A series of CeO2-ZrO2 composite oxides (Ce1-xZrxO2) was characterized and tested for the gas-solid reaction with CH4 in the absence of gaseous oxidant. A solid solution with fluorite structure was formed for the samples with Zr content below 50% (x less than or equal to 0.5). For Ce1-xZrxO2 both desorption of O-2 and reduction by H-2 took place at lower temperatures as compared with that for CeO2 alone. Like CeO2, the reaction of Ce1-xZrxO2 with CH4 selectively produced synthesis gas with a H-2/CO ratio of 2, but the formation rates of H2 and CO were increased and the activation energy was remarkably decreased due to the incorporation of ZrO2 into CeO2. The reaction was further accelerated by the presence of Pt catalyst. The conversion of CH4 to HZ and CO could be achieved at a temperature as low as 500 degrees C by using Ce0.8Zr0.2O2 in the presence of Pt. The reduced Ce0.8Zr0.2O2-y could be oxidized with H2O back to Ce0.8Zr0.2O2, producing pure H-2 simultaneously. (C) 1999 Elsevier Science B.V. All rights reserved.