Bifunctional Ni-Ca based material for integrated CO2 capture and conversion via calcium-looping dry reforming

Abstract

Effective integration of CO2 capture and its conversion is an attractive strategy to reduce the anthropogenic CO2 emissions meanwhile achieve the potential revenue of CO2 molecule. Calcium-looping dry reforming of methane (CaLDRM) has emerged as such a promising process, implemented over a bifunctional reactor combining a CaO-based sorbent and a Ni-based catalyst, to achieve CO2 capture and in-situ conversion with CH4 into syngas. Herein, we synthesize a bifunctional Ni-Ca based material, i.e. Ni and CeO2 nanoparticles co-loaded on ZrO2-coated CaCO3, which enables isothermal capture and release of CO2 at the temperature favorable for DRM reaction, allowing to operate CaLDRM process in a single reactor by simple gas switching. Thanks to the stabilization effect of the ZrO2 layer, both CaO and Ni particles are exempted from severe sintering, maintaining the activity of capture and catalysis. The addition of CeO2 contributes not only to combat the accumulation of inactive carbon during long-term DRM but also to activate CO2 and CH4, accordingly enhancing syngas production, during cyclic CaLDRM. Importantly, the bifunctional material can succesfully drive CaLDRM cycles, converting over 40 % of CH4 and CO2, under 5 vol% CO2 feed concentration (as low as real flue gas) at 720 °C, which is a thermodynamically extremely unfavorable condition (equilibrium conversion below 3 %).