Selective oxidation of methane to syngas using Pr0.7Zr0.3O2–Δ: Stability of oxygen carrier

Abstract

Pr0.7Zr0.3O2–Δ solid solution was prepared by co-precipitation method and used as an oxygen carrier in the selective oxidation of methane to syngas (methane/air redox process). The evolution on the physicochemical properties of Pr0.7Zr0.3O2–Δ during the redox process was studied by means of X-ray diffraction (XRD), H2 temperature-programmed reduction (H2-TPR), O2 temperature-programmed desorption(O2-TPD), Brunauer-Emmett-Teller (BET) surface area measurement and X-ray photoelectron spectroscopy (XPS) technologies. The results indicated that Pr0.7Zr0.3O2–Δ solid solution showed the high activity for the methane conversion to syngas with a high CO selectivity in the range of 83.5%–88.1%. Though Pr–Zr solid solution possessed high thermal stability, lattice oxygen was obviously reduced for the recycled sample due to decreased surface oxygen which promoted oxygen vacancies. The increased oxygen vacancies seemed to enhance the oxygen transfer ability in the redox process and provided sufficient oxygen for the methane selective oxidation, resulting in a satisfactory activity. The problem of hot pot was avoided by comparing fresh, aged and recycle sample in the reaction.