Syngas production from partial oxidation of methane over Ce1-XNiXOY catalysts prepared by complexation-combustion method

Synthesis gas production from partial oxidation of methane (CH4/O-2/Ar = 4/2/94) over Ce1-xNixOY (X = 0.05-0.6) catalysts was investigated between 500 and 900 degrees C by using a jet stirred reactor. The highest conversion rate of CH4 and O-2 was obtained on Ce0.6Ni0.4OY where the selectivity of hydrogen was close to 80% and the CO selectivity was higher than 90%, although the residence time was very low (delta = 3 s). The desired ratio H-2/CO about 2 was obtained at about 700 degrees C for all catalysts. Moreover, the catalyst exhibited good stability as no reaction activity decrease was observed during 160 h reaction at 650 degrees C due to the high redox property of the catalyst in the reaction. The structure and property of the catalysts were investigated by XRD, TPR, BET, N-2-adsorption, and XPS for the fresh and used samples. The TPR and XPS results suggested that Ce3+/Ce4+ and Ni2+/Ni-o couples coexisted in the reaction by Ni2+ + Ce3+ + square --> Ni-0 + Ce4+ due to the strong interaction between the Ni and Ce species in the catalysts. The lattice oxygen actived by Ce3+ with oxygen vacancy is the main active oxygen species for the reaction. Both Ni-0 and Ce3+ with oxygen vacancy are the active sites for the reaction. The active site transferred between Ni-0 and Ce3+-square depending on the availability of lattice oxygen in the reaction. (C) 2006 Elsevier B.V. All rights reserved.