Studies on the crystallization process of titanium silicalite-1 (TS-1) synthesized using tetrapropylammonium bromide as a template

Tetrapropylammonium bromide (TPABr) has been used as a template for the syn thesis of titanium silicalite-l (TS-l), and the involved crystallization me chanism and the characteristics of the incorporated Ti in the zeolites were investigated by applying a variety of methods, e.g. solid-state NMR, IR, U V-VIS, XRD and SEM, as well as pH-meter techniques. It is revealed that the crystallization process performed with TPABr follows the well-known soluti on-mediated transformation mechanism, and that the Ti atoms were introduced into the frameworks synchronously with the formation of the zeolite struct ures. In addition, the formation of less amount of inactive TiO2 crystals w ith an anatase structure is not in the initial stage of the crystallization as reported by some authors, but through the whole process of the zeolite synthesis, which suggests that a careful control of the synthesis parameter s throughout the whole crystallization process is quite important for obtai ning the anatase-free titanium-silicalite zeolite. (C) 2000 Elsevier Scienc e S.A. All rights reserved.