【作者】 丁艳敏；

【导师】 李彩亭；

【作者基本信息】 湖南大学 ， 环境工程， 2009， 硕士

【摘要】 氮氧化物（NO_x）因导致酸雨、光化学烟雾和温室效应等环境问题,已严重危害人类健康,且随着机动车量增加和工业发展,其排放量日趋增大,势必造成生态和环境的严重恶化。因此,消除NO_x污染问题迫在眉睫。目前,NO_x主导控制技术是NH₃选择性催化还原（SCR）,此技术的关键是选择优良的催化剂。分子筛以及改性分子筛由于其出色的活性和选择性被认为是具有实际应用前景的SCR催化剂,而以ZSM-5分子筛为载体负载各种过渡金属的催化剂体系尤为受到关注。HZSM-5是ZSM-5的衍生物,因具有相对合适的孔结构和酸性质,常用作工业固体催化剂的载体。通过添加合适的活性组分或助剂对催化剂载体进行改性,从而提高其对NH₃选择性催化还原NO_x反应的催化性能。本文正是着重于研究此种负载型催化剂,选择合适的催化剂载体、活性组分或助剂,找出最为理想的催化剂载体、活性组分及助剂的复配方式,以期找到一种高效、经济、实用的负载型催化剂,为SCR催化剂的研究及工业化应用提供参考依据。本实验以HZSM-5为载体,在不同制备条件下制备改性分子筛作催化剂。首先采用离子交换法和等体积浸渍法制备Mn改性HZSM-5催化剂,在焙烧温度550℃条件下,制备了不同Mn负载量（0%～10%）的Mn/HZSM-5（550℃）催化剂,发现适量Mn的添加可以提高催化剂的NH₃选择性还原NO的催化性能;对比两种催化剂制备方法所得催化剂的脱硝效果,离子交换法较等体积浸渍法有很大的优越性,以离子交换法制备的5%Mn/HZSM-5催化效果最好。因此,在后续实验中均采用离子交换法制备催化剂。在5%Mn/HZSM-5（550℃）催化剂基础上,通过添加助剂Fe对催化剂进行复合改性,制备了Fe/Mn（摩尔比）为0.10、0.25、0.50、1.0的复合改性催化剂,考察其选择性催化还原NO性能。结果表明:复合改性较单独改性性能更为优越,适量Fe的加入,不仅提高了催化剂的催化活性,而且大大提高了催化剂的热稳定性。（0.25）Fe-Mn/HZSM-5（Fe/Mn摩尔比为0.25）的NO转化率于300℃时最高达到98.31%,在300～500℃范围内NO转化率均保持在90%以上。实验还研究了不同离子交换次序及不同焙烧温度下制备的Mn和Fe复合改性催化剂对NO转化率的影响。结果表明,交换次序先Mn后Fe催化性能最好,550℃为最佳焙烧温度。同时联合运用ESEM、BET和XRD等方法对催化剂进行了表征。研究了O₂、NH₃对（0.25）Fe-Mn/HZSM-5（550℃）催化剂活性的影响,并考察了其在300℃时催化活性与时间的关系。更多还原

【Abstract】 Nitrogen oxides （NO_x） are responsible for causing acid rain, photochemical smog, the greenhouse effect and other environmental problems, that have been serious harmful to human health. With the motor vehicles increase and industrial development, the emissions will be increasing. That will inevitably cause serious ecological and environmental deterioration. Therefore, it is imminent to eliminate NO_x pollution problem. Currently, the technology of Ammonia selective catalytic reduction （SCR） is the dominant technology used to control the pollutants of NO_x, and the key to this technique is to choose an excellent catalyst. Zeolites and modified zeolites are considered to have practical application prospect because of their excellent activity and selectivity, and ZSM-5 zeolites loaded by transition metal have been paid more attention. HZSM-5 is a derivative of ZSM-5, commonly used for industrial solid catalyst carrier due to its relative right pore structure and acid property. The catalyst carrier can be modified by adding a suitable active component or accessory ingredient in order to enhance their catalytic performance of Ammonia selective catalytic reduction. This paper is focused on the study of such supported catalysts, choosing a suitable catalyst carrier, active component or additive and finding the ideal compounding method of them, with a view to finding an efficient, economical and practical supported catalyst to provide reference for the research and industrial applications of the SCR catalyst.In our experiment, HZSM-5 was modified under different preparation conditions. First, HZSM-5 modified by various Mn loadings （0～10wt%） in calcinations temperature of 550℃condition were prepared by ion-exchange method and the isometric incipient impregnation method. It was found: the catalytic performance of the catalysts for Ammonia selective catalytic reduction of NO could be improved by adding amount of Mn. We compared the denitration effects of catalysts which were prepared by ion-exchange method and the isometric incipient impregnation method, and found that ion-exchange method had great advantages. 5%Mn/HZSM-5（550℃） prepared by ion-exchange method was the best catalyst. Therefore, the catalysts in follow-up experiments were prepared by ion-exchange method. The complex modified catalysts were prepared based on 5%Mn/HZSM-5（550℃） by adding additives Fe, and the Fe/Mn（molar ratio） of 0.10, 0.25, 0.50 and 1.0. The performance of their Selective Catalytic Reduction of NO was examined. The results showed that the performance of composite-modified cataalysts was more superior than that of single-modified. Adding amount of Fe not only improved the catalytic activity of the catalysts, but also greatly enhanced the thermal-stability of the catalysts. The activity of （0.25）Fe- Mn/HZSM-5 （Fe/Mn molar ratio of 0.25） reached 98.31% at 300℃, and remained above 90% when the temperature was 300～500℃. The effect of Mn and Fe composite modification catalysts with different ion-exchange order and different calcinations temperature were also investigated. The results showed that the best ion-exchange order was adding Mn firstly and then adding Fe, and the optimal calcination temperature was 550℃. A combination of technigues such as ESEM, BET surface area and X-ray diffraction were used to characterize the catalysts. And through further analysis, the impact of O2, NH₃ on the catalytic activity of （0.25）Fe-Mn/HZSM-5（550℃） catalyst were studied. We also studied the relationship between the catalytic activity and the reaction time at 300℃.更多还原