Study on the activity and mechanism of selective catalytic reduction of NO with NH3 over MnαTi1-α catalyst at medium-low temperatures
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摘要: 采用浸渍法制备了不同MnOx负载量的SCR催化剂，检测其在中低温下的脱硝活性和抗SO2中毒性能，并分析影响MnαTi1-α催化剂中低温活性的机理。采用BET、XRD、XPS、NH3-TPD和H2-TPR对催化剂表征。研究表明，随着MnOx负载量的增加，MnαTi1-α催化剂最高脱硝活性温度区间向低温区移动，Mn0.1Ti0.9催化剂在200-385 ℃脱硝效率达80%以上。SO2会造成MnαTi1-α催化剂脱硝活性显著下降，且不可逆。当MnOx负载量增加时，催化剂比表面积先增大后略微减小、H2-TPR中Mn4+峰面积增大、表面化学吸附氧增加，有利于NH3-SCR反应在低温下的进行。MnαTi1-α催化剂的酸性位点随MnOx含量增加而增多，H2还原峰出现温度较低，表明MnαTi1-α催化剂具有良好的中低温氧化还原性。Abstract: MnαTi1-α catalysts for selective catalytic reduction (SCR) of NO were prepared with impregnation method and their denitration activity and SO2 resistance at medium-low temperature were evaluated. The catalysts were characterized using BET, XRD, XPS, NH3-TPD and H2-TPR. The results showed that the temperature range of the highest denitration activity of MnαTi1-α catalyst shifted to the lower temperature zone along with the increase of MnOx loading. The denitration efficiency of Mn0.1Ti0.9 catalyst reached over 80% at 200-385 ℃. SO2 could bring down denitration activity of MnαTi1-α catalyst greatly and resulted in irreversible deactivation. The specific surface area of the catalyst first increased then slightly decreased with the increase of Mnx loading. Both Mn4+ peak area in H2-TPR and surface chemical adsorbed oxygen increased along with the increase of MnOx loading. All these factors were beneficial to the proceeding of NH3-SCR reaction at low temperature. With the increase of MnOx loading, the acid sites of MnαTi1-α catalyst increased and the reduction peak at low temperature appeared, indicating that MnαTi1-α catalyst had good redox performance at medium and low temperature.
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Key words:
- selective catalytic reduction /
- MnOx /
- medium-low temperature SCR /
- NH3 reduction /
- SO2 resistance
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图 1 MnαTi1-α催化剂脱硝活性及N2选择性评价系统示意图
Figure 1 Experimental setup for denitration activity test and N2 selectivity evaluation of the MnαTi1-α catalysts
图 2 MnOx负载量对MnαTi1-α催化剂脱硝活性的影响
Figure 2 Influence of MnOx loading on the denitration activity of the MnαTi1-α catalysts
(NO=500 μL/L, NH3=500 μL/L, O2=3%, balance N2, GHSV=3.6×104 h-1)
图 3 MnOx负载量对MnαTi1-α催化剂N2选择性的影响
Figure 3 Influence of MnOx loading on N2 selectivity of the MnαTi1-α catalysts
(NO=500 μL/L, NH3=500 μL/L, O2=3%, balance N2, GHSV=3.6×104 h-1)
图 4 烟气中SO2对MnαTi1-α催化剂脱硝活性的影响
Figure 4 Influence of SO2 on denitration activity of the MnαTi1-α catalysts
(NO=500 μL/L, NH3=500 μL/L, SO2=300 μL/L, O2=3%, balance N2, GHSV=3.6×104 h-1)
图 5 MnαTi1-α催化剂氮吸附-脱附曲线和孔径分布
Figure 5 N2 absorption-desorption isotherms and pore size distribution curves of the MnαTi1-α catalysts
(a): Mn0.1Ti0.9; (b): Mn0.07Ti0.93; (c): Mn0.05Ti0.95; (d): Mn0.03Ti0.97; (e): Mn0.01Ti0.99; (f): Mn0.005Ti0.995
表 1 MnαTi1-α催化剂孔隙结构特征参数
Table 1 Pore structure parameters of the MnαTi1-α catalyst
Catalyst Specific surface area A/(m2·g-1) Pore volume v/(cm3·g-1) Average pore diameter d/nm Mn0.1Ti0.9 55.4 0.4482 33.6 Mn0.07Ti0.93 57.0 0.4975 34.9 Mn0.05Ti0.95 51.5 0.4648 35.5 Mn0.03Ti0.97 50.9 0.4023 31.6 Mn0.01Ti0.99 52.5 0.3934 30.0 Mn0.005Ti0.995 49.8 0.3533 28.4 
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表 2 MnαTi1-α催化剂的表面元素含量
Table 2 Surface element contents of the MnαTi1-α catalysts
Catalyst Content w/% Mn3+ Mn4+ Oα Oβ Mn0.1Ti0.9 31.2 68.8 35.0 65.0 Mn0.05Ti0.95 35.6 64.4 29.4 70.6 Mn0.01Ti0.99 40.8 59.2 28.2 71.8
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表 3 MnαTi1-α催化剂NH3-TPD分峰数据
Table 3 NH3-TPD peak parameters of the MnαTi1-α catalysts
Catalyst Peak position t/℃ peak1 peak2 peak3 peak4 peak5 peak6 Mn0.1Ti0.9 224.13 285.46 351.64 448.91 553.32 - Mn0.05Ti0.95 192.05 244.62 296.31 346.37 425.92 495.47 Mn0.01Ti0.99 196.43 244.04 305.02 362.75 443.37 - peak area peak1 peak2 peak3 peak4 peak5 peak6 Mn0.1Ti0.9 259.43 143.73 245.12 366.88 13.58 - Mn0.05Ti0.95 131.73 289.42 84.86 244.68 242.42 41.88 Mn0.01Ti0.99 86.67 156.50 158.38 106.03 124.68 -
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