engleski

Photocatalytic oxidation of toluene

Photocatalytic oxidation (PCO) is a promising way for the purification of contaminated air containing organic pollutants (volatile organic compounds, VOC). Photocatalysis is advantageous because the required energy is supplied by the direct absorption of light in UV region at room temperature. Titanium dioxide (TiO2) is the most attractive and efficient semiconductor used today, having high photocatalytic efficiency, stability toward photocorrosion and chemicals, insolubility in water, low toxicity, and low cost. Absorption of UV light excites electrons from the valence to the conduction band, creating electron– hole pairs which make it a strong oxidant. Various photoreactors for the treatment of VOCs in air streams can be used, such as slurry reactor, packed-bed reactor, fluidized-bed reactor, fixed-bed reactor and optical fiber reactor. In this study heterogeneous photocatalysis for the toluene degradation (used as model VOC) in the gas phase on commercial TiO2 catalyst (Degussa, AEROXIDE TiO2, P25) was investigated. For this purpose laboratory annular fixed powder layer photocatalytic reactor (volume 0.5 dm3) was used. Illumination was provided by a commercially available 8 W black light tube located inside the inner tube of the reactor. The reaction products were analyzed on-line every 5 min by a flame ionization detector on a gas chromatograph (GC Varian 3300), allowing detection and quantification of toluene (and organic byproducts) on Carbowax 20M column. The influence of the gas flow rate and the toluene inlet concentration was studied. This work was aimed at describing basic features of the investigated photocatalytic reactor with particular focus on the reactor design and the development of the appropriate mathematical model. The proposed model was verified by comparing the experimental data with theoretical predictions. Generally, a good agreement was achieved, indicating that that proposed model could be successfully used to describe photocatalytic degradation of the cited VOCs in the gas phase using an annular flow reactor.

photocatalytic oxidation; TiO2; toluene

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