Manganese promoting effects on the Co–Ce–Zr–O x nano catalysts for methane dry reforming with carbon dioxide to hydrogen and carbon monoxide

Abstract

The Mn doping nanocrystalline Co–Ce–Zr–O x catalysts were prepared by the co-precipitation method and characterized by various physico-chemical characterization techniques such as X-ray diffraction (XRD), temperature- programmed reduction (TPR), O 2 temperature-programmed desorption (O 2-TPD), X-ray photoelectron spectroscopy (XPS) and temperature-programmed hydrogenation (TPH). Their catalytic performances for methane reforming with CO 2 to hydrogen and carbon monoxide were investigated. Adding Mn remarkably enhanced the catalytic activity and stability of the Co–Ce–Zr–O x catalyst. The highest catalytic activity and long-term stability was obtained when the molar ratio of Mn/(Ce + Zr + Mn) was 10%. The improved catalytic behavior was closely related to the surface oxygen species and oxygen mobility. In comparison with that of Co–Ce–Zr–O x catalyst, the migration of bulk lattice oxygen species became easier, and the content of surface oxygen species was higher for the Mn-doped nanocrystalline Co–Ce–Zr–O x samples. TPH characterization showed that the surface coke species could be easily oxidized into CO x for the Mn-doped nano cobalt-composite catalyst due to the higher amount of mobile oxygen. The Mn incorporation promoted the dispersion of the nano-sized CoO x crystallites. In comparison with the impregnated samples, CoO x species dispersed better in the co-precipitated catalysts.