磷钨酸“瓶中船”型催化剂的合成、表征及催化分解NO_x性能

Preparation,Characterization and NO_x Catalytic Decomposition Behavior of Ship-in-Bottle Type H_3PW_(12)O_(40)-NaY Catalyst

采用原位合成的方法 ,在微波辐射条件下制备了样品NH4PW-NaY,并通过FTIR、XRD、低温氮吸附-脱附等手段确认了该样品为磷钨酸铵(NH4PW)存在于NaY沸石超笼中的"瓶中船"型催化剂。通过NH4PW与NOx反应生成磷钨酸(HPW)的方式将NH4PW-NaY转化为HPW-NaY,并通过红外及红外吡啶吸附等表征手段证实了NaY沸石超笼中只含有磷钨酸的"瓶中船"型催化剂HPW-NaY被首次制备。随后研究了该催化剂对NOx的吸附-脱附性能,结果表明,在吸附温度为170℃时,HPW-NaY对浓度为1 696 mg.m-3的NOx吸附容量为2.38 mgNOx.gcat-1,在通水蒸汽条件下,催化剂温度降至100℃时所吸附的NOx发生脱附,脱附后的催化剂可重复使用。最后通过程序升温脱附-质谱(TPD-MS)研究了HPW-NaY对NOx的催化分解性能,结果发现NOx在以NaY沸石为载体的HPW上的分解过程中有O2产生,且氧的产生滞后于N2O及N2,HPW-NaY催化分解NOx的转化率及N2选择性分别为61%与75%,均高于单纯HPW催化剂。

The ＂ship-in-bottle＂ catalyst NH,PW-NaY was synthesized under microwave radiation and characterized by FTIR, XRD and low temperature N2 adsorption-desorption. HPW-NaY was produced from NH4PW-NaY by the in situ reaction of NH,PW with nitrogen oxides （NOx）. FTIR and in situ pyridine adsorption IR confirmed that HPW-NaY with encaged HPW was prepared successfully for the first time. The NOx adsorption-desorption on HPW-NaY was investigated, and the results showed that 2.38 mgNo .g-1 was adsorbed at 170 ~C, and the adsorbed NOx could be desorbed under coding in wet air. After NO~ desorption, the HPW-NaY could be reused without regeneration. Finally, temperature-programmed desorption coupled with mass spectroscopy （TPD-MS） was carried out on HPW-NaY filled with NOx to probe into its ability to catalyze NOx decomposition. O2 formation was observed, which lags a little behind the appearance of N2O and N2 on HPW- NaY. The NOx conversion is 61% with N2 selectivity of 75%, which is higher than that on pure HPW.