High silica zeolites with three-dimensional systems of large pore channels

Several high silica zeolites with three-dimensional systems of large pore channels have been prepared in aqueous fluoride media: Beta, ITQ-7, ITQ-10 and ITQ-14. Pure silica beta can crystallize using up to 17 organic cations considerably different in size, shape, rigidity and CIN ratios. There are clear differences in the powder X-ray diffraction patterns of calcined beta materials prepared with different cations, suggesting structural differences between them. However, this technique cannot be readily used to get further insights into these differences. (19)F MAS NMR spectroscopy shows the existence of fluoride occluded in double four ring cages in most of the different betas, thus demonstrating for the first time the real occurrence in these intergrown materials of polymorphs different from A and B. Double four ring cages are also present in ITQ-7 and in the new ITQ-10 and ITQ-14 zeolites. (C) 2001 Elsevier Science BN. All rights reserved.