Disorder in Zeolite SSZ-31 Described on the Basis of One-Dimensional Building Units

Abstract

A new description of the disorder in SSZ-31 is given on the basis of one-dimensional units consisting of tubular pores. The pores are formed of rolled-up honeycomb-like sheets of fused T6-rings (T = tetrahedral) and the pore aperture contains 12 T atoms. The 1-D units are arranged into different types of layers depending on whether the shift between adjacent pores in the layer is zero or one-half of the repeat distance along the pore. These layers of pores can be used to build three-dimensional framework structures. This approach has led to two new findings: first, two new polytypes have been foundin addition to eight polytypes previously describedand second, it is shown that it is possible to have intergrowths between all 10 polytypes and not only among selected groups of themas previously thought. Simulation of the X-ray diffraction patterns of disordered structures indicate that SSZ-31 is even a more disordered structure than previously reported. The disorder does not block the pores and the local por...