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Some factors such as catalyst, temperature, space velocity, feed CO2/CH4 ratio, H2O and/or O2 addition, have been examined for stable operation of carbon dioxide reforming of CH4 (CDR) in a fixed-bed reactor under atmospheric pressure. The Ni/Ce-ZrO2/-Al2O3 catalyst showed high activity and stability under all the conditions employed compared with Ni/MgAl2O4. This seems to be due to strong interactions between NiO and support and relatively abundant mobile oxygen species in the Ce-ZrO2 layer: the former would suppress carbon formation step and the latter would activate the carbon elimination step. The carbon deposition over the catalysts in CDR was drastically reduced with a slight increase of feed CO2/CH4 ratio or the addition of H2O in feed. The oxidation of CH4 and/or steam reforming of CH4 occurred simultaneously with carbon dioxide reforming of CH4, where drastic change of a H2/CO ratio was observed, when the feed was composed of CH4, CO2, H2O and/or O2. Keywords: carbon dioxide reforming, synthesis gas, simultaneous reforming, Ni catalysts, Ce-ZrO2