碱金属中毒对Mn-Ce催化剂NH3-SCR反应影响探究
关键词 NH3-SCR MnOx-CeO2催化剂 钾中毒 稳态动力学
毕业论文设计说明书外文摘要
Title Effect of Potassium Poisoning of a Mn-Ce Catalyst for the Selective Catalytic Reduction of NOx with NH3
Abstract
The effect of potassium poisoning of a MnOx-CeO2 catalyst for the selective catalytic reduction of NOx with NH3 (NH3-SCR) was investigated in this work. The experimental results showed that the SCR performance over MnOx-CeO2 catalyst decreased after the catalyst poisoned by potassium. And then the reaction mechanism was studied using temperature programmed desorption (TPD), transient reaction, in situ diffuse reflectance infrared Fourier transform spectra (in situ DRIFTS), steady-state kinetic study and so on. The TPD result indicated that the adsorption activities of NH3 and NO over MnOx-CeO2 catalyst were restrained due to potassium poisoning. The in situ DRIFTS and transient reaction results further suggested that the adsorption quantity of NH3 on catalyst surface decreased and the nitrate species adsorbed on catalyst surface changed after the potassium deposited on MnOx-CeO2 catalyst. Therefore, the formation of N2O through Eley-Rideal mechanism was restrained and the formation of N2O through Langmuir-Hinshelwood mechanism was promoted. In addition, the steady-state kinetic study indicated that the rate of NO reduction through Langmuir-Hinshelwood mechanism and Eley-Rideal mechanism decreased, the NSCR reaction was restrained and the C-O reaction was promoted in the meantime after the MnOx-CeO2 catalyst poisoned by potassium.
Keywords NH3-SCR MnOx-CeO2 catalyst potassium poisoning steady-state reaction kinetic
目 次
1 引言 1
1.1 氮氧化物的来源及危害 1
1.2 烟气脱硝技术 1
1.3 研究意义及主要内容 4
2 实验部分 6
2.1 实验仪器与试剂 6
2.2 催化剂的制备 6
2.3 催化剂活性评价 7
2.4 催化剂表征 8
2.5 原位红外和瞬态反应 8
2.6 反应动力学 8
3 实验结果 10
3.1 催化剂活性评价 10
3.2 催化剂表征 10
3.3 原位红外与瞬态反应 14
3.4 稳态动力学 18
4 结果讨论 21
4.1 反应机理 21
4.2 动力学研究 22
4.3 模型验证 24
结 论 26
致 谢 27
参考文献28
1 引言
1.1 氮氧化物的来源及危害
氮氧化物（NOx）主要有NO、NO2、N2O、N2O3、N2O4和N2O5，其来源主要分为自然污染源和人为污染源，其中来自自然环境中的闪电、微生物作用等自然污染源的NOx生成量约为每年5×108 t，来自生产活动、机动车排气等人为污染源的NOx生成量约为每年5×107 t[1]。人为产生的NOx大部分来自燃料高温燃烧（90%以上），其次是来自化工生产中的有关过程，如硝酸生产、金属表面硝酸处理和硝化过程等。燃料燃烧产生的NOx分为燃料型、热力型和瞬时型[2]。因燃烧产生的NOx中NO占95%以上，其余主要是NO2。在大气环境中NO经过反应最终转化为NO2，因此NOx主要以NO、NO2的形式存在于大气中。