关键词: &beta, 沸石结构, 骨架外阳离子位置, 质子酸位

Abstract: On the basis of fundamental principle of structural chemistry and through atom distance-least-square refinement, the non-framework cation locations in zeolite beta were determined, which was then confirmed by X-ray scattering experiment analysis using Cu²⁺as the probe ion. The result shows that in the stack faulting structure of zeolite beta, the non framework cation positions lie in the 12-membered ring intersecting channels, near the double six memberedring of building unit Ⅰ and coordinated by six framework oxygen atoms. These cation positions belong to six kinds of different crystallographic sites: two sets of equivalent positions in polytype A, one set in polytype Band three sets in polytype C. The geometric circumstances and the coordination state around the cations are very similar to each other and the average coordination bonding distances of M_O are almost equal, so all the non-framework cations in zeolite beta act as one type of cations. Correspondingly, zeolite Hβ has only one kind of Brnsted acid sites, which was also proved by the NH₃-TPD curves of the samples. The cations with this kind of distribution can contact with reagent molecules easily and efficiently. Therefore it can be conclude that Hβ is a kind of acid catalyst with a high activity and excellent selectivity, and M-zeolite beta may become a potential redox catalyst.

Key words: Structure of zeolite beta, Non-framework cation location, Brnsted acid site