Photocatalytic degradation of gaseous benzene in air streams by using an optical fiber photoreactor

A batch-type photoreactor contains a bundle of TiO2-coated quartz fiber was employed for the photocatalytic oxidation of gaseous benzene in air stream. For experiments conducted with initial benzene concentration of 20 ppmv, about 80% of benzene was decomposed in the optical fiber photoreactor after 4 h of ultraviolet (UV) irradiation with the presence of 5% relative humidity. The reaction order of light intensity to the decomposition rate is varied with longitudinal position of optical fiber and the calculated overall order was calculated to be 0.74. A maximum quantum yield (Φ) of 0.5 was achieved for experiments operated in the optical fiber photoreactor, comparing to a maximum quantum yield of 3.55×10−3 for those conducted in an annular fixed-film photoreactor under similar operational conditions. The reaction products adhered on the fiber were sampled at various longitudinal positions and identified by the FTIR spectrum. The gaseous reaction intermediates were detected using a GCD/MS. Phenol was identified to be the major intermediate generated at the early stage of benzene decomposition, and the final products were found to be CO2, CO and H2O. Deactivation of TiO2 photocatalyst coated on the optical fiber reactor was found to be much slower than those coated on annular photoreactor.