Catalytic performance and regenerability of Ni/CeZrSmOx catalysts for dry reforming of methane

Abstract

The effect of zirconium and samarium as promoters and dopants of Ni/CeO₂ catalysts for dry reforming of methane (DRM) has been investigated. The catalysts were prepared by coprecipitation within inverse microemulsions, which allow achieving good structural homogeneity and surface area. They were characterized using nitrogen adsorption-desorption isotherms, X-ray diffraction (XRD), temperature programmed reduction (TPR), temperature programmed oxidation (TPO), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The catalysts, preactivated in a flow of 10 % O₂/He and further under the reactant stream, have been tested in DRM, using samples both fresh and upon regeneration after their first use at 700 ºC for 5 h at atmospheric pressure. The effect of spatial velocity has been also investigated. Different catalytic properties are revealed as a function of the nature of the support in each case. While the undoped Ni-Ce catalyst exhibits high DRM activity, its deactivation is shown to depend on the spatial velocity applied, and a relatively high stability is observed at high contact time. While all systems suffer deactivation caused by the formation of carbon deposits as well as sintering of the nickel and support, the presence of zirconium is shown to provide a higher stability to the systems as a consequence of enhanced redox properties and lower nickel size, which can limit deactivation by carbon deposits. In contrast, a relatively higher deactivation due to carbon deposits is observed upon doping with samarium.