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摘要本文研究了以Mn-Fe尖晶石为催化剂的低温NH3-SCR反应中副产物N2O的形成机理，证明反应中N2O选择性与反应物的浓度和反应空速有关。原红外光谱和瞬态反应研究显示Eley-Rideal机理与Langmuir-Hinshelwood机理都会导致N2O的生成，但Langmuir-Hinshelwood机理生成N2O的选择性要低于Eley-Rideal机理。随着反应空速的降低，经Langmuir-Hinshelwood机理还原的NO的比例明显增大，因此Mn-Fe尖晶石NH3-SCR反应的N2O选择性随着空速的降低而减小。随着气态NO浓度的增加，催化剂表面的-NH2更多地被用来氧化气态NO，从而抑制了-NH的生成，使得Mn-Fe尖晶石NH3-SCR反应的N2O选择性减小。但随着气态NH3浓度的升高，由于NH3与NO + O2的竞争吸附作用，部分经Langmuir-Hinshelwood机理还原的NO会转变为经Eley-Rideal机理还原，因此Mn-Fe尖晶石NH3-SCR反应N2O选择性和NO转化率随着气态NH3浓度的升高而增大。21805
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关键词 N2O选择性 Eley-Rideal机理 Langmuir-Hinshelwood机理 空速
毕业论文设计说明书（论文）外文摘要
Title Effect of Mn doping on the Selective catalytic reduction of γ-Fe2O3
Abstract
The mechanism of N2O formation during the low temperature selective catalytic reduction (SCR) of NO with NH3 over Mn-Fe spinel was studied. N2O selectivity of NO reduction over Mn-Fe spinel was related to the reactant’s concentration and the gas hourly space velocity (GHSV) even in the presence of H2O. In situ DRIFTS study and the transient reaction study demonstrated that the Eley-Rideal mechanism and the Langmuir-Hinshelwood mechanism both contributed to N2O formation. However, N2O selectivity of NO reduction over Mn-Fe spinel through the Langmuir-Hinshelwood mechanism was much less than that through the Eley-Rideal mechanism. The ratio of NO reduction over Mn-Fe spinel through the Langmuir-Hinshelwood mechanism obviously increased with the decrease of GHSV. Therefore, N2O selectivity of NO reduction over Mn-Fe spinel decreased with the decrease of GHSV. Furthermore, more -NH2 on Mn-Fe spinel was used to reduce gaseous NO as gaseous NO concentration increased, resulting in an obvious restraint of the over-activation of adsorbed NH3. Therefore, N2O selectivity of NO reduction over Mn-Fe spinel obviously decreased with the increase of gaseous NO concentration. As gaseous NH3 concentration increased, NO reduction over Mn-Fe spinel through the Langmuir-Hinshelwood mechanism could transform to through the Eley-Rideal mechanism due to the adsorption competition of NH3 with NO+O2. Therefore, N2O selectivity of NO reduction over Mn-Fe spinel increased with the increase of gaseous NH3 concentration.
Keywords N2O selectivity the Langmuir-Hinshelwood mechanism the Eley-Rideal mechanism GHSV
目 次
1 绪论 1
1.1 引言 1
1.2 氮氧化物控制技术 1
1.3 研究意义及主要内容 5
2 实验部分 6
2.1 实验仪器与试剂 6
2.2 Mn-Fe尖晶石催化剂的制备 7
2.3 催化剂的活性评价 7
2.4 原位红外表征 10
3 实验结果 11
3.1 催化剂活性评价 11
3.2 瞬态反应与原位红外表征 14
3.3 稳态反应研究 17
4 结果讨论 20
4.1 构建动力学方程 20
4.2 气态NO浓度影响的机理探究 23
4.3 气态NH3浓度影响的机理探究 24
4.4 空速影响的机理探究 25
结 论 27