Photodegradation of cyclohexane and toluene using TiO₂/UV/O₃ in gas phase

Volatile organic compounds (VOC) are air pollutants usually found in urban and industrial areas. Heterogeneous photocatalysis is an interesting technique used to degrade these compounds. Several approaches may enhance this process; some studies have shown higher VOC conversions by adding ozone to the experimental system, once ozone increases the number of reactive radicals in the reaction. In this context, this work studied the conversion of cyclohexane and toluene by heterogeneous photocatalysis in gas phase, in the presence of titanium dioxide (TiO₂), UV light, and different concentrations of ozone. For fixed space times from 13.1 to 48.8 s, an average increase of 9% was reached in cyclohexane conversion when comparing the system with maximum concentration of ozone (0.8%) and the system without it. In addition, difference of less than 2% in the conversion of cyclohexane with different moisture fractions was observed. Toluene photodegradation was also analyzed in the presence of ozone and although the conversion was only about 40% for the space time of 25 s, this result was maintained during 4 h of experiment, with no catalyst deactivation as usually reported in the literature for aromatic compounds. Based on the results, ozone addition is an advantageous technique to improve the photodegradation of VOC.