MnO2/NH4NaY 催化剂上的NO低温选择性催化还原（SCR）

研究了NO在新型MnO₂/NH₄NaY催化剂上的低温转化行为，并对MnO₂/NH₄NaY的再生及稳态操作进行了考察。结果表明，以MnO₂/NaY为母体，用硫酸铵溶液离子交换制备的新型MnO₂/NH₄⁺NaY分子筛催化剂具有良好的低温活性，120 ℃时，NO转化率近100％。但催化剂不能在高于150 ℃的反应温度下操作，防止NH₄⁺挥发解吸。离子交换过程中，NH₄⁺的交换度可达40%，在120 ℃、氧体积分数6%、空速3 000h^-1和水体积分数7%和无外加还原剂条件下，MnO₂/NH₄NaY可保证入口浓度为1 000×10^-6的NOx在连续7 h内达到完全转化。在高空速（12 000 h^-1）有稳定氨源下，于MnO₂/NH₄NaY上进行的SCR稳态实验充分证明，存在于MnO₂/NH₄NaY的NH₄⁺对催化反应明显有利。 它可使NH₃与NOx物质的量比从以往的1.2降至1，大大减少由于NH₃泄露而造成的二次污染。

Low temperature selective catalytic reduction(SCR)of No over MnO2/NH4NaY catalyst

Selective catalytic reduction of NO at low temperature over a newly-developed MnO₂/NH₄NaY catalyst was studied, as well as regeneration and steady operation of the catalyst. The results showed that the newly-developed MnO₂/NH₄NaY catalyst prepared by ion-exchange between ammonium sulphate and MnO₂/NaY had good low-temperature activity, with NO conversion approaching 100% at 120 ℃, but it was not usable at over 150 ℃, which resulted in volatilization of NH₄⁺. NH+4 exchanging extent of up to 40% was attained. The MnO₂/NH₄NaY catalyst could completely convert NOx with inlet concentration of 1 000×10^-6 to N₂ for continuous 7 h under the following condition: 120 ℃, 6%O₂ (volumetric fraction）, GHSV 3 000 h^-1 , 7% H₂O(volumetric fraction) , without additional reductant. Steady-state experiment with stable NH3 source at high GHSV 12 000 h^-1 proved that NH₄⁺ in MnO₂/NH₄NaY was beneficial to SCR of NO, with NH₃/NOx molar ratio reduced from 1.2 to 1, thus remarkably lowered the secondary pollution caused by NH₃.