DRIFTS and transient-response study of vanadia/titania catalysts during toluene partial oxidation

Abstract

The work was aimed on the determination of the role of bulk V 2 O 5 present in vanadia/titania catalysts for toluene partial oxidation. Two catalysts with 1.8 and 11.1 wt% of V were studied by in situ DRIFTS and transient-response methods. Bulk V 2 O 5 was found by FT-Raman spectroscopy only in the 11.1 wt% V/TiO 2 catalyst while monolayer vanadia species (monomeric and polymeric) in both samples. Toluene interaction in the presence of gaseous oxygen showed that the selectivity to benzaldehyde and benzoic acid was similar for the two catalysts. The nature of adsorbed species was also similar. Toluene interaction with the oxidised samples in the absence of gaseous oxygen showed rapid formation of coordinatively adsorbed benzaldehyde ($1625 cm À1) and benzoate/carboxylate species (1600-1400 cm ). Additionally, large quantities of gaseous products (CO x , benzaldehyde, H 2 O) were obtained with the former catalyst, while almost none with the latter. Thus, bulk V 2 O 5 could supply oxygen for the monolayer vanadia species easily reducible by toluene. This oxygen is required for the product formation and desorption.

Catalytic self-sustained combustion of toluene and reaction pathway over CuxMn1-xCe0.75Zr0.25/TiO2 catalysts

“…This phenomenon also testifies that the toluene is adsorbed on CuCZ/T surface via the −CH 3 rather than the aromatic ring, because the interaction between the aromatic ring of toluene and the surface of TiO 2 can lead to an obvious blue shift by forming π-complex [10]. The negative band at 3671 cm −1 and the band at 3593 cm −1 are caused by the surface hydroxyl group interacting with the methyl group of toluene [31], and it confirmsthe methyl group of toluene is adsorbed on catalyst once again.…”

Partial oxidation of toluene to benzaldehyde and benzoic acid over model vanadia/titania catalysts: role of vanadia species

“…It should be mentioned that in anaerobic conditions toluene can be oxidised by the oxygen of the catalyst [33]. However, the reactivity of the 2.6 ML V/TiO 2 and 0.37 ML V/TiO 2 catalysts was found different.…”

“…Gaseous BA and CO x formation is observed only for the 2.6 ML V/TiO 2 catalyst, but not for the 0.37 ML V/TiO 2 one. In the latter case, DRIFTS studies found that adsorbed BA as well as CO x formation intermediates are formed and retained on the surface, but either gas phase oxygen or oxygen of the bulk V 2 O 5 are necessary for their desorption [33].…”

Complementary phenomenological and spectroscopic studies of propane sensing with tin dioxide based sensors

“…Although, the DRIFT method is a tool for the characterization of the surface adsorbed species, the phenomena related to the observation of the gaseous molecules in the space between the grains were reported in the literature by Rainone et al, for toluene [17] and Harbeck et al [3] for carbon dioxide.…”