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Selective methanation of carbonate@carbon composite formed by the reaction of carbon dioxide with alkali metals

We systematically studied the thermochemical behaviors of alkali metals under the carbon dioxide (CO2) atmosphere and first investigated the hydromethanation performance of the alkali metal carbonate@carbon product formed in the reaction of CO2 with alkali metals. The on‐set reaction temperature of alkali metals with CO2 is at about 466, 584, and 595°C, respectively, following Li < Na < K. The experimental results indicate that COx‐free methane can be selectively and efficiently generated by hydrogenation of these carbonate@carbon composites at 450°C without a catalyst. Among these carbonate@carbon composites, the Li2CO3@carbon composite shows superior methanation performance. The selectivity of methanation is near 100%. The yield and content of methane are able to reach 30.3% and 26.6 mol%, respectively. This work provides an alternative method to produce methane, utilizing CO2 resources.