XE-129 NMR-STUDY OF VPI-5 AND ALPO4-8 MOLECULAR-SIEVES

Combined xenon-129 n.m.r. and X-ray diffraction techniques have been used to characterize two novel molecular sieves, VPl-5 and AlPO4-8. By comparing the literature data, it can be concluded that VPl-5 contains generally not only extralarge pores, about 12.5 angstrom in diameter, but also pores of about 10.7 angstrom in diameter. These latter could be a very well-defined structural defect corresponding to 16 T-ring channels. Calcination of hydrated VPl-5 in a stream of air results in another molecular sieve: AlPO4-8. In contrast to VPl-5, AlPO4-8 contains no extralarge pores, but has pores about the same size of those of AIPO4-5 (approximately 7.3 angstrom).