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

Abstract

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 H₂ 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 Ni⁰/NiO and CaO/CaCO₃ materials and the excess amount of coke deposited on the surface of C-Ni/CaO catal-sorbents.