Thermal stability and surface structure of Mo/CeO2 and Ce-doped Mo/Al2O3 catalysts

In order to explore the influence of CeO 2 on the structure and surface characteristics of molybdena, an investigation was undertaken by using N 2 adsorption (BET method), thermal analysis and in-situ diffuse reflectance infrared (DRIFT) techniques. In this work, the Mo/CeO 2 and Ce-Mo/Al 2 O 3 samples were prepared by impregnation and co-precipitation methods with high Mo loadings. Combining the results one may notice that the presence of ceria led to the increase of polymerized surface Mo species so as to forming Mo-O-Ce linkages besides the formation of coupled O=Mo=O bonds indicative of polymeric MoO 3 . From thermal analysis, it can be inferred that Mo/Al 2 O 3 is the thermally most stable material in the temperature range used in the experiment (up to 900°C), whereas Ce-Mo/Al 2 O 3 and Mo/CeO 2 samples undergo morphological modifications above 700°C resulting in lattice defects, which motivate the mobility of Mo and Ce ions and thus enhance the possibility of interaction between them. Additionally, their activity towards CO adsorption needs reduced ceria and molybdena containing coordinatively unsaturated sites (CUS), oxygen vacancies and hydroxyl groups to form various carbonate species.