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铜基催化剂催化氧化单质汞性能及机理研究
Alternative TitleCatalytic performance and mechanism study on catalytic oxidation of gas-phase Hg0 over copper based catalysts
王海蕊
Subtype硕士
Thesis Advisor朱廷钰 ; 徐文青
2013-05-01
Degree Grantor中国科学院研究生院
Degree Discipline化学工程
Keyword燃煤烟气   铜   二氧化钛   催化氧化   汞
Abstract汞是剧毒重金属,具有持久性、易迁移性和高度生物富集性等特点,汞污染排放及控制已成为全球关注的热点。煤燃烧是最主要的人为汞排放源之一,单质汞(Hg0)具有较高的挥发性与较低的水溶性,是最难控制的汞形态。采用催化氧化法将单质汞氧化为二价汞,利用后续脱硫设备除去是目前燃煤烟气汞控制的发展方向,因此开发低成本高活性的单质汞氧化催化剂具有实际应用意义。 本论文以锐钛矿纳米TiO2为载体,以Cu、Mn、Fe、Co、Ce等过渡金属的氧化物作为活性组分,采用浸渍法制备一系列负载型催化剂,考察其对Hg0的催化氧化性能。筛选出活性最佳的CuO/TiO2催化剂,考察活性组分负载量、空速、温度、HCl浓度、气氛等因素的影响,并对催化剂进行N2-吸附/脱附、X射线衍射、X光电子能谱、Hg-程序升温脱附、红外光谱等表征,推测Hg0在不同气氛中的反应机制。在CuO/TiO2催化剂研究基础上制备了CuCl2/TiO2催化剂,考察催化剂负载量及烟气成分对Hg0氧化效果的影响,得到以下结果: (1)筛选了用于燃煤烟气中单质汞催化氧化的催化剂,阐明了Hg0催化氧化的影响因素。低温下CuO/TiO2催化剂活性最高,负载量为7%时活性最佳。较小的空速,较大的HCl浓度有利于Hg0的氧化。Cu在催化剂表面分散性好,以CuO的形式存在。 (2)考察了烟气成分对CuO/TiO2催化剂Hg0氧化效率的影响,探讨了不同气氛中Hg0的氧化机理。含氯体系中HCl会极大地促进Hg0的氧化,氧化路径遵循部分Deacon机制,即HCl在催化剂表面生成活性Cl,并将Hg0氧化。不含氯体系中,有氧环境中SO2、NO均可促进Hg0的氧化,二者共存可显著提高Hg0氧化效率,NO、SO2与O2共存时在催化剂作用下与汞反应生成HgO及HgSO4等汞化合物。 (3)制备并考察了CuCl2/TiO2催化剂上Hg0的氧化效率。CuCl2/TiO2催化剂可在不含氯体系中表现出比CuO/TiO2催化剂更优异的催化性能,7%负载量的催化剂分散性较好,比表面积较大,催化活性较高,具有较好的活性和稳定性。 本论文的研究工作为Hg0催化氧化技术提供了实验依据,为低成本高活性燃煤烟气汞氧化催化剂的开发提供了技术储备。
Other AbstractMercury, as a highly toxic heavy element, has received considerable attention from environmental researchers due to its high volatility, environmental persistence, and robust bioaccumulation properties. Coal combustion is the largest source of mercury emissions from anthropogenic. Hg0 is the most difficult species to remove, because of its high volatility and low aqueous solubility. As a result, the study on Hg0 removal from flue gas is becoming increasingly important. The catalytic oxidation method could convert Hg0 to Hg2+, which could be controlled by desulfurization system. Developing high-efficiency and low-cost catalyst is necessary for control of mercury. In this work, the catalysts were prepared by impregnation method and anatase TiO2 nanoparticles were used as a support, Cu、Mn、Fe、Co、Ce were used as active component. The catalytic activities of different catalysts were tested and CuO/TiO2 was chosen for its good performance, then the influences of loading of CuO, space velocity, temperature and atmosphere on catalytic oxidation efficiency were systematically investigated. The X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Hg-temperature programmed desorption (Hg-TPD), infrared spectroscopy (FTIR) and other characterization were used to investigate the reaction mechanism. The CuCl2/TiO2 catalysts were prepared and its catalytic activities were investigated with the comparation to CuO/TiO2. The influences of CuCl2 loading and flue gas composition on catalytic activities were tested. The following results are obtained: (1) The catalytic oxidations of Hg0 by the catalysts were investigated under simulated flue gas conditions and the impact factors on catalytic oxidation efficiency were clarified. The results indicated that CuO/TiO2 showed highest activity in the low temperature and 7% is the optimum loading. The low space velocity and high HCl concentration favored the oxidation efficiency of Hg0. Cu was well dispersed on the surface of TiO2 and it was existed as CuO. (2) Hg0 oxidation efficiency over Cu/TiO2 catalyst in different flue gas composition was investigated, and the reaction path was dicussed. In Chlorine containing system, HCl would greatly promote Hg0 oxidation, which followed the patial Deacon mechanism in which HCl could generate active chlorine atoms to improve Hg0 oxidation. In chlorine free system, NO and SO2 could promote Hg0 oxidation with O2, for they could react with Hg0 and produce HgO and HgSO4. (3) The Hg0 oxidation efficiency on CuCl2/TiO2 catalyst was investigated. The CuCl2/TiO2 catalyst exhibited better catalytic performance than CuO/TiO2 in chlorine free system. The catalyst contained 7% CuCl2 was highly dispersed, which had large specific surface area and higher catalytic activity and stability. The basic data in this study are significant for mercury catalytic oxidation, as well as the technique support for the removal of Hg0 from coal fired flue gas.
Pages81
Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/8350
Collection研究所(批量导入)
Recommended Citation
GB/T 7714
王海蕊. 铜基催化剂催化氧化单质汞性能及机理研究[D]. 中国科学院研究生院,2013.
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