Coke-promoted Ni/CaO catal-sorbents in the production of cyclic CO and syngas

Compared with conventional CO2 capture and utilization (CCU), the integrated CCU (ICCU) process has attracted attention in reducing total thermal energy and ensuring a simplified process. CO2 capture and the subsequent dry reforming of methane (DRM) during the ICCU employing Ni/CaO catal-sorbents has been proposed for the conversion of waste CO2 with CH4 into syngas. Here, coke-promoted Ni/CaO catal-sorbents were fabricated via CH4 pretreatment, and a highly efficient ICCU process for producing CO and syngas was proposed. High CO2 conversion and high CO production were achieved in the CO2 conversion step employing the reverse Boudouard reaction in tandem with CO2 capture. In the following CH4 conversion step, the spent catal-sorbents were regenerated into syngas via a reaction with CH4, and the carbon sources for the reverse Boudouard reaction were supplied by CH4 decomposition. The C-Ni/CaO catal-sorbent exhibited excellent performances of CO2 capture capacity, and CO and H-2 productivities in consecutive CO2 and CH4 conversions. However, the coke-promoted Ni/CaO catal-sorbents were not completely regenerated in the CH4 conversion step after the 5(th) cycle, which might be due to the sintering of Ni-0/NiO and CaO/CaCO3 materials and the excess amount of coke deposited on the surface of C-Ni/CaO catal-sorbents.