FTIR study of adsorption, thermal reactions and photochemistry of benzene on powdered TiO2

The adsorption, thermal reactions, and photochemistry of benzene on powdere d TiO2 have been investigated using Fourier-transform infrared spectroscopy . Benzene is adsorbed with its pi electrons interacting with the surface Ti 4+ ions, and is stable even when the TiO2 temperature is increased to 400 d egreesC. However, it is subject to thermal decomposition to H2O(g), CO(g) a nd CO2(g) in the presence of O-2 and the dissociation occurs below similar to 225 degreesC. With the aid of an adsorption study of phenol and iodobenz ene, it is found that phenoxy groups are generated on the surface in the ph otooxidation of benzene on TiO2 and the amount greatly increases in the pre sence of H2O or O-2. Other surface products containing carbonyl or carboxyl ate groups are produced as well for benzene photoreaction in O-2. The prese nt in situ study shows that the products extracted using solvents from TiO2 catalysts after photooxidation of benzene in previous investigations may n ot reveal the real products formed on the surface during photoillumination processes.