Structure of natural and NH (sub 4) -exchanged Sasbach faujasite; a single-crystal study

The interest for the environmental, industrial and technological applications of Si-rich zeolites is very high. Among the large-pore zeolites, faujasite is one of the most exploited. The aim of this paper is to obtain detailed structural information on natural and NH (sub 4) -exchanged faujasite before using this zeolite for dealumination tests, targeting the realization of large single crystals of all-silica faujasite. As one of the most Si-rich natural samples, faujasite from Sasbach (Na (sub 13.64) K (sub 0.87) Mg (sub 10.46) Ca (sub 8.89) Sr (sub 0.34) (Al (sub 51.95) Si (sub 139.57) )O (sub 384) . 272.29 H (sub 2) O; space group Fd-3m;a = 24.6906(2) Aa) was chosen for study. Single-crystal X-ray diffraction structural refinements of both natural and NH (sub 4) -exchanged samples are reported and discussed. In the natural faujasite sample, almost all the extra framework species could be located for the first time. In the NH (sub 4) -exchanged sample the ammonium and water molecule sites were located. Ammonium cations occupy two of the sites occupied by the extra framework species in the original mineral.