Recent debates over the active site structure of supported vanadia/silica catalysts have suggested the existence of a surface vanadium peroxo-oxo "umbrella" structure. This study definitively demonstrates with Raman and UV-vis spectroscopy that the surface vanadia peroxo-oxo umbrella-like structure is not present for both hydrated and dehydrated supported vanadia catalysts such as supported van...

Nanostructured vanadia model catalysts, i.e. highly dispersed vanadium oxide supported on mesoporous silica SBA-15 (VOx/SBA-15), were prepared. The mechanism for the synthesis of VOx/SBA-15 was elucidated by detailed characterization of the individual synthesis steps using XPS and vibrational spectrocopy. The resulting surface vanadium oxide species (0 – 2.3 V/nm), grafted on the inner pores of...

Formation of vanadia species during the calcination of ball milled mixture of V2O5 with TiO2 was studied by Raman spectroscopy in situ and at ambient conditions. It is found that calcination in air leads to fast (1–3 h) spreading of vanadia over TiO2 followed by a slower process leading to the formation of a monolayer vanadia. The calcinated catalyst showed higher activity during toluene oxidat...

A quantitative method based on UV-vis diffuse reflectance spectroscopy (DRS) was developed that allows determination of the fraction of monomeric and polymeric VO(x) species that are present in vanadate materials. This new quantitative method allows determination of the distribution of monomeric and polymeric surface VO(x) species present in dehydrated supported V(2)O(5)/SiO(2), V(2)O(5)/Al(2)O...

Titania supported vanadium oxide catalysts have been demonstrated to be very efficient catalysts for the selective reduction of NOx with NH3 and have found widespread industrial application for the control of NOx emissions from stationary sources (1). Characterization studies have demonstrated that supported vanadium oxide catalysts consist of a two-dimensional metal oxide overlayer on the oxid...

The interactions between surface sulfate and surface vanadate species present on sulfated supported vanadia catalysts under dehydrated conditions have been investigated with infrared and Raman spectroscopies. The surface sulfate species present on sulfated TiO2, ZrO2, and Al2O3 supports and V2O5/TiO2, V2O5/ZrO2, and V2O5/Al2O3 catalysts have identical molecular structures, i.e., (M-O)3SdO, wher...

The information obtained from the characterization of vanadium oxide single crystal surfaces is related to the study of vanadia nanoparticles supported on silica and alumina thin films, model systems for the so-called ‘‘supported monolayer vanadia catalysts’’. It is found that these particles have properties similar to V2O3 surfaces, where the topmost V ions are involved in vanadyl groups and h...

The oxidative dehydrogenation (ODH) of propane was investigated on vanadia dispersed on alumina containing a nominal polymolybdate monolayer (4.8 Mo/nm2). Dehydrogenation rates and selectivities on these catalysts were compared with those on vanadia domains dispersed on alumina. At a given vanadia surface density, ODH reaction rates per gram of catalyst were about 1.5–2 times greater on MoOx -c...

Vanadia nanoparticles supported on nickel manganese mixed oxides were synthesized by co-precipitation method. The catalytic properties of these materials were investigated for the oxidation of benzyl alcohol using molecular oxygen as oxidant. It was observed that the calcination temperature and the size of particles play an important role in the catalytic process. The catalyst was evaluated for...

Supported vanadium oxide catalysts contain a vanadium oxide phase deposited on a high surface area oxide support (e.g., Al2O3, SiO2, TiO2, etc.) and have found extensive applications as oxidation catalysts in the chemical, petroleum and environmental industries. This review of supported vanadium oxide catalysts focuses on the fundamental aspects of this novel class of catalytic materials (molec...