Advanced Synthesis and Characterization of Vanadia/Titania Catalysts through a Molecular Approach

Vanadia/titania catalysts were synthesized by the equilibrium deposition filtration (EDF) method, which is a synthesis route that follows a molecular-level approach. The type of interfacial deposition as well as the interfacial speciation of the deposited oxo-V(V) species were determined by means of a model that takes into account experimental proton-ion curves and adsorption edges. It is shown that at pH >= 9.5, the deposition proceeds exclusively through the formation of mono-substituted inner sphere monomeric species in an umbrella-like Ti-OV(OH)(2)O configuration, whilst with lowering of the pH, a second species, namely the disubstituted inner sphere quadrameric species in a (Ti-O)(2)V4O10 configuration possessing two mono-oxo V=O and two di-oxo V(=O)(2) terminations gradually prevails, which is in co-existence with the monomeric species. Raman spectroscopy is used for verifying the solution speciation, which is different compared to the interfacial speciation of the deposited oxo-V(V) species. Furthermore, in situ Raman spectroscopy was used to verify the model-predicted interfacial speciation of the deposited oxo-V(V) species and to monitor the temperature-dependent evolution up to 430 degrees C. Hence, a controlled formation of a specific vanadia species on a titania surface is enabled, which, depending on the synthesis conditions, can result in specific catalyst characteristics and thus possibly different catalytic behavior for a specific reaction.

Automated summary

Vanadia/titania catalysts were synthesized using the equilibrium deposition filtration method, allowing for controlled formation of specific vanadia species on the titania surface. This may result in different catalytic behaviors for specific reactions, depending on synthesis conditions. Raman spectroscopy was used to verify solution speciation and monitor temperature-dependent evolution of the deposited oxo-V(V) species.