Changes of intermediate-range structure in the course of crystallization of zeolite beta

Abstract

Silicate-ring structure in a dry silicate gel that can be transformed into zeolite beta by the steam-assisted crystallization (SAC) was investigated using high-energy X-ray diffraction (HEXRD). In total correlation function, T( r), determined from HEXRD data, a dry gel that was crystallized to zeolite beta exhibited a remarkable peak at 3.8 Å corresponding to second-neighbor Si–O separations in a 4-membered ring (4MR). The 29Si NMR results supported the existence of a large number of 4MRs in the dry gel with TEA +/Si = 0.37. The 4MRs in the dry gel, which are derived from double 3-memebered ring (D3R) structures stabilized by TEA + in TEA +–silicate solution, are essential in the formation of zeolite beta by the SAC method.