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

Abstract

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.