铜离子交换分子筛上NO吸附的IR光谱及TPD研究

采用原位IR光谱及TPD技术研究了NO在铜离子交换分子筛上各种表面物种的生成及脱附,并与NO在Cu-ZSM-5上的分解反应性能相关联,考察了Cu-ZSM-5反应活性高的原因及O₂的生成机理。NO的吸附状态随分子筛母体种类及铜离子交换度的不同而变化,交换度较高的ZSM-5催化剂上容易形成NO-3物种,该物种对NO分解及O₂的生成具有重要作用。

FTIR and TPD Studies of Adsorption Properties of Nitrogen Monooxide over Copper Ion-exchanged Zeolites

The relations of the adsorption properties and the behavior of catalytic decomposition of nitrogen monooxide over various copper ion-exchanged zeolites were studied by the means of in situ FTIR and temperature-programmed desorption (TPD). The results demonstrated that NO⁺, O^--Cu-NO and NO₃^- species were formed on the surface of the zeolites and desorbed at 350～400 K(denoted as α), 400～480 K(β) and 650～700 K(γ), respectively. It was found that the kinds and the amounts of the species were greatly changed with the zeolite structure and the copper ion exchange level, i. e . Cu-MFI, Cu-MOR and Cu-OFF/ERIgave α, β and γ peaks; Cu-FER gave α and β peaks; Cu -LTLand Cu-FAU only gave α peak. The amounts of desorption were increased linearly with the exchange level of copper on Cu-MFI. The O₂desorption peak appeared at the same temperature as that of the γ peak. In addition, by comparing the present results with the behavior of catalytic decomposition of NO, it is also found that NO₃^- species play a key role in the catalytic decomposition of NOand the formation of O₂over the zeolites.