ERS-18: A new member of the NON-EUO-NES zeolite family

摘要

ERS-18, a new small pore high silica zeolite, was synthesized using 6-azonia-spiro-[5,5]-undecane hydroxide as structure directing agent. Its crystal structure was determined ab initio by using high-resolution synchrotron X-ray powder diffraction data and the zeolite-dedicated software FOCUS. ERS-18 shows orthorhombic symmetry (s.g. Fmmm) setting with unit cell parameters: a = 34.989, b = 13.667 and c = 22.559 A. The values of b and c parameters are in common with zeolites of the NON-EUO-NES family (IZA codes for nonasil, EU-1, and NU-87, respectively); within this group the a parameter, corresponding to the layer stacking direction, varies from ~15.0 (NON) to ~20.0 (EUO), to ~25.0 A (NES). Therefore, ERS-18 can be regarded as a new member of this family having the longest stacking parameter (i.e. ~35.0 A) reported so far. The ERS-18 framework is characterized by the presence of 8-ring channels (crystallographic free dimensions: 3.1 x 2.5 A) running along the [0 1 0] direction and supercages delimited by 12-rings (crystallographic free dimensions: 6.1 x 5.2 A, cross section; 18.4 A, depth) aligned along [100] and off the 8-ring channels.