Photocatalytic degradation of benzene in oxygen-containing gaseous feed streams was investigated using titania and platinized (0.1 wt.-%) titania photocatalysts. The titania catalyst was synthesized using sol-gel techniques. Results of this study indicate that, when using this particular photocatalyst, benzene was oxidized to carbon dioxide and water without forming any detectable organic reaction products in the reactor effluent, although only some of the benzene reacted. Both the overall conversion of benzene and its mineralization were improved by platinizing the titania. When the titania catalyst was platinized, both photocatalytic and thermocatalytic reactions were promoted. Rates of photocatalytic reactions were significantly enhanced at reaction temperatures between 70 and 90

Hollow metal oxide fibers [TiO2 and Fe2O3] have been prepared by using activated carbon fibers [ACFs] as the templates, through a simple impregnation and heat treatment. The resulting products, as compared to ACFs, possessed not only a similar morphological feature upward to the micrometer scale but also different surface nanostructures with unique morphology. The TiO2 fibers displayed overlapped “wormlike” surface and a hierarchical structure with two distinguishable layers, the inner layer and the outer layer, which were composed of the particles of 7 and 15 nm, respectively. It was also found that the reaction temperature had a significant effect on the TiO2 surface morphology. The Fe2O3 fibers exhibited a rough and crinkle-like surface and were also composed of hierarchical particles. Both TiO2 and Fe2O3 fibers possessed the hierarchical pore structure with mesopores in the walls of the large hollow channel. Such porous architecture favored the resultant TiO2 with better apparent photoactivity than P25 titania for degradation of gaseous acetone and would also make the materials useful for further application in other fields.

The grafting reaction of tetraneopentyl titanium on the surface of MCM-41 mesoporous molecular sieves dehydroxylated preliminary at 500 ◦C leads to formation of the well-defined bigrafted surface complex (≡Si–O)2Ti(CH2CMe3)2. On reaction with water or alcohol, the neopentyl ligands can be replaced selectively by alcoxy or hydroxy. On calcination at 500 ◦C, a well-dispersed titanium oxide supported on MCM-41 is obtained. In situ FTIR, DRS, and XAFS characterizations suggest that titanium is present as isolated tetrahedral species on the surface of MCM-41. This solid was used for the photocatalytic oxidation of ethylene in oxygen under UV irradiation, and its activity was compared to that of Ti-MCM-41 prepared by direct hydrothermal synthesis. The higher activity of the samples prepared by reaction with the organometallic complex is attributed to the good dispersion of titanium on the surface of MCM-41.

Superior photocatalytic activity and durability of Pt/TiO2 for decomposing volatile organic pollutants (typically aromatic compounds) have been obtained by adding trace H2 into an O2-rich photooxidation system. The order of photodegradation efficiencies for volatile organic compounds is cyclohexane < acetone < benzene < toluene < ethylbenzene. Exceptional stability of Pt/TiO2 for benzene photodegradation is still maintained after 22h of testing, by the repeated use of the catalyst four times. The promoting effects of H2 in the photocatalysis were studied by infrared spectroscopy (IR), spin-trapping electron paramagnetic resonance (EPR) and surface photovoltage spectroscopy (SPS). Results demonstrated that the introduced H2 has several beneficial effects on heterogeneous photocatalysis, namely, a comparatively clean surface of Pt/TiO2 with no persistent aromatic intermediates, an increased number of surface hydroxyl radicals in the photocatalytic process, and an enhanced separation efficiency of photogenerated electron–hole pairs. A mechanism is proposed to elucidate the promoting effect of H2 on the photooxidation of volatile organic pollutants over Pt/TiO2.

Photocatalytic surface sites on SO42−/TiO2 were investigated by pyridine adsorption and in situ Fourier transform infrared (FT-IR) spectroscopy. Results revealed that the sulfate-modification not only increased the number of strong Lewis acidic sites, but also induced a large amount of strong Brønsted acidic sites on the surface of TiO2. Pyridine molecules were chemically captured on Brønsted and Lewis acidic sites on the SO4 2−/TiO2 surface. These pyridine molecules were progressively decomposed to final products of CO2 and H2O under actual photocatalytic conditions. The high photocatalytic performance of SO42−/TiO2 can be explained by the improved surface acidities that favor the adsorption of both oxygen and pyridine molecules. Moreover, the Lewis acidic sites could react with H2O and was then converted to Brønsted acidic sites, leading to the activation of the water. This conversion promoted the formation of hydroxyl groups on the catalyst surface, which could also contribute to the high photocatalytic reactivity of SO42−/TiO2.