A solid-state NMR study of the molecular sieve VPI-5 synthesized in the presence of a CTABr surfactant

Silicon-free and silicon-rich large-pore aluminophospate VPI-5, synthesized with various contents of AlPO-H3 impurity, was studied by Bloch decay (BD) and cross polarization (CP) NMR under magic angle spinning (MAS). The H-1 --> P-31 CP peaks were considerably stronger from AlPO-H3 than from VPI-5. A detailed examination of the CP kinetics and a careful comparison of the CP and BD spectra are prerequisites for the unequivocal interpretation of H-1 --> P-31 CP in porous aluminophosphates. (C) 1997 Elsevier Science B.V.