Abstract:

A series of Fe _x MnCe₁-AC catalysts were prepared by ultrasonic-assisted impregnation method with activated carbon as carrier. The low-temperature NH₃-SCR denitrification activity of the catalysts was investigated, and the best activity catalyst was established. The effect of SO₂ on its denitration performance was also explored. The results showed that Fe_0.1MnCe₁-AC catalyst exhibited best denitration efficiency at low-temperature among prepared catalysts, the conversion rate of NO exceeded 90% with the temperature range from 120℃ to 220℃ (no SO₂). In addition, the catalyst could maintain NO conversion rate of approximately 77% under the atmosphere of 180℃ and SO₂ concentration of 429 mg/m³. The mechanism of SO₂ poisoning on the catalyst was characterized with BET, XRD, XPS, H₂-TPR NH₃-TPD, FT-IR and TGA. It was observed that SO₂ could form ammonium sulfate ( (NH₄)₂SO₄, (NH₄)₂SO₃ ), and MnSO₄ with NH₃ and the metal components in the catalyst, which changed the pore structure of the fresh catalyst and reduced the Br?nsted acid sites and Lewis acid sites on the catalyst surface. These variation made the inhibitory effect on the catalytic adsorption capacity of NH₃. Moreover, SO₂ also promoted a decrease in the number of Mn⁴⁺, Ce³⁺, Fe³⁺ and Fe³⁺—OH^- groups in the catalyst, and lessened the surface reducible species, thereby reducing the activity of the catalyst denitration.

Key words: selective catalytic reduction, activated carbon, catalyst, nitric oxide, sulfur dioxide, poisoning mechanism

摘要：

以活性炭为载体，通过超声辅助浸渍法制备了一系列Fe _x MnCe₁-AC催化剂，考察了该系列催化剂的低温NH₃-SCR脱硝活性，确立了活性最佳的催化剂，并探究了SO₂对其脱硝性能的影响。结果表明，Fe_0.1MnCe₁-AC催化剂低温脱硝活性最高，在120~220℃范围内NO的转化率均在90%以上（无SO₂）。此外，在180℃、SO₂浓度为429 mg/m³时，该催化剂仍能保持77%左右的脱硝率。通过BET、XRD、XPS、H₂-TPR、NH₃-TPD、FT-IR、TGA等表征手段对催化剂的SO₂中毒机理进行了分析。研究发现，SO₂能与NH₃及催化剂中金属组分生成硫酸铵盐((NH₄)₂SO₄、(NH₄)₂SO₃)、MnSO₄等物质，改变了原催化剂孔道结构并减少了催化剂表面Br?nsted和Lewis酸性位点，抑制了催化剂吸附NH₃的能力。更多地，SO₂促使催化剂中Mn⁴⁺、Ce³⁺、Fe³⁺和Fe³⁺—OH^-基团数量下降，表面可还原物质减少，从而降低了催化剂的脱硝活性。

关键词: 选择性催化还原, 活性炭, 催化剂, 氮氧化物, 二氧化硫, 中毒机理