Effect of Cerium Promoters on an MCM-41-Supported Nickel Catalyst in Dry Reforming of Methane

0.1-3 wt % Ce-promoted MCM-41-supported nickel catalysts were prepared for dry reforming of CH4(DRM) and characterized by surface area and pore analyses, powder X-ray diffraction , temperature-programed reduction with H-2 temperature-programed CO2 desorption, X-ray photoelectron spectroscopy, thermogravimetric analysis, and scanning transmission electron microscopy using a high-angle annular dark field. Notably, 5Ni0.5Ce/MCM-41 has a bimodal distribution of NiO crystallites inside and outside the pores of MCM-41, the highest number of basic sites inducing profound CO2 interactions with the surface, and metallic nickel particles interacting with the support for facilitating CH4 dissociation. In addition, a thin surface layer of ceria provides surface oxygen species for carbon deposit oxidation. All these physiochemical properties ensured >90% conversion (H-2/CO similar to 1) over 330 min on stream and >80% conversion over 75 h of time on stream (H-2/CO = 0.98) over the 5Ni0.5Ce/MCM-41 catalyst. A higher ceria loading than 0.5 wt % masked the active Ni sites with a ceria layer, which diminished the number of basic sites and deteriorated the catalytic performance.