Spectroscopic study of the surface of zeolite Y. II. Infrared spectra of structural hydroxyl groups and adsorbed water on alkali, alkaline earth, and rare earth ion-exchanged zeolites
Spectroscopic study of the surface of zeolite Y. II. Infrared spectra of structural hydroxyl groups and adsorbed water on alkali, alkaline earth, and rare earth ion-exchanged zeolites
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DOI：
10.1021/j100858a046
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发表时间：
1968-11
期刊：
影响因子：
--
通讯作者：
J. W. Ward
中科院分区：
文献类型：
--
作者：
J. W. Ward
观察了碱、碱土和稀土Y型沸石在不同温度下脱水和复水化过程中的红外光谱。碱阳离子Y型分子筛未观察到结构羟基。再吸附的水通过与可交换阳离子的结合而被简单地物理吸附。没有形成新的结构羟基。吸附水的吸收带的频率随阳离子半径而变化，因此随计算的静电场和电位而变化，也随电离电位而变化。结果与Habgood对碱阳离子X沸石的研究结果相似。对NaX沸石的检查在大多数方面证实了Habgood的结果。碱阳离子沸石对水的吸附是高度可逆的。Y型沸石钡的脱水和再水合形式类似于碱阳离子。镁、钙和锶Y分子筛的光谱均显示出结构羟基。3640和3540 cm-1附近的吸收带被认为与去离子化沸石中观察到的相同，代表硅烷醇基团。3600-3560 cm-1区域的吸收带被鉴定为与二价阳离子相关的羟基，而3690 cm-1附近的吸收带是由于吸附未解离的水。再水合作用在3690 cm-1附近产生一个强条带，当沸石加热到200℃以上时，该条带随着3640和3600-3560 cm-1附近条带的生长同时消失。后一个波段对水化水平非常敏感，可能表明MOH+很容易转化为氧化物。该波段的频率随阳离子有规律地变化，证实了该波段与阳离子的连接。稀土Y型分子筛的光谱显示，在3640和3522 cm-1处有两个优势羟基带，分别属于硅烷醇基团和MOH基团。水以高度可逆的方式吸附。没有形成新的结构羟基。
Infrared spectra of alkali, alkaline earth, and rare earth Y zeolites have been observed during dehydration and subsequent rehydration at various temperatures. No structural hydroxyl groups were observed for the alkali cation Y zeolites. Readsorbed water simply physically adsorbed by association with theexchangeable cations. No new structural hydroxyl groups were formed. The frequency of the absorption bands of the adsorbed water varied with the cation radius and hence with the calculated electrostatic field and potential and with the ionization potential. The results were similar to those foundfor alkali cation X zeolites by Habgood. An examination of NaX zeolite confirmed the results of Habgood in most respects. The adsorp-tion of water on the alkali cation zeolites is highly reversible. Barium Y zeolite dehydrated and rehydrated analogous to the alkali cation forms. Spectra of magnesium, calcium, and strontium Y zeolites all showed structural hydroxyl groups. The absorption bands near 3640 and 3540 cm-1 are considered to be the same as observed in decationized zeolites and represent silanol groups. An absorption band in the 3600-3560-cm-1 region is identified with hydroxyl groups associated with the divalent cations, while a band near 3690 cm-1 is due to adsorbed undissociated water. Rehydration produces a strong band near 3690 cm-1, which, when the zeolite is heated above 200, disappears simultaneously with the growth of bands near 3640 and 3600-3560 cm-1. The latter band is very sensitive to the hydration level, probably indicating that the MOH+ species is readily converted to theoxide. Confirmation of this band representing attachment to the cation is shown by the regular variation of its frequency with cation. Spectra of the rare earth Y zeolite showed two dominant hydroxyl bands at 3640 and 3522 cm-1 assigned to silanol groups and MOH groups. Water adsorbed in a highly reversible manner. No new structural hydroxyl groups were formed.