School of Chemical Engineering, UNICAMP - University of Campinas, Av. Albert Einstein 500, Cidade Universitária, Campinas, Brazil.
Environ Sci Pollut Res Int. 2019 Feb;26(5):4234-4241. doi: 10.1007/s11356-018-2484-2. Epub 2018 Jun 11.
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 (TiO), 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.
挥发性有机化合物（VOC）是通常在城市和工业区发现的空气污染物。多相光催化是一种用于降解这些化合物的有趣技术。几种方法可以增强这个过程；一些研究表明，通过向实验系统中添加臭氧，可以提高 VOC 的转化率，因为臭氧增加了反应中的反应性自由基的数量。在这种情况下，这项工作研究了在气相中通过多相光催化、二氧化钛（TiO）、紫外光和不同浓度的臭氧来转化环己烷和甲苯。对于固定的空间时间从 13.1 到 48.8 s，当比较具有最大臭氧浓度（0.8%）的系统和没有臭氧的系统时，环己烷转化率平均提高了 9%。此外，在不同水分分数下，环己烷转化率的差异小于 2%。还分析了臭氧存在下的甲苯光降解，尽管在 25 s 的空间时间下转化率仅约为 40%，但在 4 小时的实验过程中，转化率保持不变，这与文献中通常报道的芳香族化合物的催化剂失活情况不同。基于这些结果，臭氧的添加是一种提高 VOC 光降解的有利技术。
