Methanation of Metal Carbonates with Mechano-Energy Using H2O as a Reducing Agent

In the CCS process, substantial quantities of CO 2 emitted by industries such as thermal power stations are captured and converted into carbonate. Consequently, the CO 2 is stored underground in its original form. In this study, we demonstrate the complete conversion of CaCO 3 to CH 4 under mild mechanochemical conditions, using a nickel catalyst in the presence of aluminum. Development of methanation processes from metal carbonates is important for carbon-neutral energy systems, however, the high chemical stability of carbonates limits direct conversion to methane. Here, we report a mechanochemical approach for methane production from metal carbonates. Using a commercially available Ni/Al alloy and H₂O, methane formation from relatively unreactive carbonates proceeded without external heating or hydrogen pressurization. Under the conditions, high yields of methane (up to >99%) were obtained for several carbonates, especially in calcium carbonate, manganese carbonate hydrate, and copper carbonate, copper hydroxide complex. X-ray photoelectron spectroscopy (XPS) analysis of the Ni/Al powder at different reaction stages suggests a reversible change in the nickel oxidation state [Ni (0) → Ni (Ⅱ) → Ni (0)] during the process. The present method enables methane production under mild conditions and shows potential for improved energy efficiency compared with previously reported approaches.