Crystalline microporous titanium silicates

This paper surveys several issues related to the invention of titanosilicate molecular sieves and their implementation as oxidation catalysts using peroxide and olefinic substrates. The concept has already progressed to the successful commercialization of the TS-1 catalyst, carried out by EniChem. There are a number of synthetic challenges to producing these materials and having the titanium substitution yield an effective catalyst. The TS-1 could oxidize a certain set of substrates which were capable of entering the MFI pore system. The challenge of selective oxidations in larger substrates, of greater interest to the fine chemicals sector, has been partially met by the development of synthesis routes to larger pore titanosilicate zeolites, beta, SSZ-33, and UTD-1. Potential applications for selective oxidations are reviewed. To better understand these chemical reactions, mechanistic considerations concerning the oxidations are discussed and the arguments are highlighted by some computational analyses. Finally, the commercial process is discussed. Economic drivers and limitations are presented to help focus where future progress can be made.