Mn/Ce-ZrO_2催化剂低温NH_3-SCR脱硝性能研究

Selective catalytic reduction of NO with NH_3 over Mn-based catalysts at low temperature

采用浸渍法制备了三种具有不同载体的锰基NH3低温选择性催化还原(NH3-SCR)催化剂Mn/Ce-ZrO2、Mn/P25和Mn/Al2O3。研究了三种催化剂低温SCR脱硝活性及抗H2O、抗SO2性能,并采用XRD、NH3-TPD和H2-TPR手段对催化剂的物理化学性质进行表征。结果表明,在无H2O和SO2存在的情况下,三种催化剂的低温SCR催化活性均比较高。相对来说,Mn/Ce-ZrO2在低温段(100～160℃)活性更高,Mn/P25在高温段(160～220℃)活性更高,这与两种催化剂的氧化还原性质有关。H2-TPR表征表明,Mn/Ce-ZrO2更容易发生氧化还原反应,而Mn/P25还原峰对应的温度较高、面积较大。三种催化剂均有很高的低温抗水性能。另外,Mn/Ce-ZrO2的抗H2O、抗SO2性能最好,而Mn/P25的抗H2O、抗SO2性能最差。Mn/Ce-ZrO2具有较好的抗H2O、抗SO2性能是由于其具有较多的表面酸位点,且表面生成的硫铵盐不稳定。

Three Mn-based catalysts of Mn/Ce-ZrO2, Mn/P25, and Mrl/A1203 with different supports were prepared by impregnation method and were used in the selective catalytic reduction of NO with NH3（ NH3-SCR） at low temperature. The catalysts were characterized by XRD, NH3-TPD and H2-TPR and their activity at low temperature as well as the resistances towards H2O and SO2 were investigated. The results showed that Mn/Ce- ZrO2 exhibits better activity at low temperature （ 100 - 160 ℃ ） than other two catalysts, while Mn,/P25 performs better at high temperature （160 -220 ℃ ）, which is related with the redox characteristics of the catalysts. Mn/ Ce-ZrO2 is more easily to be reduced at low temperature while Mn/P25 has a larger reduction peak at higher temperature, as revealed by Hz-TPR. All of the three catalysts have a good resistance to H2O; among them Mn/ Ce-ZrO2 exhibits the best resistance to SO2 and H2O, which should be attributed to the abundant acid sites and the instability of ammonia sulfate formed on the surface of Mn/Ce-ZrO2.