29Si{27Al} TRAPDOR MAS NMR to distinguish Qn(mAl) sites in aluminosilicates. Test case: Faujasite-type zeolites

S Greiser; M Hunger; C Jäger

doi:10.1016/j.ssnmr.2016.10.004

²⁹Si{²⁷Al} TRAPDOR MAS NMR to distinguish Qⁿ(mAl) sites in aluminosilicates. Test case: Faujasite-type zeolites

Solid State Nucl Magn Reson. 2016 Oct:79:6-10. doi: 10.1016/j.ssnmr.2016.10.004. Epub 2016 Oct 8.

Authors

S Greiser¹, M Hunger², C Jäger³

Affiliations

¹ Bundesanstalt für Materialforschung und -prüfung (BAM), Division 1.3 Structure Analysis, Richard-Willstätter-Str. 11, 12489 Berlin, Germany.
² University of Stuttgart, Institute of Chemical Technology, Pfaffenwaldring 55, 70550 Stuttgart, Germany.
³ Bundesanstalt für Materialforschung und -prüfung (BAM), Division 1.3 Structure Analysis, Richard-Willstätter-Str. 11, 12489 Berlin, Germany. Electronic address: christian.jaeger@bam.de.

PMID: 27750080
DOI: 10.1016/j.ssnmr.2016.10.004

Abstract

²⁹Si{²⁷Al} TRAPDOR MAS NMR was applied to two faujasite-type zeolites with Si/Al ratios of 1.3 (Na-X) and 2.7 (Na-Y). The aim of this test study is to show that different Q⁴(mAl) sites (m =4, 3, 2, 1) can be distinguished by differently strong TRAPDOR effects (ΔS/S₀). Indeed, it was found that the TRAPDOR effect depends on the number m of AlO₄ units connected to the Q⁴ silicon tetrahedrons. For Na-X, the measured ΔS/S₀ values are 1 : 0.81 : 0.56 for Q⁴(4Al), Q⁴(3Al) and Q⁴(2Al), respectively (normalized to Q⁴(4Al)). The corresponding ΔS/S₀ values are the same for Na-Y within the error bars, although the silicon sites are different: Q⁴(3Al), Q⁴(2Al) and Q⁴(1Al) and now normalized to Q⁴(3Al) as no Q⁴(4Al) is present. Nevertheless, the proposed method opens up the possibility to distinguish overlapping ²⁹Si NMR signals of the Qⁿ(mAl) sites in amorphous materials as the main goal of these investigations.

Keywords: (29)Si{(27)Al} TRAPDOR MAS NMR; Aluminosilicates; Faujasite-type zeolites; Q(4)(mAl) sites; Solid-state NMR.