Photocatalytic ethylbenzene degradation associated with ozone (TiO2/UV/O3) under different percentages of catalytic coating area: Evaluation of process parameters

Abstract

Over decades heterogeneous photocatalysis has been successfully applied to degrade a wide range of pollutants. Despite it, when aromatic volatile organic compounds (VOCs) are treated, generally, challenges such as low efficiency and photocatalyst deactivation are faced. In this scenario, the association between heterogeneous photocatalysis and ozone (TiO2/UV/O3) has emerged as an alternative to overcome such issues, although it has not yet been applied to ethylbenzene removal from gaseous streams. In this work, gas-phase ethylbenzene degradation (73 ppmv) by UV radiation, O3, UV/O3, TiO2, TiO2/UV, TiO2/O3, and TiO2/UV/O3 processes was evaluated. The influence of parameters such as relative humidity (26–80%), space-time (130, 74, 52, and 29 s), ozone concentration (3.6, 4.2, and 5.5%), and percentage of catalytic coating area (50, 70, 90, and 100%) on ethylbenzene removal was investigated. Relative humidity from 26 to 50% did not affect ethylbenzene degradation significantly and TiO2/UV/O3 enhanced its removal up to 87.7% and 22% when compared to the TiO2/UV and the UV/O3 processes, respectively. A maximum ethylbenzene conversion of 98% was also reached at 130 s, 70% of TiO2 coating area, and 5.5% of ozone. We found that, in the TiO2/UV/O3 system, reactions on the catalyst surface and in the gas bulk were both important, thus a 70% of TiO2 coating area was obtained as the best configuration. Furthermore, catalyst stability was assessed by a time-on-stream experiment and TiO2/UV/O3 maintained the average ethylbenzene conversion at 75% during 50 h. TGA/DTGA and FTIR analyses allowed the identification of possible compounds adsorbed on the catalyst surface after reactions.