Carbon Dioxide Reforming of Methane to Synthesis Gas Over Supported Ni Catalysts Prepared From Ni-M (M: Mg and Ca)/Al-Layered Double Hydroxides

In this work, Ni-catalysts for carbon dioxide reforming of methane were prepared by solid phase crystallization (spc) method. We investigated two catalysts: spc-Ni-M/Al with M being Mg or Ca. The catalysts were tested for CO2 reforming of methane. The activities of the catalysts, such as CH4 conversion, H2 and CO yield, and H2/CO ratio, were studied in relation to the composition of the catalysts. The effect of the reduction period with H2 and the effect of CH4/CO2 ratio were investigated for both catalysts. Compared with Ni-Mg/Al catalyst, the Ni-Ca/Al catalyst showed higher conversion of methane over a 20 hrs period for CH4/CO2 ratios lower or equal to one. However, when the CH4/CO2 feed ratio is greater than one, the Ni-Ca/Al shows rapid deactivation, which was not observed for the Ni-Mg/Al catalyst. In addition, CO2 reforming over the Ni-Ca/Al catalyst was able to produce synthesis gas (H2 and CO) without pre-reducing the catalyst (up to 65% conversion at 700„aC), whereas without pre-treatment the Ni-Mg/Al catalyst yielded conversion between 0 and 5%. The Ni-Ca/Al catalyst was more easily reduced to form active Ni metal particles due to the weak interaction strength between Ni and Ca; this phenomenon was confirmed with temperature-programmed reduction analysis (TPR). The fresh catalysts and spent catalysts were characterized by XRD analysis; characterization of the carbon deposited on the catalysts' surface was performed with SEM and EDX analysis.