Studio computazionale sulla stabilità e la locazione dei siti di Ti nel reticolo MFI del catalizzatore TS-1

Nowadays the scientific and industrial interest about zeolites is increasing. One of the most interesting family of these material is the MFI: characterized by an anisotropic framework intersecting two ten-membered rings channel, with respectively straight circular and sinusoidal elliptical opened channels. The Titanium silicalite-1 (TS-1) belongs to this group and its peculiarity is the presence of Ti atom as an isomorphous substitution of Si (about 1 atom per cell) at tetrahedral framework sites (T). The low amount of Ti in TS-1 gives single site heterogeneous catalytic property to this material. Because of this, TS-1 is largely employed in the industry. The scientific interest is focused on the structure of this material, because the real position of Ti atoms is not well defined. In fact, from the literature it is possible to find conflicting data ether in the experimental or in the theoretical studies. In this open contest we have performed a theoretical ab-initio periodic study that aims to identify and locate the Ti-sites and the consequent material stability, considering a Pnma symmetry and a Ti content corresponding to 2.63 wt% in TiO2.