Conversion of carbon dioxide to carbon monoxide: Two-step chemical looping dry reforming using Ca2Fe2O5–Zr0.5Ce0.5O2 composite oxygen carriers

• Published in: Fuel (Guildford) 2022-08, Vol.322, p.124182, Article 124182
• Main Authors: Wang, Luwen, Lin, Yan, Huang, Zhen, Zeng, Kuo, Huang, Hongyu
• Format: Article
• Language: English
• Subjects: Ca2Fe2O5; Calcium zirconate; Carbon dioxide; Carbon monoxide; Chemical looping dry reforming (CLDR); CO2 splitting; Oxidation; Oxygen; Oxygen carrier; Reactivity; Redox reactions; Reduction; Reforming; Sintering; Transmission electron microscopy; X-ray diffraction; Zr0.5Ce0.5O2
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2022.124182

•A two-step chemical looping dry reforming (CLDR) using Ca2Fe2O5(CF)- Zr0.5Ce0.5O2(ZC) was studied.•CF6(60 wt% CF + 40 wt% Zr0.5Ce0.5O2) has the most CO yield during CO2 oxidation.•The suitable reaction temperature of CF6 OC is determined at 850℃.•Cyclic performance of CF6 decreases in the first 5 cycles and then tends to be stable in the following 15 cycles.•Although the cyclic performance decreases, the CO yield of CF6 is still more than that of CF OC. In this study, Zr0.5Ce0.5O2 (ZC) was used to improve the reactivity of Ca2Fe2O5 (CF) oxygen carriers (OCs) and alleviate sintering. The reactivity of modified OCs in Chemical looping dry reforming (CLDR) was explored using a thermogravimetric analyzer and a fixed-bed reactor, and the fresh and reacted OCs were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results revealed that CF6 (60 wt% CF + 40 wt% ZC) had the best reactivity. Owing to the addition of ZC, the carbon monoxide (CO) yield of CF6 was twice that of CF during carbon dioxide (CO2) oxidation, increasing from 72.3 mL/g to 138 mL/g. In the cyclic experiments, the CO yield from CO2 oxidation decreased from 138 mL/g in the first cycle to 34.3 mL/g in the fifth cycle and subsequently stabilized over the next 15 cycles. The decrease in cyclic performance is related to the sintering of the sample and the formation of a new phase, CaZrO3, which hindered the redox reaction in the sample. Although CF6 had a decreased cyclic performance, it still had a better reactivity than CF, which had a CO yield that was about 20% lower than that of CF6. The reason for the improvement is that ZC improved the dispersibility of CF. After 20 cycles, the generation of CO was facilitated by extending the reduction time of the OC, and the CO yield increased from 35 mL/g to 60 mL/g when the reduction time was doubled.