Efficient integration of CO2 capture and conversion over a Ni supported CeO2-modified CaO microsphere at moderate temperature

Abstract

Efficient integration of calcium-looping (CaL) and dry reforming of methane (DRM), termed as CaLDRM, into an isothermal process implemented on a bifunctional Ni-CaO based material is a promising technology to achieve CO2 capture and in-situ conversion to syngas, thereby allowing a win–win for environment and economy. The core of this technology is the employed material which should ensure both good CO2 capture capacity and significant catalytic activity at a temperature matching CaL and DRM. To this end, we synthesize a Ni supported porous CeO2-modified CaO microsphere to serve as the bifunctional material by a combination of template-assisted hydrothermal and impregnation method. This material successfully drives cyclic CO2 capture and conversion at the same temperature of 650 °C, i.e. simultaneously realizing high-temperature CaL and low-temperature DRM. The role of Ce on boosting the material performance originates from two aspects: on the one hand, the homogeneously mixed CeO2, as an activity promoter, enhances the CO2 affinity of CaO and the low-temperature activity of Ni, enabling higher CO2 capture and conversion capacities at 650 °C; on the other hand, it, as a structure stabilizer, improves the sinter resistance of CaO and the dispersion of Ni, maintaining the CaL kinetics and catalytic DRM activity. Following the premise of minimizing additive quantity, the bifunctional material constructed from the support with a Ca:Ce molar ratio of 85:15 shows stable CO2 uptake and syngas yield during the isothermal CaLDRM cycles at 650 °C, exceeding the performance of unmodified material by more than 2 times.