高效降解溴代持久性有机污染物的碳纳米管负载催化剂制备及作用机理研究

Great concerns about brominated persistent organic pollutants are strongly related to the increasing use of brominated flame retardants and the rise in bromine levels in waste combustion that should presumably follow. Many methods have been applied to destroy these toxic pollutants. Among these catalytic decomposition has been proved to be one of the most viable and economic approach due to its low destruction temperature and its excellent selectivity toward the formation of harmless by-products. Typical brominated organic pollutant bromophenol has been chosen as the model pollutant in this study which is well known as the precursor of polybrominated dibenzo-p-dioxins and polybrominated dibenzofurans in combustion process. Decomposition of bromophenol was investigated over a series of vanadium, cerium and nickel metal oxides supported by carbon nanotubes. Emphasis was put on the investigation of active phase and preparing method including stirring time, pH value, calcinating time and temperature on its decomposition efficiency and stability. A kind of method that would facilitate the catalyst to maintain high specific area, controllable pore system, good dispersion of active phase and enrichment of surface mobile oxygen species was optimized and proposed in order to reach a high destruction efficiency of brominated pollutants at relatively low temperature. In addition, LC and GC-MS was used to identify the intermediates and XPS, FT-IR and ESR analysis was carried out to characterize the surface properties and thus the decomposition mechanism over metal oxides based catalysts was revealed. Above all, vanadium-cerium-nickel composite metal oxides supported by carbon nanotubes was an efficient and promising catalyst for the destruction and detoxification of brominated pollutants in gas phase.

溴代持久性有机污染物引发的环境和健康问题引起了全球的广泛关注。催化分解技术具有无毒害副产物生成，高效、低耗等特点，是去除气相中卤代有机污染物最有效的方法。本研究拟选取溴代二噁英的前体物溴酚为研究对象，以具有良好吸附性能和分散能力的碳纳米管为载体、活性强的V2O5为主催化组分、可降低活化温度的CeO2和可增效的NiO为辅助调控组分，制备碳纳米管负载型复合金属氧化物催化材料，考察制备工艺对催化剂形貌和成分的影响，构建催化降解溴代污染物效果和稳定性的评价体系，获得可在低温条件下实现溴代污染物高效分解的碳纳米管负载型材料。并基于LC和GC-MS等分析技术和XPS、FT-IR和ESR等表征手段，深入揭示碳纳米管负载金属氧化物材料对溴酚的催化分解机理。本研究研制的碳纳米管负载型复合金属氧化物催化剂可用于低温条件(150-250℃)下去除气相中的溴代污染物，具有良好的应用前景。

持久性有机污染物引发的环境和健康问题引起了全球的广泛关注。催化分解技术具有无毒害副产物生成，高效、低耗等特点，是去除气相中卤代有机污染物最有效的方法。本研究考察了活性炭负载型催化剂的制备工艺，优化得到能够提高过渡金属氧化物活性组分分散性的催化剂，并对其催化降解氯苯的机理进行了剖析。V2O5-NiO/AC催化剂对烟气中低浓度六氯苯（80μg/Nm3）在200 oC时具有较高的催化氧化效率，降解率为99.87%。新兴碳材料碳纳米管负载V2O5和NiO催化剂具有比表面积大，活性组分分散程度高、抗中毒性和稳定性强等优点，在中高温320 ℃以上条件下可以高效地将高毒性的环境污染物邻溴苯酚完全降解。原位DRIFT实验研究表明反应稳态时催化剂中Ni大部分处于氧化态(即Ni2+)，反应后催化剂中有部分的Ni2+被还原成NiO，反应过程中的活性位是处于还原态和氧化态的Ni。基于镍氧化物表面存在大量的氧空位缺陷，吸附氧后接受电子生成超氧化离子和氧离子，有利于污染物的氧化降解。最后制备了复合载体负载过渡金属氧化物的催化材料V 2O5 / CNTs - TiO2，碳纳米管的添加，可以有效抑制TiO2的团聚。其较高的催化性能归因于碳纳米管与TiO2间存在的相互作用，两者之间形成的CNTs // TiO2 异质结促进了碳纳米管长程共轭π轨道电子向π轨道跃迁以及TiO2中O的n轨道电子向碳纳米管的π轨道的跃迁，而也增强了样品的电子吸收能。本研究研制的碳基负载型复合金属氧化物催化剂可用于较宽温度窗口去除气相中的溴代和氯代污染物，具有良好的工业应用前景。