John B. Higgins

The framework topology of zeolite beta

The tetrahedral framework structure of zeolite beta is disordered along [001]. The disordered beta framework and three simple ordered polytypes are related through layer displacements on 001 planes. Three mutually perpendicular 12-ring channel systems are characteristic of the three ordered polytypes and the disordered beta structure. The proposed framework structures are consistent with the known diffraction, sorption, and cation-exchange properties of zeolite beta.

Framework topology of AIPO4-8: the first 14-ring molecular sieve

The framework topology of AIPO 4 -8, a synthetic aluminophosphate molecular sieve, has been determined via model building followed by DLS-refinement and powder pattern simulation. AIPO 4 -8 has been shown to possess a unidimensional 14-ring channel system with pore dimensions 7.9×8.7 A.

The framework topology of ZSM-57: A new synthetic zeolite

ZSM-57 is a new zeolitic phase with a novel framework topology: structure code MFS, space group lmm2, a = 7.4510(7)A, b = 14.1711(8)A, c = 18.767(2)A, 18.2T/1000 A3. Although the structure is closely related to ZSM-35 (FER), ZSM-57 has 4-rings lacking in the ferrierite framework. There is a channel system of intersecting 8- and 10-rings. Although the dimensions of the 8-ring (3.5 × 4.8A) channel differ only marginally from ZSM-35, the 10-ring channels (5.1 × 5.8A) are significantly larger than are the analogous channels in ZSM-35 and slightly larger than are the 10-rings in ZSM-5.

ZSM-10: Synthesis and tetrahedral framework structure

A reproducible, scaleable synthesis of ZSM-10 is reported. This synthesis is dependent on the presence of 1,4-dimethyl-DABCO cations during the nucleation/aging stage, but this directing agent is not incorporated in the final product. Analysis of the zeolite product during aging shows that offretite is formed first and then converts to ZSM-10. The framework topology of ZSM-10 (K24Al24Si84O216 · xH2O · yR) has been determined from synchrotron X-ray and electron diffraction data, model building, and X-ray powder pattern simulation. ZSM-10 has a large hexagonal unit cell with a = 31.575(7) A, c = 7.525(4) A, P6/mmm maximum topological symmetry, and a tetrahedral framework density of 16.6 T/1,000 A3. The tetrahedral framework is constructed from columns of alternating cancrinite cages and double 6-rings which also build the LTL (Linde Type L or zeolite L) and OFF (offretite) frameworks. Two different one-dimensional, 12-ring pore systems parallel the caxis in ZSM-10. One 12-ring channel is topologically identical to the undulating channel in the LTL framework, and the other is identical to the 12-ring channel in the OFF framework. ZSM-10 appears to be the first zeolite with two distinct, parallel, 12-ring channel systems that occur individually in other zeolites.

Multifield magic-angle spinning and double-rotation nuclear magnetic resonance studies of a hydrated aluminophosphate molecular sieve: AlPO4-H2

AlPO4-H2 is a microporous hydrated aluminophosphate, structurally related to VPI-5, whose framework has highly elliptical 10-ring channels (2.9 x 7.6 A) parallel to the c crystallographic axis. To resolve a previously reported discrepancy between nuclear magnetic resonance (NMR) and X-ray diffraction (XRD) data a highly crystalline AlPO4-H2 has been further characterized with 27Al and 31P magic-angle spinning (MAS) NMR at 11.7 T and 27Al double-rotation (DOR) NMR at 4.7 T. These present NMR data definitively show that the true space group symmetry of the AlPO4-H2 framework structure is triclinic rather than the higher orthorhombic symmetry proposed earlier from XRD studies.