Preferential location of germanium in the UTL and IPC-2a zeolites

The preferential location of Ge in the double four-membered rings (D4R) of zeolite UTL has been examined with periodic density functional theory calculations. In silicate UTL, Ge atoms are preferentially sited at the T1 and T2 atoms in the D4R cages. The preference for siting Ge atoms at the D4R sites over other T atom sites in UTL increases as more Si atoms are replaced by Ge. Our calculations show that at least 3 Ge atoms can be located in the D4R cages before any appreciable occupancy at non-D4R sites. Comparison of Ge atom siting in UTL to zeolite IPC-2a shows that the single four-membered ring (S4R) sites in the latter are not the most favorable sites. (Figure Presented).