论文总字数：20805字

摘 要

氨选择性催化还原NO_x（Selective Catalytic Reduction of NO_x by ammonia， NH₃-SCR）是一种有效的烟气脱硝技术，而在低温下如何实现烟气脱硝是如今研究的重点。本课题以Mn为活性组分，TiO₂为载体，研究制备方法、助催化剂的筛选优化，研制出在高效的低温脱硝催化剂，并对其进行活性评价及NH₃-TPD的表征，研究结果如下：

第一阶段分别采用溶胶-凝胶法，共沉淀法和水热合成法制备Mn/TiO₂催化剂，其中溶胶-凝胶法制得的催化剂的NO_x去除率最高，在200℃时NO_x的去除率达到99%。从NH₃-TPD的表征结果来看，溶胶-凝胶法制得的催化剂的低温和高温脱附峰对应的温度最高，表明其表面酸性位最强；且脱附峰的峰面积最大，表明其酸量最大。由此可知，采用溶胶-凝胶法制得的催化剂活性最高。

第二阶段中采用溶胶-凝胶法制备了Mn-Ce/TiO₂ 、Mn-Cu/TiO₂、Mn-Fe/TiO₂催化剂，考察了助催化剂的加入对催化活性的影响。其中Mn-Fe/TiO₂催化剂达到NO_x最高去除率的温窗最大，在160℃时达到了99%的NO_x去除率，到300℃时才开始下降，温窗远大于其他两种催化剂。从NH₃-TPD的表征结果来看，Mn-Fe/TiO₂催化剂的低温和高温脱附峰对应的温度最高，表明其表面酸性位最强；且其脱附峰的峰面积也略大于其他两种催化剂，表明其酸量最大。由此可知，Mn-Fe/TiO₂催化剂的活性最高。

关键词：氮氧化物 选择性催化还原 低温 氨 锰基催化剂

The study on selective catalytic reduction of NO_x by ammonia by Mn/TiO₂-based catalyst

Abstract

NH₃-SCR(Selective Catalytic Reduction of NO_x by ammonia)is a kind of effective De-NO_x technology, and now, the key point of the study is how to realize the De-NO_x at a low temperature. This task uses Mn as active component, use TiO₂ as the isotopic carrier and study the screening of methods of the preparation and the kinds of the promoter to study the catalyst, which has a high efficiency in wiping off NO_x at a low temperature. At the same time, this task also conducts the activity rating test and NH₃-TPD surface features test.

At the first section, the catalyst is prepared by the sol-gel method, the coprecipitation method and the hydrothermal synthesis method. The catalyst made by the sol-gel method has the best result in wiping off NO_x, its efficiency of wiping off NOx is 99% at 200 centigrade. In view of the results of NH₃-TPD surface features test, the catalyst made by the sol-gel method has the highest temperature of the peak at the low temperature desorption and the high temperature desorption, which means the surface acid site of this catalyst is the strongest. And the catalyst made by the sol-gel method has the biggest area of the desorption peak, which means this catalyst has the most acid content. Thus it can be seen, the catalyst made by the sol-gel method has the best catalytic activity.

At the second section, Ce, Cu and Fe is added into the catalyst respectively, which is prepared by the sol-gel method. This is aim to study the influence of these promoter. The catalyst which is added with Fe has the longest temperature window. Its efficiency of wiping off NO_x has reached 99% at 160 centigrade, until 300 centigrade, the efficiency of wiping off NO_x just begins to drop. Its length of the temperatur window is longer than other catalyst. In view of the results of NH₃-TPD surface features test, the catalyst which is added with Fe has the highest temperature of the peak at the low temperature desorption and the high temperature desorption, which means the surface acid site of this catalyst is the strongest. And the catalyst which is added with Fe has the biggest area of the desorption peak, which means this catalyst has the most acid content. Thus it can be seen, the catalyst which is added with Fe has the best catalytic activity.

Key Words:NO_x; SCR; low temperature; NH₃; Mn-based catalyst

目 录

摘要 I

Abstract II

目 录 I

第一章 绪论 1

1.1 引言 1

1.2 氮氧化物产生的控制 2

1.2.1 氮氧化物燃烧前处理技术 2

1.2.2 氮氧化物燃烧控制技术 2

1.3 氮氧化物治理技术 2

1.3.1 选择性非催化还原法 3

1.3.2 选择性催化还原（SCR） 3

1.4 Mn/TiO₂的研究 4

1.4.1 Mn-Cu/TiO₂复合氧化物 6

1.4.2 Mn-Ce/TiO₂复合氧化物 6

1.4.3 Mn-Fe/TiO₂复合氧化物 7

1.5 选题的目的、意义和研究的主要内容 7

第二章 实验部分 9

2.1 实验原料、试剂与仪器 9

2.1.1 实验原料与化学试剂 9

2.1.2 主要实验仪器 9

2.2 催化剂的表征方法 10

2.2.1 程序升温脱附（NH₃-TPD)测试 10

2.3 催化剂活性评价装置及方法 10

2.3.1 催化剂还原NO_x性能测试 10

2.4 不同制备方法对催化活性的影响 11

2.4.1 催化剂制备 11

2.4.2 催化剂的活性评价 12

2.4.3 NH₃-TPD表征分析 13

2.5 助催化剂对催化活性的影响 14

2.5.1 催化剂的制备 14

2.5.2 催化剂的活性评价 15

2.5.3 NH₃-TPD表征分析 15

第三章 总结与展望 17

3.1 结论 17

3.2 后续工作建议与展望 17

参考文献 18

致谢 21

第一章 绪论

1.1 引言

NO_x是大气染的主要污物之一，其主要成分是NO₂和NO，还有少量的N₂O₅，N₂O₃，NO₃，N₂O₄等。NO_x的来源主要分为自然源和人为源，一方面是由自然界中的火山活动、雷电、微生物降解蛋白质产生的，每年约生成5亿吨；还有一方面主要来自火力发电厂、工业锅炉、硝酸厂和机动车尾气的排放，每年约产生5千万吨。在认为排放源的NO_x中，46%来自电厂排放，49%来自机动车排放。随着机动车数量的增加和能源消耗的增大，氢氧化物的排放量也不断地增加，加上人为排放的NO_x的浓度高，排放集中的特点，其引起的区域危害性更大。

NO_x的排放会严重危害人类的生产活动和自然生态环境，包括对人体健康的危害，对植物的危害，造成光化学烟雾，形成酸雨，造成臭氧层的破坏。NO_x本身具有一定的毒性，当NO_x在空气中的含量在20-50ppm时，会对人的眼睛产生一定的刺激作用；当NO_x的含量超过150ppm时，会对人的呼吸系统产生强烈的刺激，进一步引发呼吸窘迫、胸闷、肺水肿等症状，更严重的甚至危及生命。高层大气中的NO_x也会与大气中的水、空气等物质发生反应，形成酸雨，酸雨会腐蚀建筑、文物等，也会造成土壤酸化，影响农业生产，引起水体污染和生物死亡等。

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