Ni/CeO2 catalysts for methane partial oxidation: Synthesis driven structural and catalytic effects

Abstract

Catalytic partial oxidation of methane (CPO) to synthesis gas was performed over differently prepared CeO2 supported nickel catalysts with 6wt% Ni content. The samples were synthesized by microwave assisted procedures and by hydrothermal deposition procedure. Differences in the catalyst structural properties of the prepared catalysts were detected by XRD, TPR and XPS measurement. When tested at atmospheric pressure with feed gas mixture containing methane and oxygen in molecular ratio CH4/O2=2, all the samples reached 98% conversion with CO selectivity values >95% in the 700–800°C temperature range. The samples exhibited different behavior towards carbon formation during the tests. Moreover, according to XRD, XPS and TGA results, when the carbon was formed it did not cause catalyst deactivation. TPR profiles confirmed different degree of chemical interaction between NiO and CeO2 support, depending on the preparation method. The building up or the easy removal of carbon during the CH4 temperature programmed surface reaction (TPSR), substantiate the role of the CeO2 lattice oxygen mobility, enhanced by metal-support interaction, in the removal of the deposited carbon through CO evolution. Structure-activity relationship established a close dependence of the CPO performance on the combination of NiO and CeO2 crystallite sizes and the interaction between the two.