Two birds with one stone: MgO promoted Ni-CaO as stable and coke-resistant bifunctional materials for integrated CO2 capture and conversion

Abstract

Calcium Looping coupling with CH4 dry reforming (CaLDRM) is a promising technology to achieve CO2 capture and in-situ conversion to syngas, thereby attracting much attention recently. However, the significant coke deposition and reduced activity of the Ni-CaO based bifunctional materials hinder its practical application. In this work, low-cost MgO was utilized to promote Ni-CaO bifunctional material, which successfully drives cyclic CO2 capture and conversion. On the one hand, MgO act as a stabilizer to inhibit CaO sintering, acquiring excellent CO2 capture ability and cycle stability. After 20 cycles, the 10 wt% MgO promoted Ni-CaO bifunctional materials (Ni-Ca10Mg) maintained the CO2 capture capacity of 0.53 gCO2/gmaterial, much higher than the unmodified material. On the other hand, MgO can form NiO-MgO solid solution with NiO, bringing fine Ni particle sizes and abundant oxygen species. Thanks to the effect of NiO-MgO solid solution, Ni-Ca10Mg demonstrated stable CO2 conversion and syngas yield during the isothermal CaLDRM cycles, while the coke depositions are only 0.0395 gcoke/gmaterial after 10 CaLDRM cycles, corresponding to 37.2 % of unmodified material.