Effect of the sequence of potassium introduction to V2O5/TiO2 catalysts on their physicochemical properties and catalytic performance in oxidative dehydrogenation of propane

Two series of K-promoted V2O5/TiO2 catalysts were prepared by: (a) deposition of vanadia on K-doped TiO2 support (TiK V preparations), and (b) deposition of K on vanadia-titania catalysts (TiV K preparation). They were characterized by V-51 NMR, XPS, surface potential (work function) techniques and isopropanol decomposition, a probe reaction for the acid-base properties, and tested in oxidative dehydrogenation of propane (ODH), It has been found that the sequence of the K introduction in the preparation step is preserved in the calcined preparations, with more potassium being present on the surface of TN K than TiK V catalysts. The vanadium species on TiK V samples include V2O5 and polymeric [VOx](n) species. The TiV K sequence leads to the formation of potassium vanadates (KV3O8 and possibly KVO3), and to the decrease in the amount of V2O5. The TiV K catalysts are more active and selective in the ODH of propane, and more active in isopropanol dehydrogenation to the acetone (thus more basic) than the TiK V samples.