FexMnCe1-AC低温SCR催化剂SO2中毒机理研究

Mechanism study on SO2 poisoning of FexMnCe1-AC catalyst for low-temperature SCR

以活性炭为载体,通过超声辅助浸渍法制备了一系列FexMnCe1-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,Fe0.1MnCe1-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/m^3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Bronsted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Mn^4+、Ce^3+、Fe^3+和Fe^3+-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。

A series of FexMnCe1-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 Fe0.1MnCe1-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/m^3. 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 Mn^4+, Ce^3+, Fe^3+ and Fe^3+-OH^-groups in the catalyst, and lessened the surface reducible species, thereby reducing the activity of the catalyst denitration.