TiO_2柱撑膨润土光催化气相甲苯的活性研究:湿度对活性的影响与催化剂结构的关系  

Catalytic Activity of TiO_2 Pillared Bentonite for Degradation of Gaseous Toluene:Relationship Between the Effect of Humidity and the Catalyst Structure

作　　者：金苏君[1] 陈侠胜[1] 李爽[1] 张兴旺[1] 沈学优[1] 

机构地区：[1]浙江大学环境科学系,杭州310028

出　　处：《环境科学》2008年第12期3331-3336,共6页Environmental Science

基　　金：国家自然科学基金项目(20621140003;20677048;90610005)

摘　　要：采用溶胶法合成TiO2柱撑膨润土复合光催化剂.N2吸附-脱附(BET)结果表明,573、673、773 K热处理后的催化剂,比表面积分别为140.15、110.13、88.38 m2/g.在气相光催化甲苯的连续系统中,研究湿度对催化剂活性的影响.结果表明,在研究范围内,水分子与甲苯在催化剂表面发生竞争吸附,导致光催化活性随着湿度的增加而降低.光催化反应符合L-H模型.573、673、773 K热处理后的催化剂,对水蒸气的吸附常数分别为2.8×10-5、4.1×10-5、1.8×10-4m3.mg-1.573 K热处理后的催化剂,在较低湿度条件下其催化活性不及673 K、773 K热处理后的催化剂,在高湿度下其活性却最佳,即它抗湿度影响的能力最强.采用热解析法测得了催化剂对甲苯的吸附性,当相对湿度从25%增至75%时,573、673、773 K热处理后的催化剂对甲苯的吸附量分别从184.8、130.5、77.6μg/g降到3.25、1.92、1.65μg/g.随着比表面积的增加,催化剂对污染物的吸附性能增加,因而相应的表观水蒸气吸附常数减少,抗湿度影响的能力增强.实验结果表明在TiO2柱撑膨润土光催化气态污染物的实际应用过程中,要考虑环境湿度和催化剂结构,选择环境湿度下催化性能最佳的催化剂.Titania pillared bentonite was prepared by the sol method. The results of N2 adsorption-desorption showed that the specific surface areas of the catalysts calcined at 573, 673 and 773K were 140.15, 110.13 and 88.38 m^2/g, respectively. Their catalytic activities were evaluated for the gas phase degradation of toluene. The effects of humidity on the activity were studied in a continuous system. Results indicated that competitive adsorption between toluene and water molecules occurred on the catalyst surface, thus the photoactivities decreased with the increasing humidity. The photodegradation matched well with the Langmuir-Hinshelwood （L-H） kinetic model, and the adsorption constants of water for the catalysts calcined at 573, 673, and 773 K were 2.8 ×10^- 5 , 4.1 × 10^-5 and 1.8 × 10^- 4 m^3 . mg^- 1 , respectively. The photoactivity of the catalyst calcined at 573K was worst under low humidity but was best under high humidity compared with those of the catalysts calcined at 673K and 773K, suggesting it was most capable of resisting the impact of humidity. The thermal desorption was adopted to analyse the adsorption capability of toluene on catalysts. As the relative humidity increased from 25 % to 75 % , the adsorption amount of toluene for the catalysts calcined at 573, 673, and 773K decreased from 184.8 to 3.25μg/g, 130.5 to 1.92 μg/g, 77.6 to 1.65 μg/g, respectively. Adsorption capability of catalysts increased with the specific surface area, thus the apparent adsorption constant of water was reduced and the ability to resist the effect of humidity was enhanced. Experimental results indicate that during practical application of titania pillared bentonite for gaseous pollutants degradation, the environmental humidity and catalyst structure should be considered to screen out the catalyst with best activity.

关 键 词：TiO2柱撑膨润土 比表面积 湿度 催化活性 

分 类 号：X51[环境科学与工程—环境工程]