摘要本文探究了SO2对CeO2/TiO2催化剂NH3-SCR活性的影响机制。CeO2/TiO2催化剂在SO2气氛中的活性和硫化后CeO2/TiO2催化剂的活性类似，表明SO2对CeO2/TiO2催化剂SCR活性的影响与硫化作用密切相关。原位红外和TPD实验的结果表明，硫化为催化剂表面提供了酸性位，大幅提升了催化剂的氨吸附能力，而反应物氧化的结果显示，硫化后催化剂的氧化还原能力受到抑制。本文通过建立反应动力学模型，观察模拟SCR反应及C-O反应（氨的催化氧化）速率常数的变化，发现硫化后会抑制C-O反应，这与硫化抑制了催化剂的氧化还原能力有关。同时发现，硫化在低温时会抑制E-R与L-H两种途径的SCR反应，高温时（400 ~ 500 oC）促进两种途径的SCR反应。这是因为硫化后催化剂表面上NH3的吸附位与氧化位分离，降低了NH3的活化几率，抑制了SCR反应；高温时促进了催化剂的氧化还原能力，同时催化剂对NH3的吸附能力增强，促进了SCR反应。26963
关键词 Eley-Rideal机理 Langmuir-Hinshelwood机理 硫酸盐化作用 氨的催化氧化 反应 动力学模型
毕业论文设计说明书外文摘要
Title Effect of SO2 on the CeO2/TiO2 Catalyst in the Selective
Catalytic Reduction of NO by NH3
Abstract
In this work, the mechanism of the effect of SO2 on the SCR reaction over CeO2/TiO2 was studided. CeO2/TiO2 showed a similar SCR activity in the presence of SO2 compared with sulfated CeO2/TiO2, which indicated that the effect of SO2 on the SCR reaction over CeO2/TiO2 was mainly due to the sulfation of SO2. The results of DRIFT and TPD demonstrated that the adsorption of NH3 on CeO2/TiO2 was obviously promoted after the sulfation for the induction of SO42-. The established reaction kinetics model showed that the rate of SCR reaction and C-O reaction changed greatly, which was related to the drops of the redox ability of the catalyst after sulfation. Meanwhile, the SCR activity was inhibited at low temperature, while promoted at high temperature. This is because the adsorption sites for NH3 adsorption and the oxidization agents for NH3 oxidization on CeO2/TiO2 were separated after the sulfation, leading an obvious repression of the oxidization of NH3 to NH2. While the redox ability of the catalyst after sulfation was promoted at high temperature, and sulfated CeO2/TiO2 had stronger adsorption capacity for NH3, as a result, the SCR activity of sulfated CeO2/TiO2 was better than that over CeO2/TiO2.
Keywords Eley-Rideal mechanism Langmuir-Hinshelwood mechanism Sulfation C-O reaction the kinetic model
目 次
1 引言 1
1.1 氮氧化物的组成及来源 1
1.2 氮氧化物的危害 1
1.3 氮氧化物的控制技术 1
1.4 课题的提出与内容 2
2 实验部分 4
2.1 实验仪器、试剂与气体 4
2.2 CeO2/TiO2催化剂的制备与硫化 5
2.3 催化剂活性评价 5
2.4 原位红外表征 7
2.5 TPD实验 7
3 结果与讨论 8
3.1 活性评价 8
3.2 TPD实验 8
3.3 反应物氧化 10
3.4 原位红外 11
3.5 稳态动力学研究 16
结 论 23
致 谢 24
参考文献 25
1 引言
1.1 氮氧化物的组成及来源
近年来，大气污染问题变得愈来愈突出，而氮氧化物（NOx）作为大气中的主要污染物引起人们广泛关注。NOx主要包括：N2O、NO、N2O3、NO2、N2O4和N2O5。大气中氮氧化物的主要来自两个方面：一方面为自然界固氮菌、雷电等过程；另一方面为人类活动，其中90%以上为燃料燃烧产生。燃烧过程生成的氮氧化物又分为：燃料中固定氮氧化而成的燃料型氮氧化物、高温时产成的热力型氮氧化物、低温下由于含碳自由基的存在而产生的瞬时一氧化氮[1, 2]。 SO2对CeO2TiO2催化剂NH3-SCR反应影响探究:http://www.youerw.com/huaxue/lunwen_21286.html