Na6Zn2[Al6Si6O24](SO4)2 was prepared as a stoichiometric phase by reacting zeolite A with ZnSO4 at 700 °C for 8 h. Powder-XRD showed that Na6Zn2[Al6Si6O24](SO4)2 crystallised with the sodalite structure, a = 8.923(1) Å, Z = 1; illustrating that Zn2+ can be substituted for Ca2+ in ideal haüyne, Na6Ca2[Al6Si6O24](SO4)2. Na6Zn2[Al6Si6O24](SO4)2 was shown to be largely immiscible with nosean, Na8[Al6Si6O24]SO4 in the solid-state. Na6Zn2[Al6Si6O24](SO4)2 decomposes above 700 °C, yielding nosean, Na8[Al6Si6O24]SO4; willemite, Zn2SiO4; gahnite, ZnAl2O4; and presumably a glass phase, 2Na2O•9SiO2; with the loss of gaseous SO3. Na6Zn2[Al6Si6O24](SO4)2 was annealed under hydrogen at 700 °C, yielding sphalerite, ZnS and a more voluminous sodalite, Na6[AlSiO4]6 (a = 9.068(1) Å, Z = 1). Solid-state NMR indicates that the aluminosilicate framework remains essentially unchanged (according to the 29Si and 27Al) throughout this reaction, with the largest change observed for 23Na.
Microporous and Mesoporous Materials, 2012, Vol 161, p. 91-97