An in situ electron paramagnetic resonance (EPR) study has been carried out for anatase (Hombikat UV100) and rutile TiO(2) nanoparticles at liquid helium (He) temperature (4.2 K) under UV irradiation. Rutile titania was synthesized by ultrasonic irradiation with titanium tetrachloride (TiCl(4)) as the precursor. XRD and Raman results evidence the crystallinity of titania phases. The nature of trapped electrons and holes has been investigated by EPR spectroscopy under air and vacuum conditions. Illumination of TiO(2) powder (anatase and rutile) at 4.2 K resulted in the detection of electrons being trapped at Ti(4+) sites within the bulk and holes trapped at lattice oxide ions at the surface. The stability of electron traps was very sensitive to temperature in both phases of TiO(2). The annealing kinetics of the EPR detected radicals has been studied from 4.2 K to ambient temperature and also for calcined titania particles from 523 to 1273 K.

Potential and limitations of molten alkali metal (Li, Na, and K) chlorides supported on Dy 2 O 3 /MgO were explored for the oxidative dehydrogenation of lower alkanes, such as ethane and propane. The catalysts have high activity and selectivity to olefins compared to conventional catalysts. Optimum performance is obtained with catalysts on which the alkali metal chloride phase is molten under reaction conditions. Lower chloride melting point correlates with higher selectivity. The high selectivity to ethene or propene is attributed to the high mobility of cations and anions, which facilitates desorption of alkene (limiting further oxidation) and the generation of spatially isolated hypochloride anions acting as the active sites for the primary C-H bond activation.

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