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

The Mn doping nanocrystalline Co–Ce–Zr–Ox 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), O2 temperature-programmed desorption (O2-TPD), X-ray photoelectron spectroscopy (XPS) and temperature-programmed hydrogenation (TPH). Their catalytic performances for methane reforming with CO2 to hydrogen and carbon monoxide were investigated. Adding Mn remarkably enhanced the catalytic activity and stability of the Co–Ce–Zr–Ox 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–Ox 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–Ox samples. TPH characterization showed that the surface coke species could be easily oxidized into COx 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 CoOx crystallites. In comparison with the impregnated samples, CoOx species dispersed better in the co-precipitated catalysts.