Methane partial oxidation over Ni/CeO2-ZrO2 mixed oxide solid solution catalysts

In this study, methane partial oxidation (MPO) to synthesis gas over Ni/Ce1-xZrxO2 (x = 0, 0.25, and 1.0 with varying Ni loading of 5, 10 and 15 wt.%) was investigated over the temperature range of 400-800degreesC. The experimental results showed that the catalysts prepared by impregnation method are more active than those prepared by gel impregnation method because of their higher degrees of metal dispersion and reducibility. Under the reaction conditions, MPO over Ni/CeO2 and Ni/Ce0.75Zr0.25O2 mixed oxide catalysts were active at temperatures above 550degreesC whereas that of Ni/ZrO2 took place at temperatures above 650degreesC. The H-2/CO molar ratio of 2.0 +/- 0.05 was obtained. Generally, the CH4 conversion slightly increased while the CO and H-2 selectivities remained unchanged with increasing Ni loading. The Ni/Ce0.75Zr0.25O2 mixed oxide catalysts were found to resist to coke formation more than the other catalysts due to their high degrees of metal dispersion and surface oxygen mobility. The TPO results indicated that a major source of carbon deposition on these catalysts is due to the methane decomposition. Results also showed that the activity and selectivity of the catalysts can be regained after the regeneration under oxidizing atmosphere. (C) 2004 Elsevier B.V. All rights reserved.