TITANIUM BORALITES WITH MFI STRUCTURE CHARACTERIZED USING XRD, XANES, IR, AND UV-VISIBLE TECHNIQUES - EFFECT OF HYDROGEN PEROXIDE ON THE PREPARATION

摘要

Peroxytitanate, boric acid, and a controlled excess of hydrogen peroxide have been added to the preparation mixture of silicalites to synthesize titanium boralites, TBS-1, of MFI structure. After crystallization, the unit cell expansion at a constant boron substitution level of 2.7% indicates that titanium is, like boron, incorporated in the framework. The simultaneous incorporation of Ti and B is confirmed by characteristic IR bands at 920, 960, and 1380 cm(-1). Reflectance UV-visible spectroscopy reveals that, in the presence of boron, there is always a formation of extraframework oxide clusters with an anatase-like structure identified by XANES at the Ti K-edge. The striking similarity between the Ti K-edges of framework tetrahedral Ti sites in TBS-1 and boron-free TS-1 indicates that the sites are more likely identical in both materials. A quantification of the extraframework Ti species from the edges clearly evidences that, in the presence of boron, more hydrogen peroxide is necessary in the gel to optimize the incorporation of Ti in the framework. (C) 1995 Academic Press, Inc. [References: 55]