Promotion of active H-assisted CaCO₃ conversion for integrated CO₂ capture and methanation

Carbonate hydrogenation is a new path for the conversion of metal carbonate with potentially lower energy consumption and CO2 emissions comparing to the traditional thermal decomposition, and the integrated CO2 capture and utilization (ICCU) represents its latest development. However, the slow hydrogenation rate of carbonate at low temperatures is one key scientific challenge for applications. Herein, we report an acidity regulation approach to prepare ZrO2-doped Ni/CaO dual-function material with good CO2 capacity, fast and highly selective conversion below 600 degrees C for integrated CO2 capture and utilization by methanation (ICCU-methanation). Experiments and DFT calculations show that the introduction of ZrO2 as acid sites effectively strengthens *H adsorption and reduces the formation barrier of intermediate *COOH during carbonate hydrogenation. Thus, Ni-10(ZrO2)(10)CaO80 exhibits a CH4 STY of 14.1 mmol.min(-1).g(Ni)(-1) at 550 degrees C, 6 times higher than the reference DFM. Furthermore, the presence of O-2 in flue gas is observed to have no effect on ICCU-methanation, but steam could delay the in-situ methanation. Long-term cyclic test shows that the optimal Ni-10(ZrO2)(5)CaO85 has a stable CO2 capacity of 7.5 mmol.g(DFM)(-1), 98 % CO2 conversion and 95.5 % CH4 selectivity under flue gas containing both steam and O-2 at 600 degrees C, suggesting a good potential to be applied in ICCU-methanation.