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Open AccessArticle

Tetrapropylammonium Occlusion in Nanoaggregates of Precursor of Silicalite-1 Zeolite Studied by 1H and 13C NMR

1
Institut Lavoisier de Versailles, Tectospin, UMR CNRS 8180, Université de Versailles Saint-Quentin-en-Yvelines, 78035 Versailles cedex, France
2
Centre for Nanoporous Materials, School of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
*
Author to whom correspondence should be addressed.
Academic Editor: Gianfranco Pacchioni
Inorganics 2016, 4(2), 18; https://doi.org/10.3390/inorganics4020018
Received: 23 April 2016 / Revised: 18 May 2016 / Accepted: 24 May 2016 / Published: 1 June 2016
(This article belongs to the Special Issue Traversing the Boundaries of Inorganic Chemistry)
The dynamic behavior of tetrapropylammonium (TPA) cations in the clear precursor sols for silicalite synthesis has been investigated by 1H diffusion ordered spectroscopy (DOSY), T1, T2, and T 1H relaxation, as well as 1H→13C cross polarization (CP) nuclear magnetic resonance. The DOSY NMR experiments showed the presence of strong solute–solvent interactions in concentrated sols, which are decreasing upon dilution. Similarities in dependence of diffusion coefficients with fractional power of the viscosity constant observed for nanoparticles, TPA cations and water led to the conclusion that they aggregate as anisotropic silicate-TPA particles. Relaxation studies as well as 1H→13C CP experiments provide information on dynamic properties of ethanol, water and TPA cations, which are function of silicate aggregates. The general tendency showed that the presence of silicate as oligomers and particles decreases the relaxation times, in particular T2 and T1ρH, as a consequence of involvement of these latter in ion-pairing interactions with water-solvated TPA molecules slowing down their mobility. Furthermore, from the 1H→13C CP dynamics curve profiles a change in the CP transfer regime was observed from fast (TCH << T1ρH) for solutions without silicates to moderate (TCH~T1ρH) when silicates are interacting with the TPA cations that may reflect the occlusion of TPA into flexible silicate hydrate aggregates. View Full-Text
Keywords: silicalite; NMR spectroscopy; dynamics; DOSY silicalite; NMR spectroscopy; dynamics; DOSY
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MDPI and ACS Style

Haouas, M.; Petry, D.P.; Anderson, M.W.; Taulelle, F. Tetrapropylammonium Occlusion in Nanoaggregates of Precursor of Silicalite-1 Zeolite Studied by 1H and 13C NMR. Inorganics 2016, 4, 18.

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