Methane steam reforming over Ni/Ce-ZrO2 catalyst: Influences of Ce-ZrO2 support on reactivity, resistance toward carbon formation, and intrinsic reaction kinetics

Regarding the intrinsic kinetic studies in the present work, the reaction order in methane over Ni/Ce-ZrO2 was observed to be approximately 1.0 in all conditions. The dependence of steam on the rate was non-monotonic, whereas addition of oxygen as an autothermal reforming promoted the rate but reduced CO and H2 production selectivities. The addition of a small amount of hydrogen increased the conversion of methane, however, this positive effect became less pronounced and the methane conversion was eventually inhibited when high hydrogen concentration was added. Ni/Ce-ZrO2 showed significantly stronger negative impact of hydrogen than Ni/Al2O3. The redox mechanism on ceria proposed by Otsuka et al. [K. Otsuka, T. Ushiyama, I. Yamanaka, Chem. Lett. (1993) 1517; K. Otsuka, M. Hatano, A. Morikawa, J. Catal. 79 (1983) 493; K. Otsuka, M. Hatano, A. Morikawa, Inorg. Chim. Acta 109 (1985) 193] can explain this high inhibition.