【作者】 曾丽萍；

【导师】 张国强； 张泉；

【作者基本信息】 湖南大学 ， 供热、供燃气、通风及空调工程， 2012， 博士

【摘要】 室内空气污染已成为世界各国关注的环境问题,苯作为一种常见的室内空气污染物,已经被国际癌症研究机构确认为有毒的致癌物质,对其有效处理受到国内外的广泛关注。光催化技术利用光催化氧化生成的电子-空穴对及一系列的活性氧物质去除大部分难降解有机污染物,在去除气液相难降解的有机污染物领域受到重视。本文首先制备了一种具有光催化氧化活性的碳纳米管/二氧化钛/壳聚糖(CNTs/TiO2/CS)催化薄膜,然后针对室内污染物苯,研究催化薄膜对苯的光降解机理及其降解室内苯的数学模型,并通过实验研究验证模型的正确性,分析相对湿度、光强、气体流速及污染物的初始浓度对室内苯光降解的影响,最后结合室内空气品质(IAQ)模型和建材散发VOCs的模型,探讨家用净化空调的性能研究。本文研究内容及结论分述如下：采用溶胶-凝胶法制备了碳纳米管不同掺杂量的碳纳米管/二氧化钛复合材料,然后再加入交联剂-壳聚糖,获得了CNTs/TiO2/CS催化薄膜。表征结果表明,二氧化钛粒子包裹在碳纳米管壁上,碳纳米管/二氧化钛的复合材料分散在壳聚糖的矩阵中。以室内苯为污染气体,研究了CNTs/TiO2/CS催化薄膜的光催化活性,发现碳纳米管的掺杂量(质量比)为2%(CNTs(2%)/TiO2/CS时,其催化活性最佳。通过红外光谱与气-质联用分析了CNTs/TiO2/CS薄膜光催化氧化苯的机理,得出气相苯光催化氧化的中间产物为：丙烯醛、乙酸乙酯、十一烷烃、4-羰基-甲基-苯乙酮、十二烷烃、2,4,-二异丁基苯酚和二十一烷烃,主要的中间产物是乙酸乙酯和十一烷烃。根据苯的光催化氧化反应的基元反应,获得了苯光催化氧化的速率方程,并结合LSSE光辐射模型计算了催化剂表面的光照强度；以平板型反应器作为光催化氧化苯的反应器,依据质量守恒定律构建了气相苯在室内光催化氧化模型。模型中考虑了光强、气体流速、相对湿度及污染物的初始浓度这四个因素。采用单因素及多因素实验研究了污染物的初始浓度、光强、相对湿度、气体流速对CNTs/TiO2/CS薄膜光催化氧化苯的影响,并验证了前面建立的数学模型。通过多因素的分析,得到苯的降解效率与各个因素之间的相关性,浓度场、辐射场及流体的传质对苯的光催化氧化存在综合的协调作用。应用多元线性回归分析方法,对光强、气体流速、相对湿度、污染物的初始浓度建立了多元线性关系。通过对这四个因素的敏感性分析,研究了各因素的影响程度,得到了气体流速对CNTs/TiO2/CS薄膜光降解室内苯的影响显著。结合建材VOCs的散发模型与室内空气品质模型,分析了净化装置的去除效率对室内VOCs浓度的影响,并根据这些结果对建材的散发特性及净化空调的性能要求进行研究。研究表明：净化空调的净化效率大于40%后,净化效率对室内VOCs浓度分布影响较小；对于空调的回风量与风速,净化空调的净化效率与净化时间的对数成线性关系,且线性关系受回风量的影响较大。该研究为家用净化空调的设计提供理论参考。更多还原

【Abstract】 At present, the pollution of indoor air has considerably been taken attention abroad as an important environmental problem. Benzene as ubiquitous pollution species in the air is considered to cause cancer by international agency for research on cancer. The effective treating process for decomposing benzene has been increasingly concerned. Photocatalysis as advanced oxidation technology, the use of photocatalytic oxidation of electron-hole pairs and a series of reactive oxygen species can remove most of refractory organic pollutants. It has proved very effective in environmental destruction of VOCs. Photocatalytic active catalyst of carbon nanotubes/TiO2/chitosan (CNTs/TiO2/CS) film was prepared. Degradation mechanism and kinetic model of CNTs/TiO2/CS film for indoor benzene were studied, and experimental study to verify the validity of the model. The influence of the indoor air conditions such as pollutant initial concentration, volumetric flow rate of the pollutant, relativity humidity and irradiance is considered in this model. It combines model of IAQ and model of building materials dissemination of VOCs, and performance of household cleaning air conditioning was studied. The main contents and results in this thesis can be summarized as follows:Different carbon nanotubes content of carbon nano-tube/TiO2(CNTs/TiO2) nanocomposites were prepared using a conventional sol-gel method. To further obtain a uniform catalyst film, chitosan (CS) was used as a crosslinker for the CNTs/TiO2composite. Characterization results show that TiO2particle covered carbon nanotubes surface and CNTs/TiO2composite dispersed in the chitosan matrix. The photocatalytic degaradation of benzene was chosen as a model reaction to evaluate the photocatalytic activities of the catalyst film. An optimum of the synergetic effect was found for a carbon nanotubes doped with2%(weight ratio)(CNTs(2%)/TiO2/CS). The intermediates of the photocatalytic degradation were investigated by FT-IR and GC/MS, of which ethyl acetate and hendecene were two major products and minor intermediate products were acrolein4-carbonyl-methyl-acetophenone,12-alkane,2,4di tert butylphenol and21-alkane. According to the analysis data of FT-IR and GC/MS, the photocatalytic degradation mechanism of the composite film was illuminated.The kinetic equation of photodegradation benzene was established based on elementary reactions of the reaction of the photocatalytic oxidation of benzene. The light intensity of the catalyst surface was calculated by the LSSE light radiation model. A model of photocatalytic oxidation of gas phase benzene was build together with the law of conservation of mass by a flat-plate reactor as photocatalytic oxidation reactor. The influence of the indoor conditions such as light intensities, relativity humidity, flow rates and initial concentrations is considered in this model.The influences of single factor and multi-factor were completed by experimental study on light intensities, relativity humidity, flow rates and pollution initial concentrations. The good agreement between the predictions from the model and the experimental results indicates the validity of the proposed kinetic model. A synergetic effect was found for photocatalytic oxidation benzene among the concentration field, radiation field and fluid mass transfer. Using multivariate analysis method, the relations of geological and influence factors of photodegradation of benzene are set up on light intensity, relativity humidty, flow rate and pollutant initial concentration. The degree effect of different factors is studied by multi-factor sensitivity analysis, and the influence of flow rate is more pronounced for photodegradation of indoor benzen.The effect of the efficiency of photocatalytic purifiers on concentration of VOCs· in indoor was investigated by considering the VOCs emission model of building materials and IAQ model. The results show that:When the purification efficiency of clean air conditioning is more than40%, it is small for influence degree of the purification efficiency on concentration distribution of indoor VOCs. For return air of air-conditioning and wind speed, it is linear relationship between the logarithm of purification time and purification efficiency. Compare to indoor wind speed, effect of return air is significant. These studies provide a theoretical reference design for household cleaning air-conditioning.更多还原