Pulse experiments for testing the dissociation activity of CH4 and CO2 were carried out on supported Ni catalysts (Ni/Al2O3, Ni/La2O3, and Ni/CeO2) with or without pre-adsorbed species on the catalysts. The CO2 pulse on Ni/Al2O3 produced a small amount of CO without pre-adsorbed species, while a CO2 pulse produced more CO in the presence of CH x species on Ni/Al2O3. The CH x species on Ni/Al2O3 promote the dissociation of CO2 on the catalyst. The production of CO by the CH4 pulse was low on Ni/Al2O3 regardless of the presence of adsorbed species by the pre-pulse of CO2, while both H-2 and CO were effectively produced on Ni/CeO2. (C) 2015 Elsevier B.V. All rights reserved.