Applied Catalysis A: General, Vol.244, No.2, 251-263, 2003
Structural and catalytic properties of vanadia-based fibrous catalysts in toluene partial oxidation
Structured vanadia-based catalysts in the form of woven fabrics were successfully synthesised by incipient-wetness impregnation and sol-gel methods. The catalysts were investigated by Raman, X-ray photo-electron spectroscopies as well as high-resolution transmission electron microscopy (HRTEM). The spectroscopic results revealed that the elemental fibres consisted of a silica core covered by vanadia/titania. The modification of fibre silica surface by alumina resulted in a support with an increased dispersion of active vanadia/titania layer. Crystalline anatase was not found to be necessary for the formation of active surface vanadia species. Drying of titania. layer without calcination led to a higher vanadia dispersion on titania. Structured fibrous vanadia-based catalysts demonstrated comparable activity and identical selectivity towards the products of toluene partial oxidation (benzaldehyde and benzoic acid) as granulated vanadia/titania with the same vanadium coverage. The transient response technique was applied to elucidate the role of the support on the active species. Thus, the V2O5/TiO2/SiO2 woven fibre fabrics show promise for hydrocarbon partial oxidation, providing advantages due to its open macro-structure suitable for design of structured catalytic beds.
Keywords:Raman spectroscopy;vanadia;titania;silica;catalysts;fibrous catalysts;structured catalytic bed;toluene partial oxidation;transient response technique