Model MO-V-TE-O catalysts for propane oxidation to acrylic acid: New fundamental insights from studies of surface active sites

Multicomponent bulk Mo-V-M oxides (M = a mixture of Nb, Te, Sb, etc.) containing complex mixtures of so-called "orthorhombic" (M1) and "hexagonal" (M2) phases were studied due to their promise as new highly active and selective catalysts for propane oxidation to acrylic acid. A series of model Mo-V-Te-O catalysts was synthesized and characterized by XRD, SEM, TEM, XPS, kinetic studies of propane oxidation as well as low-energy ion scattering (LEIS). The bulk characterization techniques (XRD, TEM, SEM) indicated that the model catalysts contained pure M1 and M2 phases as well as their mixtures. Further insights into the compositional depth profile of these catalysts came from combined ICP (bulk), XPS (surface region), and LEIS (topmost surface layer) studies. The results of the LEIS studies in particular, in combination with the results of kinetic studies, provided new critical insights into the functions of the various surface species in the selective oxidation of propane over model Mo-V-Mo oxide catalysts. This is an abstract of a paper presented at the 227th ACS National Meeting (Anaheim, CA 3/28/2004-4/1/2004).