Yttria Modified ZrO Supported Ni Catalysts for CO Reforming of Methane: The Role of Ce Promoter.

Yttria modified zirconia (YZ) supported on 5 wt % of Ni-based catalysts promoted with ceria (1-3 wt %) were prepared by the impregnation process to investigate their performance for dry reforming of methane. The reforming reactions, conducted at 700 °C and at atmospheric pressure using a CO/CH/N fixed feed ratio of 3/3/1, with a total flow rate of 70 mL/min, revealed that the ceria-promoted catalysts (Ce-Ni-YZ; = 1-3 wt %) enhanced the CH and CO conversions as compared to the reference catalyst (Ni-YZ). A CO conversion of 85% was exhibited by the 3Ce-Ni-YZ catalyst. Despite increased conversions, Ce-Ni-YZ catalysts showed more amounts of carbon deposition as evidenced by the values of TGA, and hence were found to be less stable as compared to the reference Ni-YZ catalyst. The used and fresh catalysts were characterized by BET, H-TPR, XRD, TEM, Raman, TPD, and TGA. TEM images displayed nanoparticle sizes of Ni in the fresh catalysts, while carbon filaments were formed on the spent catalysts. The CO-TPD, H-TPR, and BET results revealed the existence of only weak and moderate basic sites, the increase of total hydrogen consumption, and the surface area values with the addition of the Ce promoter, respectively. The TGA analysis showed that the Ce promoter increased the carbon deposition, while the Raman results indicated the dominance of crystallinity due to the graphitized carbon.