LaHY分子筛的羟基及其酸性的红外分析

在原位红外光谱装置上, 通过氨的吸,脱附, 对脱水(320 ℃)LaHY分子筛上形成的羟基峰作了归属, 对酸性质作了进一步的分析. 其结果是: 除强酸性羟基3638 cm~(-1) (HY), 3631 cm~(-1)(LaHY)和3536 cm~(-1)(HY)、3556 cm~(-1)(LaHY)外, 还有二种直接与镧离子联结的羟基, 3520 cm~(-1)归属为弱酸性, 3531 cm~(-1)归属为非酸性. 从红外和固体核磁谱来说明, 超笼中高频羟基的酸强度是非均一的。

Studies on Acidity of Anhydrous LaHY Zeolite by In-Situ IR and Mas-NMR Method

Acidity of La~(3+)-exchanged HY zeolite has been studied by the measurements of adsorption on the in-situ IR system and MAS-NMR method. The results show that: 1.The IR bands at 3631 and 3556 cm~(-1) are all assigned to hydroxyl group of strong acidic sites. The band at 3531 cm~(-1) is assigned to nonacidic hydroxyl group, since it has no interaction with ammonia. It is possible that two hydroxyl groups coor-dinate with one La~(3+) directly; the band at 3520 cm~(-1) is assigned to weak acidic hy-droxyl group, because it has weak interaction with ammonia, and one hydroxyl group may coordinate with one La~(3+) directly.2. The hydroxyl group at 3638 cm~(-1), which is in supercage of HY Zeolite, is of heterogeneity of actidity resulting from silicon atoms with different numbers of coordinated Aluminium.