Performance and mechanism study of Ce2(SO4)3 for methane chemical looping partial oxidation

• Published in: Fuel (Guildford) 2023-02, Vol.334, p.126817, Article 126817
• Main Authors: Wang, Chengrui, Fang, Yanhong, Wang, Zhenghao, Long, Mujun, Chen, Dengfu, Duan, Huamei, Li, Yandong, Zhang, Guoquan
• Format: Article
• Language: English
• Subjects: Chemical looping partial oxidation; Density functional theory; Lattice oxygen; Oxygen carrier; Rate-determining step
• ISSN: 0016-2361
• DOI: 10.1016/j.fuel.2022.126817

•Ce2(SO4)3 was chose to chemical looping partial oxidation of methane.•Ce2(SO4)3 had an outstanding syngas selectivity and appropriate molar ratio.•CHx (x = 0–4) tended to adsorb at O site and TS2 was the rate-determining step.•Compared with NiO, Ce2(SO4)3 had a lower lattice oxygen migration energy barrier.•The properties of lattice oxygen were a main cause for their excellent performance. Partially oxidizing methane into syngas via a two-step chemical looping scheme was a promising option for methane transformation. Ce2(SO4)3 was selected to explore the performance and mechanism of methane chemical looping partial oxidation (CLPOM) to syngas. Thermodynamic and kinetic analysis forecast the Ce2(SO4)3 as a promising candidate for CLPOM. Compared with literature, Ce2(SO4)3 not only had an outstanding syngas selectivity, but also an appropriate CH4 conversion and molar ratio, and CH4 conversion could reach 90.5 % of thermodynamic result. As revealed via characterization, Ce2(SO4)3(102) surface had the highest peak intensity and the migration of lattice oxygen played an important role in CLPOM. Some of them were tend to agglomeration and these small particles were less than 5 μm. Density functional theory calculations demonstrated that CH4 series dehydrogenation products tended to adsorb at O site and CH3 → CH2 + H was the rate-determining step. The reaction of surface lattice oxygen atoms and migration of the internal lattice oxygen atoms could inhibit carbon deposition, promote CH4 conversion and syngas generation in experiment. Compared with NiO, Ce2(SO4)3 had a lower energy barrier of lattice oxygen migration, which could increase the reaction rate.