【作者】 黄炯；

【导师】 叶代启；

【作者基本信息】 华南理工大学 ， 环境科学， 2010， 硕士

【摘要】 挥发性有机物(Volatile Organic Compounds,VOCs)来源广泛,危害人类健康,是主要的大气污染物之一。与传统治理技术相比,低温等离子体催化技术具有投资少、效率高、能耗低、操作简单、副产物少等优点,被认为是环境污染物处理领域中最有发展前景的技术之一。但低温等离子体催化技术还存在一些问题需要进一步的研究,如VOCs及臭氧的同时高效去除、气相副产物及气溶胶的分析和协同机制的探讨。采用线板式介质阻挡反应器,结合同时高效去除甲苯及臭氧的催化剂降解甲苯,考察反应条件对甲苯去除的影响,对反应生成的CO、CO2和O3进行定量分析,全面分析甲苯降解的气固相副产物;对催化剂进行表征和分析;分析臭氧和羟基自由基在介质阻挡放电协同催化体系中的作用,提出甲苯的降解机理。主要研究内容和结果如下:(1)氮气气氛下,介质阻挡放电没有产生臭氧,放电产生的高能粒子能有效地降解甲苯,输入电压较高时(>9.0kV),水蒸气对甲苯去除的促进作用大于抑制作用;空气气氛下,介质阻挡放电在去除甲苯的同时产生了高浓度的臭氧,输入电压、湿度及甲苯初始进口浓度对甲苯的去除效率和臭氧的出口浓度有重要的影响。(2)催化剂结合在介质阻挡放电区,能提高了反应器的放电性能;催化剂对催化氮活性物种去除甲苯的促进作用不明显;催化剂负载在发泡镍后端的甲苯及臭氧去除效果都比负载在前端的高;水蒸气的存在不利于甲苯的去除,但能减少臭氧的出口浓度。(3)催化剂结合在等离子体区后可实现甲苯及臭氧的同时去除,输入电压为9.0kV时,甲苯的去除效率达92.8%,在80min内O3的去除效率维持在99%以上;除臭氧外,空气放电产生的其它物种对DBD区后甲苯的催化降解的促进作用不明显。臭氧浓度较高时湿度对甲苯及O3的降解效率的影响都很小。(4)介质阻挡放电-催化降解甲苯生成的多相态产物,是碳平衡较低的原因之一。催化剂结合在等离子体区后,水蒸气的存在有利于CO向CO2转化,减少气相产物的种类,提高碳平衡。甲苯降解的副产物除了带苯环的衍生物(苯甲酸、苯甲醛、苯甲醇等),还包括苯环断裂后形成的小分子产物(丙烷、2-甲基丁烷等、乙醛、甲酸、硝基甲烷等)。在产物分析的基础上,研究了甲苯的降解机理。更多还原

【Abstract】 The emission of volatile organic compounds (VOCs) with extensive sources is one of most important air pollution and harmful to human health. Compared with traditional technologies, non-thermal plasma-catalysis (NTP-catalysis) is considered as one of the most promising technologies for environmental pollution control in recent years, with many advantages such as low cost, high removal efficiency, less energy consumption, simple operation, less by-products etc. However, they still have many drawbacks. However, NTP-catalysis still has some problems to solve such as the simultaneous removal of toluene and ozone, analysis of by-products and investigation of synergetic mechanism.Technology of dielectric barrier discharge (DBD) combined with catalyst which performed efficiently in the simultaneous removal of toluene and ozone was applied for toluene descomposition. Effects of various reaction conditions were investigated. The products such as carbon monoxide, carbon dioxide and ozone were quantitatively analyzed. The products of toluene decomposition in gasous and solid phase were confirmed. In addition, the catalysts were characterized and analyzed. Based on the experimental results, the formation mechanism of products was analyzed. The roles of ozone and hydroxy radical in DBD-catalysis system were analyzed and the degradation mechanism was proposed.The main research contents and results were as follows:(1) DBD did not produce ozone and high energetic particles produced could degrade toluene effectively in N2. With higher input voltage (>9.0kV), the promotional effect of water vapor was greater than inhibitional one on toluene removal with N2 as background gas. High concentration ozone was produced when toluene was removed by DBD with air as background gas. Important effects of input voltage, humidity, as well as the initial toluene concentration on toluene removal and ozone outlet concentration were investigated in air.(2) The performance of dielectric barrier discharge was improved with catalyst in plasma. The stimulation of catalyst on the catalytic removal of toluene by nitrogen active species was not obvious. Removal efficiencies of toluene and ozone were higher with catalyst loaded at the back end of nickel foam than at the front end. Water vapor has a negative effect on toluene removal, but it could reduce the outlet concentration of ozone.(3) High removal efficiencies of toluene and ozone could be realized simultaneously with catalysis in plasma. With input voltage of 9.0kV, the toluene removal efficiency was up to 92.8% and that of ozone was above 99% within 80 min. Other species except ozone produced by air discharge had little contribution to toluene removal in post-plasma. Humidity had little effect on the removal efficiencies of toluene and ozone under higher ozone concentration.(4) The heterogenous products produced in toluene removal by DBD-catalysis were the main cause of low carbon balance. Water vapor was beneficial to the conversion of CO to CO2, which could also reduce the by-products and improve carbon balance with catalyst in post-plasma. By-products of toluene decomposition included ring-retaining substances (benzoic acid, benzaldehyde, benzyl alcohol etc.) and ring-cleavage substances (propane, 2-methylbutane, acetaldehyde, formic acid, nitromethane etc.). Base on the analysis of products, the degradation mechanism of toluene was deduced.更多还原