[2A10-2A13] Hydrogen/energy carriers/CCU/carbon recycle (4)

[2A10] Efficient CO₂ conversion to CO by chemical looping over MGa₂O_x (M = Ni, Cu, Co)

○Kang Keke¹, Sota Kakihara¹, Takuma Higo¹, Hiroshi Sampei¹, Koki Saegusa¹, Yasushi Sekine¹ (1. Waseda Univ.)

Keywords:Chemical looping, CO2 conversion, RWGS

Reverse water gas shift (RWGS) can convert CO₂ into CO by using renewable hydrogen. However, this important reaction is endothermic and equilibrium constrained, thus it is traditionally performed at 900 K or higher using solid catalysts. In this work, we found that RWGS can be carried out at low temperatures without equilibrium constraints using a redox method called chemical looping, which uses oxygen and its vacancies on the surface of oxide solids. For this purpose, we developed MGa₂O_x(M=Ni, Cu, Co) materials, by which the reaction can proceed with almost 100% conversion of CO₂ even at temperatures as low as 673 K. This allows the reaction to proceed without equilibrium constraints at low temperatures, and the greatly decreases the cost for the separation of unreacted CO₂ and produced CO. Our new gallium-based material is the first material that can achieve high conversion rates at low temperatures in reverse water gas shift using chemical looping (RWGS-CL). Ni is the best choice for doped-M in this process, and various characterizations such as XRD/XANES/TEM have shown that the redox mechanism of NiGaO_x is a phase change due to the redox of Ga during RWGS-CL processing. This major finding is a big step forward for the effective utilization of CO₂ in the future.