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

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