MnO_2/NaY催化剂上NH_3低温选择催化还原NO_x

研究了温度、气态空速、氧含量、水蒸气以及进料气组成对M nO2/NaY催化剂上NH3低温选择催化还原(SCR)NOx的影响,探讨了水蒸气存在下该催化剂上NOx的还原机理。实验结果表明,M nO2/NaY催化剂具有良好的低温SCR催化活性,在无水蒸气存在条件下,当原料气中φ(NO)=0.1%、φ(O2)=6%、n(NH3)∶n(NOx)=1.2、温度120℃、气态空速5 000h-1时,NO转化率达到98%;在水蒸气体积分数10%的条件下,150℃时NO转化率接近90%,但当温度低于100℃时,NO转化率迅速下降。原料气组成对NO转化率有较大影响,n(NO)∶n(NO2)=1时,NOx的转化率最高。水蒸气存在条件下,M nO2/NaY催化剂上NH3选择催化还原NOx的反应机理类似于重氮化反应机理。

Selective Catalytic Reduction of NOx with NH3 over MnO2/NaY Catalyst at Low Temperature

Selective catalytic reduction(SCR)of NO_x with NH_3 on MnO_2/NaY catalyst at low temperature was studied.Effects of reaction temperature,gas hourly space velocity(GHSV),steam,oxygen content and feed composition on NO_x conversion were examined.Mechanism of NO_x reduction in presence of steam was discussed.MnO_2/NaY catalyst had good SCR activity at low temperature.Under following conditions:without steam,φ(NO in feed)=0.1%,φ(O_2)=6%,n(NH_3) ∶(n(NO_x)=)1.2,temperature 120℃,and GHSV 5 000h~(-1),98% NO could be converted to N_2 and even in presence of steam volume fraction 10% the conversion could keep 90% at 150℃.But in presence of steam,when the temperature was lower than 100℃,the catalyst was almost inactive,because the existing water restrained oxidation capability of MnO_2.Feed composition could greatly affect conversion and when(n(NO)) ∶n(NO_2)=1,the best NO_x removal effect could be obtained.SCR mechanism of NO_x with NH_3 in presence of steam on MnO_2/NaY catalyst was similar to diazotization.