129Xe n.m.r. study of VPI-5 and AIPO 4-8 molecular sieves

Abstract

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