Methane decomposition and self de-coking over gadolinia-doped ceria-supported Ni catalysts

Abstract

Abstract A temperature-programmed methane reaction with self de-coking and a fixed-temperature methane reaction were performed over gadolinia-doped ceria (GDC)-supported Ni catalysts. Experimental results reveal that, at below 810 °C, CO 2 formation rate is higher than that of CO, where below 700 °C, the latter is practically zero. The O species that is needed to form CO and CO 2 during and after CH 4 decomposition are supplied mainly from the bulk lattice of GDC. A drop in the supply rate of the O species from the GDC bulk lattice reduces the rates of CO and CO 2 formation; the CO formation rate decreases much more than the CO 2 formation rate. The CO and CO 2 formation rates can be controlled by both the mobility and the concentration of the bulk lattice oxygen. The concentration of the bulk lattice oxygen influences the self de-coking capability. Low temperature, low concentration of methane gas, or a short methane supply time can result in the formation of only CO 2 during self de-coking.