Experimental study on selective catalytic reduction of NO by C3H6 over Fe-Ag/Al2O3 catalysts
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摘要: 以蜂窝状陶瓷为载体,采用溶胶凝胶法和浸渍法制备了不同Fe/Ag负载量的Fe-Ag/Al2O3催化剂。以C3H6为还原剂,在模拟烟气条件下和200-700 ℃范围内,程序控温的陶瓷管流动反应器上进行了催化还原NO的性能评估。结果表明,7.2Fe/1.9Ag/20Al2O3/CM在500和550 ℃时催化C3H6还原NO的脱硝效率分别超过90%和达到100%。铁离子能有效地提高Ag/20Al2O3/CM催化剂抵抗烟气中的SO2和H2O的能力。结果表明,当烟气中含有体积分数为0.02%的SO2和8%的H2O时,在500 ℃时7.2Fe/1.9Ag/20Al2O3/CM催化C3H6还原NO的脱硝效率不受影响,在6 h的连续实验中保持90%的脱硝效率而没有下降。而未经铁离子修饰的2Ag/20Al2O3/CM的催化活性则受烟气中的SO2和H2O影响很大,0.02%的SO2和8%的H2O分别使2Ag/20Al2O3/CM在500 ℃时催化C3H6还原NO的脱硝效率迅速从70%分别下降至46%和25%。XRD和SEM表征结果表明,经铁离子修饰后的7.2Fe/1.9Ag/20Al2O3/CM催化剂中,形成了AgFeO2以及Fe3+,催化剂表面变得疏松多孔,形成以Fe3O4为主的针状和片状晶体。H2-TPR结果表明,7.2Fe/1.9Ag/20Al2O3/CM比Ag/20Al2O3/CM在更宽的温度范围内具有更好的还原特性。吡啶吸附红外光谱(Py-FTIR)实验结果显示,Fe增加了催化剂表面的Lewis酸性位。
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关键词:
- 选择性催化脱硝 /
- 丙烯 /
- Fe-Ag/Al2O3催化剂
Abstract: Sol-gel and impregnation methods were used to prepare the Fe/Ag/Al2O3 catalysts supported on the monolithic cordierite with different Fe/Ag loading ratios. The catalytic performance to reduce NO with C3H6 was evaluated in a one-dimensional electrically heated temperature programmed ceramic tubular reactor in simulated flue gas atmosphere at 200-700 ℃. The results show that the NO reduction efficiency on 7.2Fe/1.9Ag/20Al2O3/CM with C3H6 is more than 90% and reaches about 100% at the temperatures of 500 ℃ and 550 ℃ respectively. Iron can effectively improve the ability of Ag/20Al2O3/CM catalysts to resist SO2 and H2O in flue gas. When SO2 and H2O are 0.02% and 8% in the flue gas, the NO reduction efficiency is almost not influenced on 7.2Fe/1.9Ag/20Al2O3/CM at 500 ℃. The 90% NO reduction efficiency is maintained during 6 h without decrease. However, the catalytic activity of 2Ag/20Al2O3/CM without iron modification is strongly influenced by SO2 and H2O in the flue gas. The NO reduction efficiency on Ag/20Al2O3/CM decreases rapidly from about 70% to 46% and 25% respectively, when the SO2 and H2O are 0.02% and 8% in the flue gas. The results of XRD and SEM of the catalyst show that AgFeO2 and Fe3+ are formed in the 7.2Fe/1.9Ag/20Al2O3/CM catalyst after the modification by iron, and the surface of the catalyst become loose and porous, forming Fe3O4-based needle-like and flaky crystals. H2-TPR results show that 7.2Fe/1.9Ag/20Al2O3/CM has better reduction properties than Ag/20Al2O3/CM in the wider temperature range. Pyridine adsorption Infrared Spectroscopy (Py-FTIR) experimental results show that Fe increases the Lewis acid sites in the catalyst surface.-
Key words:
- selective catalytic reduction of NO /
- C3H6 /
- Fe-Ag/Al2O3 catalyst
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图 4 不同温度时SO2和H2O对7.2Fe/1.9Ag/20Al2O3/CM和2Ag/20Al2O3/CM催化C3H6还原NO的影响
Figure 4 Effect of SO2 and H2O on C3H6-SCR of NO by 7.2Fe/1.9Ag/20Al2O3/CM(a) and 2Ag/20Al2O3/CM(b) at different temperature
—○—: 7.2Fe/1.9Ag/20Al2O3/CM, with SO2 and H2O; —●—: 7.2Fe/1.9Ag/20Al2O3/CM, without SO2 and H2O; --■--: 2Ag/20Al2O3/CM, without SO2 and H2O; --□--: 2Ag/20Al2O3/CM, with SO2 and H2O;
表 1 不同负载量样品的微孔隙特性
Table 1 Textural properties of different Fe/Ag loading on Al2O3
Catalyst ABET/ (m2·g-1) νp/ (cm3·g-1) dp/ nm 20Al2O3/CM[16] 27 0.076 4.4 2Ag/20Al2O3/CM 9 0.042 17.7 7.2Fe/1.9Ag/20Al2O3/CM 23 0.054 9.23 5.5Fe/20Al2O3/CM 19 0.039 6.54 表 2 三组样品中酸性位的含量
Table 2 Acid content of different Fe/Ag loading on Al2O3
Sample 150 ℃ 300 ℃ B /(mmol·g-1) L /(mmol·g-1) B /(mmol·g-1) L /(mmol·g-1) 20Al2O3/CM 0 0.001 20 0 0.000 60 2Ag/20Al2O3/CM 0 0.001 58 0 0.000 63 7.2Fe/1.9Ag/20Al2O3/CM 0 0.002 33 0 0.001 33 -
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