Photocatalytic degradation of hexane vapors in batch and continuous systems using impregnated ZnO nanoparticles

The decomposition of gas-phase hexane in air streams by immobilized nanoparticles of TiO2 and ZnO onto Perlite and Poraver (R) granules was studied. Photocatalytic degradation experiments were conducted in batch and plug flow continuous photoreactors at a UV irradiation of 254 nm. The TiO2 and ZnO samples had similar hexane degradation rates and conversion percentages in batch tests. Photolysis contributed to 58% of the photodegradation phenomena. The hexane batch degradation velocities that normalized to impregnated support mass were similar for both semiconductors. When normalized to A(BET) of the impregnated support, ZnO allowed a higher hexane degradation velocity than TiO2. Maximal mineralization of hexane in batch tests was 98% and 57% for TiO2 and ZnO sytems, respectively. The production of by-products was identified at minute 30 and a pathway of hexane degradation was suggested, mainly ketones and secondary alcohols being identify. For continuous experiments, the TiO2 catalyst supported onto Perlite showed degradation velocities at least 74% greater than for the ZnO. However, in terms of the A(BET) normalized velocities; the ZnO impregnated onto Poraver (R) resulted in a better performance than that obtained with TiO2 and ZnO onto Perlite. The impregnated catalyst had favorable conversion rates, but the CO2 produced was undetectable. Overall, the use of TiO2 and ZnO for the degradation of high loads of hexane vapors exhibits good degradation rates in a relatively short time, as well as a high production of by-products. (C) 2012 Elsevier B.V. All rights reserved.