Background and Recent Advances in Ti-Containing Zeolite Materials

The incorporation of Ti into the silica framework of zeolites has paved the way for the use of the crystalline microporous solids as shape-selective catalysts for oxidation reactions. This was realized in 1983, when the synthesis of TS-1 and its catalytic properties in the oxidation of several organic substrates with diluted H2O2 under mild conditions were claimed. From then on, the TS-1 has been the subject of numerous and in-depth studies aimed at its improvement and understanding of its characteristics, in particular, of the structure of the Ti site. The first part of this chapter is devoted to the synthesis of the TS-1 from its origins to present days, when the focus is on the preparation of materials with hierarchical porosity. A great emphasis is given to the characterization of this material, with particular attention to the structure of the Ti site, to the evaluation of the maximum content of Ti, and to the possible existence of preferential sites for localization of the heteroatom in the framework. The final part of the chapter is devoted to review the synthesis of other Ti-containing zeolites, very promising systems but, with few exceptions (e.g., Ti-beta), still poorly studied.