REMOVAL OF NITROGEN MONOXIDE THROUGH A NOVEL CATALYTIC PROCESS .2. INFRARED STUDY ON SURFACE-REACTION OF NITROGEN MONOXIDE ADSORBED ON COPPER ION-EXCHANGED ZSM-5 ZEOLITES
REMOVAL OF NITROGEN MONOXIDE THROUGH A NOVEL CATALYTIC PROCESS .2. INFRARED STUDY ON SURFACE-REACTION OF NITROGEN MONOXIDE ADSORBED ON COPPER ION-EXCHANGED ZSM-5 ZEOLITES
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DOI：
10.1021/j100202a055
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发表时间：
1992-11-12
影响因子：
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通讯作者：
KAGAWA, S
中科院分区：
文献类型：
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作者：
IWAMOTO, M;YAHIRO, H;KAGAWA, S
采用红外光谱结合各向同性示踪法研究了铜离子交换ZSM-5沸石对NO的吸附作用，阐明了NO催化分解的反应机理。已检测到三种不同的吸附 NO 状态，分别为 NO(delta+)、NO(delta-) 和 (NO)2delta-。 1827-cm-1 和 1734-cm-1 谱带的强度、二聚体的对称和不对称伸缩振动分别得出结论，(NO)2delta- 中 ON-Cu-NO 的键角为 103 度。对真空、氧化或 CO 预吸附的铜离子交换 ZSM-5 沸石进行的红外实验以及 ESR 或磷光测量表明，NO(δ-) 和 (NO)2δ- 在铜 (I) 离子上形成，而 NO(δ+) 在铜 (II) 离子上形成。阴离子物质的形成取决于NO的分压，NO(delta-)(ads) + NO(ps) --> (NO)2delta-(ads)。在环境温度下，NO(δ-)和(NO)2δ-的红外波段强度随着反应时间的延长而降低，而NO(δ+)的红外波段强度则增加。测量了气相中产物分布随吸附时间的变化，并证实即使在室温下真空样品上也会形成 N2 和 N2O。由此可见，Cu+离子是活性中心，NO(δ-)和/或(NO)2δ-物种是铜离子交换ZSM-5沸石催化剂上NO分解的中间体，催化反应循环在573 K或以上进行，在该温度下分解产生的氧气可以解吸。
Infrared spectroscopy combined with an isotropic tracer method has been used to study the adsorption of NO over copper ion-exchanged ZSM-5 zeolites and to elucidate the reaction mechanism of catalytic decomposition of NO. Three distinct states of adsorbed NO have been detected, being attributed to NO(delta+), NO(delta-), and (NO)2delta-. The intensities of 1827- and 1734-cm-1 bands, symmetric and asymmetric stretching vibration of the dimer species, respectively, concluded that the bond angle ON-Cu-NO in (NO)2delta- is 103-degrees. The IR experiments on evacuated, oxidized, or CO-preadsorbed copper ion-exchanged ZSM-5 zeolites and ESR or phosphorescence measurements indicated that NO(delta-) and (NO)2delta- are formed on copper(I) ions while NO(delta+) on copper(II) ions. The formation of the anionic species depended on the partial pressure of NO, NO(delta-)(ads) + NO(ps) --> (NO)2delta-(ads). The intensities of the infrared bands attributable to NO(delta-) and (NO)2delta- decreased at ambient temperature with reaction time, while that of NO(delta+) increased. The change of the distribution of products in the gas phase with adsorption time was measured and the formation of N2 and N2O was confirmed even at room temperature on the evacuated sample. It follows that the Cu+ ions are active centers, NO(delta-) and/or (NO)2delta- species are intermediates for the decomposition of NO over copper ion-exchanged ZSM-5 zeolite catalyst, and the catalytic reaction cycle proceeds at or above 573 K, at which oxygen generated through the decomposition can desorb.