论文总字数：29800字

摘 要

NH₃-SCR脱硝技术因脱硝效率高、选择性好、技术成熟等优点而广泛应用于工业锅炉、火力发电厂等行业。当前商业V₂O₅-WO₃(MoO₃)/TiO₂催化剂在工业脱硝中得到广泛的使用（尤其是火电市场），但该催化剂的操作温度窗口窄（300~450°C），在250°C以下的低温活性不足，且钒容易造成二次化学污染等缺点。

以天然气为燃料的工业锅炉、炉窑、内燃机、发电机组等设备的烟气排放通常具有出口温度低（180~250°C），灰分以及硫含量低，氮氧化物排放要求高等特点。这也就使得商用钒基催化剂在这类方面的应用受到了限制，因此需要开发一种在低温下具有高催化活性的新型脱硝催化剂。低温SCR催化剂主要包括贵金属催化剂、沸石分子筛型和以Mn、Ce、Zr等氧化物为活性组分的金属氧化物类。

在本研究中，对锰、铈、锆三种元素制备的低温脱硝催化剂进行了探索研究，通过对比单/双/三组元催化剂的脱硝活性发现，三组元的50Mn-25Ce-25Zr脱硝催化剂显示了最优的低温脱硝活性，而其中Mn、Ce、Zr三组元的添加被确认均为必要成份。通过进一步借助BET、XRD、XPS、NH₃-TPD等表征手段对催化剂理化性质进行分析发现，锰铈锆三组元之间的强相互作用导致的催化剂表面Mn⁴ 含量升高，而Mn⁴ 比例的上升引起了催化剂表面化学吸附氧含量O_α的提高，这是导致三组元催化剂具有较优催化活性的主要原因之一。此外，锰铈锆三组元之间强相互作用提高了比表面积以及表面Lewis酸位点是促使三组元催化剂具有较优催化活性的另一个主要原因。

关键词：锰基催化剂 NH₃-SCR 氧化铈 低温脱硝 水热合成法

Mn-Ce-Zr catalyst for NH₃-SCR denitration at low temperatures

Abstract

Selective catalytic reduction of NO with NH₃ is widely used in industrial boilers, thermal power plants and other industries due to its advantages such as high denitration efficiency, high selectivity and mature technology. Currently, the commercial V₂O₅-WO₃(MoO₃)/TiO₂ catalyst is widely used in industrial denitrification (especially in thermal power market), but the catalyst has a narrow operating temperature window (300~450℃) and low temperature activity below 250℃. In addition, vanadium can cause secondary chemical pollution .

The flue gas emission of industrial boilers, kilns, internal combustion engines, generator sets and other equipment that uses natural gas as fuel usually has low outlet temperature (180~250℃), low ash and sulfur content, and high nitrogen oxide emission requirements. These have limited the application of commercial vanadium- based catalysts , so it is necessary to develop a new type of denitration catalyst with high catalytic activity at low temperatures. Low-temperature SCR catalysts mainly include precious metal catalysts, zeolite molecular sieve types, and metal oxides with Mn, Ce, Zr and other oxides as active components.

In this study, the low-temperature denitration catalysts prepared by the manganese, cerium and zirconium were explored. By comparing the denitration activity of unitary/binary/ternary catalysts, it was found that 50Mn-25Ce-25Zr denitration catalyst showed the optimal low-temperature denitration activity , and the addition of Mn, Ce, and Zr components is confirmed to be essential components. Through further analysis of the physical and chemical properties of the catalyst by means of BET, XRD, XPS, NH₃-TPD and other characterization methods, it was found that the strong interaction between the three components of manganese, cerium,and zirconium caused the increase of Mn⁴ content on the catalyst surface, and the increase in the proportion of Mn⁴ caused the increase of the surface chemically adsorbed oxygen content , which is one of the main reasons leading to the superior catalytic activity of the three-component catalyst. In addition, the strong interaction between the three components of manganese, cerium and zirconium improves specific surface area and surface Lewis acid sites, which is another main reason for the three-component catalyst to have better catalytic activity.

Key Words: Mn based catalyst; NH₃-SCR; cerium oxide; Low-temperature

denitrification; hydro-thermal method

目 录

摘 要 I

Abstract i

第一章 文献综述 1

1.1研究背景 1

1.2脱硝处理技术 1

1.2.1 燃烧前控制 1

1.2.2 燃烧过程控制 2

1.2.3烟气后处理技术 2

1.3脱硝催化剂研究进展 2

1.3.1低温SCR脱硝催化剂 2

1.3.2低温SCR脱硝反应影响因素 4

1.4 研究内容及意义 5

第二章 实验部分 6

2.1主要试剂和实验仪器 6

2.1.1 实验试剂 6

2.1.2主要实验仪器 6

2.2 催化活性评价系统 7

2.2.1 催化活性评价系统简介 7

2.2.2 活性测试条件 8

2.3催化剂表征方法 9

第三章 锰铈锆低温脱硝催化剂的构效解析 10

3.1 前言 10

3.2 锰铈锆催化剂的制备 11

3.3 单/双/三组元锰铈锆催化剂的比较 11

3.3.1 单/双/三组元锰铈锆催化剂的脱硝活性 11

3.3.2 织构特征分析 12

3.3.3 XRD分析 13

3.3.4 XPS分析 15

3.3.5 NH₃-TPD分析 21

第四章 结论与展望 23

4.1 结论 23

4.2 展望 23

参考文献 24

致 谢 28

文献综述

1.1研究背景

近年来，我国社会经济稳步发展，但在这背后是人们对化石能源需求的日渐提高，以及大气污染问题的日益严重。其中，氮氧化物（NO_X）是主要的大气污染物之一。NO_X排放是由固定或移动来源产生的，例如燃气电厂是常见的固定源，汽车发动机是常见的移动源。氮氧化物主要包括NO、NO₂和N₂O、NO₃等。这些氮氧化物的危害主要体现为^[1]：1）对人和动物的毒害性；2）易形成酸雨、酸雾；3）形成光化学烟雾；4）对臭氧层的破坏以及造成温室效应等。因此我国出台了一系列相关的政策、技术准则及标准法规等，对氮氧化物以及其他大气污染物的排放及治理进行指导和约束。

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