Enhanced resolution of Al sites in the molecular sieve SAPO-37 by 27Al MQ MAS NMR

Abstract

The Al coordination state of molecular sieve SAPO-37 has been studied by 27Al multiple quantum (MQ) MAS NMR spectroscopy. Although the 1D 27Al MAS NMR spectrum of the aluminum sites show a complex pattern, the 3Q MAS NMR spectra of SAPO-37, submitted to different treatments, lead to the detection of four different Al species in the as-synthesized sample. The comparison of the MQ spectra of the as-synthesized sample, as well as of the dehydrated, partial template extracted, and full template calcined samples, made it possible to distinguish: (i) tetrahedral Al sites with 4P; (ii) tetrahedral Al sites with one (or more) Si as nearest neighbors interacting with TPA, and framework Al coordinated with; (iii) TMA; or (iv) water.