title: 29Si{27Al} TRAPDOR MAS NMR to distinguish Qn(mAl) sites in aluminosilicates. Test case: Faujasite-type zeolites.
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 AlO4units connected to the Q4silicon tetrahedrons. For Na-X, the measured ΔS/S0values are 1 : 0.81 : 0.56 for Q4(4Al), Q4(3Al) and Q4(2Al), respectively (normalized to Q4(4Al)). The corresponding ΔS/S0values 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 overlapping29Si NMR signals of the Qn(mAl) sites in amorphous materials as the main goal of these investigations.
authors.affiliation: Bundesanstalt für Materialforschung und -prüfung (BAM), Division 1.3 Structure Analysis, Richard-Willstätter-Str. 11, 12489 Berlin, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Greiser
authors.affiliation: University of Stuttgart, Institute of Chemical Technology, Pfaffenwaldring 55, 70550 Stuttgart, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Hunger
authors.affiliation: Bundesanstalt für Materialforschung und -prüfung (BAM), Division 1.3 Structure Analysis, Richard-Willstätter-Str. 11, 12489 Berlin, Germany. Electronic address: christian.jaeger@bam.de.
authors.forename: C
authors.initials: C
authors.lastname: Jäger
keywords: (29)Si{(27)Al} TRAPDOR MAS NMR; Aluminosilicates; Faujasite-type zeolites; Q(4)(mAl) sites; Solid-state NMR