Highly selective room-temperature catalyst-free reduction of alkaline carbonates to methane by metal hydrides

The realization of effective CO2 conversion into valuable hydrocarbons is a promising way of addressing the current environmental and energy issues. A convenient, highly selective, and efficient method of CO2 methanation and the synthesis of COx-free hydrogen/methane fuel mixtures by ball milling-induced reactions of alkaline carbonates with metal hydrides (MHs) is reported. The natural resources of MgCO3/CaCO3 and MgH2/CaH2 are used as carbon and hydrogen sources, respectively. Mechanochemical investigations of the room-temperature reactions indicate that some alkaline carbonates can be reduced by MHs under catalyst-free conditions to selectively afford CH4 as the sole hydrocarbon product in yields of up to 73%. Moreover, the contents of methane in the gaseous products and its yield are shown, which mainly depend on the nature of metal carbonates/hydrides, rate and duration of ball milling, and reaction mixture composition. Thus, this study opens new ways to achieve the CO2 utilization and synthesize of COx-free hydrogen and methane fuel mixtures.