硝酸与硝基苯在SiO_2表面的光化学反应

Photochemical reactions of HNO_3 and nitrobenzene on SiO_2 films

文章采用傅里叶变换红外光谱仪(Fourier transform infrared spectroscopy,FTIR)和高效液相色谱仪(high performance liquid chromatography,HPLC)研究了308nm光照下硝酸(HNO_3)和硝基苯分别在气相及SiO_2表面的光化学反应。探究了光照时间、硝基苯初始浓度和相对湿度(relative humidity,RH)等因素对反应的影响。结果表明:无论有无水汽,无光照条件下HNO_3和硝基苯在气相和SiO_2表面均不直接发生反应;308nm光照下均反应生成对硝基苯酚(p-NP),当有水汽时,水汽会促进反应的进行;随着光照时间、硝基苯初始浓度和RH的增加,气相和SiO_2表面产生的p-NP浓度均呈指数增加;200Pa HNO_3和80Pa硝基苯,在RH=0、25℃,光照90min条件下,SiO_2表面产生的p-NP浓度约是气相的2.17倍,SiO_2的表面效应在HNO_3与硝基苯的反应中起主要作用。

The 308 nm photochemical reactions of nitric acid(HNO 3)and nitrobenzene in the gas phase and on the SiO 2 films were investigated by Fourier transform infrared spectroscopy(FTIR)and high performance liquid chromatography(HPLC).The influence of illumination time,nitrobenzene initial concentration and relative humidity(RH)on the photochemical reactions was studied.The results showed that gaseous HNO 3 did not directly react with nitrobenzene in the gas phase or on the SiO 2 films in the dark regardless of the water vapor.And the p-nitrophenol(p-NP)was formed under 308 nm UV irradiation,when water vapor was introduced into the reactor,water vapor promoted the photochemical reactions of HNO 3 and nitrobenzene.The p-NP formed from the reactions of HNO 3 and nitrobenzene in the gas phase and on the SiO 2 films increased exponentially with the increase of illumination time,nitrobenzene initial concentration and RH.When HNO 3 initial concentration was 200 Pa and nitrobenzene was 80 Pa,the illumination time was 90 min,the RH was 0 and the temperature was 25℃,the concentration of p-NP formed from the reactions of HNO 3 and nitrobenzene on the SiO 2 films was about 2.17 times higher than that in the gas phase.Surfaces effect played a leading role in the reactions of HNO 3 and nitrobenzene on the SiO 2 films.