metal-support interaction, and improved the anti-sintering properties. The outstanding features of CA-assisted Co/Dt provide another promising strategy for the design of high-performance CO2 methanation catalysts.