U. Bentrup et al., Infrared characterization of the surface intermediates in the oxidation oftoluene on vanadyl pyrophosphate catalysts, TOP CATAL, 11(1-4), 2000, pp. 139-145
The adsorption and reaction of toluene on vanadyl pyrophosphate catalysts w
as studied by in situ infrared spectroscopy. Strongly adsorbed benzaldehyde
and physically adsorbed cyclic anhydride species were observed at temperat
ures above 523 K. Water formed during reaction generates acid hydroxyl grou
ps which cause a stronger adsorption of benzaldehyde and consecutive oxidat
ion reactions. By co-adsorption of pyridine the acid sites are blocked and
the deeper oxidation is suppressed.