Highly stable ceria-zirconia-yttria supported Ni catalysts for syngas production by CO2 reforming of methane

Abstract

Ni/CeO2/YSZ and Ni/Ce0.15Zr0.85O2 have been investigated as catalysts for the dry reforming of methane at 750°C. Ni was incorporated by the impregnation method. The supports were previously activated by using a thermo-chemical protocol consisting on a severe reduction (H2/Ar) at 950°C followed by a mild oxidation (O2/He) at 500°C. According to TPR results, this protocol leads to the development of unique redox properties in the case of the CeO2/YSZ oxide. Two types of CO2+CH4 (1:1) mixtures (helium-diluted and undiluted) were used to feed the reactor. When using the Ni/Ce0.15Zr0.85O2 catalyst with undiluted feed, the reactor became plugged by coke. By contrast, Ni/CeO2/YSZ behaved as an active and stable catalyst even under the most severe operation conditions. The characterization of the spent Ni/CeO2/YSZ using TGA, TEM, Raman and XPS spectroscopy revealed that only a limited amount of graphitic carbon, in form of nanotubes, was formed. No evidences of deactivating carbonaceous forms were obtained. The singular redox properties of the activated CeO2/YSZ oxides are proposed as a key for designing Ni catalysts highly stable in reforming processes.