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 synthesis of titanium silicalite-1 (TS-1), and the involved crystallization mechanism and the characteristics of the incorporated Ti in the zeolites were investigated by applying a variety of methods, e.g. solid-state NMR, IR, UV–VIS, XRD and SEM, as well as pH-meter techniques. It is revealed that the crystallization process performed with TPABr follows the well-known solution-mediated transformation mechanism, and that the Ti atoms were introduced into the frameworks synchronously with the formation of the zeolite structures. In addition, the formation of less amount of inactive TiO2 crystals with 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 parameters throughout the whole crystallization process is quite important for obtaining the anatase-free titanium–silicalite zeolite.