UV254nm+185nm光照降解气态甲苯的实验研究

研究了波长为254nm+185nm紫外光照射下,甲苯初始浓度、停留时间、相对湿度、O2浓度等因素对甲苯光降解效率的影响.通过定量UV254nm+185nm光照下体系中O3的产生浓度变化,以及降解过程中中间产物苯和苯甲醛的变化趋势,讨论了甲苯在UV254nm+185nm照射下降解机理.结果表明,甲苯去除率随着O2含量、停留时间的增加而升高;随着初始浓度的增加而降低.与湿度的关系为先急剧升高然后缓慢增加,而后降低,最佳相对湿度在40%~50%.当甲苯初始浓度为16.1mg/m3,O2含量为20%,相对湿度为40%时,体系对甲苯的降解效率为82.2%,降解速率为0.44mg/(m3·s),产生的O3浓度为131.13mg/m3,中间产物苯和苯甲醛的浓度分别为0.086,0.135mg/m3.在反应体系中,甲苯可吸收185nm波长紫外光直接降解,但主要被体系中产生的自由基氧化降解.

Experimental study on UV254nm +185nm phtotodegradation of gaseous toluene

An UV254+185nm lamp was employed to treat gaseous toluene flow. The toluene conversion efficiency under different conditions was discussed, including relative humidity (RH), oxygen level, initial toluene concentrations and retention time. Toluene conversion efficiency increased with the increasing of oxygen level and retention time, but decreased with the higher initial concentration. Moreover, conversion efficiency increased rapidly at first and then decreased slowly while RH increases, with a optimum RH of 40%~50%. When toluene initial concentration was 16.1mg/m3, RH and oxygen level was 40% and 20% respectively, the conversion efficiency of toluene was 82.2% with conversion rate of 0.44mg/(m3×s), while ozone concentration was 131.13mg/m3, benzene and benzaldehyde yielding concentration was 0.086mg/m3 and 0.135mg/m3. The yielding of ozone and intermediate products during phtotodegradation was discussed to probe the degradation mechanism of toluene under UV254+185nm irradiation. Gas phase Toluene can be directly degraded by UV185nm irradiation, but most of it was degraded by radical initialed reactions.