Sulfur-poisoning and thermal reduction regeneration of holmium-modified Fe-Mn/TiO2 catalyst for low-temperature SCR
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摘要: 以Ho改性Fe-Mn/TiO2低温SCR脱硝催化剂为研究对象,通过活性评价和一系列表征技术对其低温抗硫性能和催化剂的热还原再生进行研究。结果表明,硫酸铵((NH4)2SO4)在催化剂表面的沉积以及活性组分硫酸化(MnSO4)是催化剂硫中毒的主要原因。当烟气中的SO2体积分数低于0.04%时,Fe0.3Ho0.1Mn0.4/TiO2催化剂呈现出良好的抗硫性。在此条件下,当切断SO2的供应时催化剂的脱硝活性可获得显著恢复。当通入的SO2体积分数增加至0.1%时,催化剂会发生不可逆失活。在体积分数5% NH3气氛下,失活催化剂经过350 ℃的热还原再生处理60 min后,其微观结构和理化性质能够得到明显恢复,且NOx转化率可以回升至80%左右。Abstract: The effect of SO2 on the low-temperature SCR activity and the thermal reduction regeneration for holmium-modified Fe-Mn/TiO2 catalyst were investigated by activity assessment and various characterization methods. The deposition of ammonium sulfate ((NH4)2SO4) on catalyst surface and the sulfuration of active component (MnSO4) were proved to be the main causes for the deactivation in the presence of SO2. The catalyst Fe0.3Ho0.1Mn0.4/TiO2 exhibited superior SO2 durability when the concentration of SO2 was lower than 0.04%, and the catalytic activity could markedly recover with the termination of sulfur-poisoning source. The deactivation behavior was irreversible when the concentration of SO2 was increased to 0.1% but the poisoned catalyst could be regenerated after thermal reduction (350 ℃) for 60 min by 5% NH3. The microstructure and physicochemical properties could be significantly restored after the thermal reduction regeneration. Moreover, the NOx conversion could return to about 80%.
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Key words:
- SCR /
- denitration /
- low-temperature /
- thermal reduction regeneration /
- (NH4)2SO4
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图 9 Fe0.3Ho0.1Mn0.4/TiO2催化剂再生前后的in situ DRIFTS谱图
Figure 9 in situ DRIFTS spectra of fresh, deactivated and regenerated catalysts
(a): fresh Fe0.3Ho0.1Mn0.4/TiO2; (b): deactivated Fe0.3Ho0.1Mn0.4/TiO2; (c): regenerated Fe0.3Ho0.1Mn0.4/TiO2 a: 40 ℃; b: 60 ℃; c: 80 ℃; d: 100 ℃; e: 120 ℃; f: 140 ℃; j: 160 ℃; h: 180 ℃; i: 200 ℃; g: 220 ℃
表 1 Fe0.3Ho0.1Mn0.4/TiO2催化剂再生前后的BET比表面积和孔容孔径
Table 1 BET surface areas and pore parameters of fresh, deactivated and regenerated catalysts
Catalyst ABET /(m2·g-1) Total pore volume v/(cm3·g-1) Average pore width d/nm Fresh Fe0.3Ho0.1Mn0.4/TiO2 95 0.28 11.99 Deactivated Fe0.3Ho0.1Mn0.4/TiO2 5 0.23 174.34 Regenerated Fe0.3Ho0.1Mn0.4/TiO2 49 0.41 33.11 表 2 Fe0.3Ho0.1Mn0.4/TiO2催化剂再生前后的XRF表征
Table 2 XRF results of fresh, deactivated and regenerated catalysts
Sample Element content w/% Ti Mn Ho Fe S N Fresh Fe0.3Ho0.1Mn0.4/TiO2 24.10 13.64 9.86 9.77 0.12 0.00 Deactivated Fe0.3Ho0.1Mn0.4/TiO2 17.46 9.50 6.94 7.05 9.76 8.81 Regenerated Fe0.3Ho0.1Mn0.4/TiO2 23.41 13.16 9.26 9.40 0.80 0.00 表 3 Fe0.3Ho0.1Mn0.4/TiO2催化剂再生前后的H2-TPR图谱分析
Table 3 H2-TPR analysis results of fresh, deactivated and regenerated catalysts
Sample Reduction peak area Peak area ratio H2/Mn(mol ratio) Ⅰ Ⅱ Ⅲ total Ⅰ/Ⅱ Ⅱ/Ⅲ Ⅰ Ⅱ Ⅲ total Fresh Fe0.3Ho0.1Mn0.4/TiO2 1 973 1 795 995 4 763 1.10 1.80 0.94 0.86 0.48 2.28 Deactivated Fe0.3Ho0.1Mn0.4/TiO2 944 1 653 216 2 813 0.57 7.65 0.45 0.79 0.10 1.34 Regenerated Fe0.3Ho0.1Mn0.4/TiO2 1 990 1 832 528 4 350 1.08 3.47 0.95 0.88 0.25 2.08 表 4 Fe0.3Ho0.1Mn0.4/TiO2催化剂再生前后的NH3-TPD图谱分析
Table 4 NH3-TPD analysis results of fresh, deactivated and regenerated catalysts
Sample NH3 desorption peak area weak acid
( < 300 ℃)dium-strong acid
(300-500 ℃)strong acid
( > 500 ℃)total Fresh Fe0.3Ho0.1Mn0.4/TiO2 6 621 6 539 6 126 19 286 Deactivated Fe0.3Ho0.1Mn0.4/TiO2 2 741 2 973 2 433 8 147 Regenerated Fe0.3Ho0.1Mn0.4/TiO2 7 795 4 402 4 062 16 259 -
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