Combined in situ 29Si NMR and small-angle X-ray scattering study of precursors in MFI zeolite formation from silicic acid in TPAOH solutions

Houssin, Christophe J. Y.; Kirschhock, Christine; Magusin, Pieter C. M. M.; Mojet, Barbara; Grobet, Piet J.; Jacobs, Pierre; Martens, Johan A.; Santen, Rutger A. van

doi:10.1039/b306988p

Cited by 67 publications

(88 citation statements)

References 31 publications

(36 reference statements)

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“…Some believe that the silica nanoparticles do not participate in nucleation directly, but dissolve and serve as nutrients during crystallization [8,27,28] others assume the direct incorporation of formed nanoparticles into the growing crystals. This could be accomplished via an aggregation mechanism [5,16,23,[29][30][31][32] in which these nanoparticles either already resemble the MFI structure [29][30][31] or exhibit a different silicon connectivity beforehand [16,[21][22][23]. For the particular case of Silicalite-1 formation in presence of tetrapropylammonium cations (TPA ?…”

Section: Introductionmentioning

confidence: 99%

Multi-level Modeling of Silica–Template Interactions During Initial Stages of Zeolite Synthesis

et al. 2009

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Zeolite synthesis is driven by structure-directing agents, such as tetrapropyl ammonium ions (TPA ? ) for Silicalite-1 and ZSM-5. However, the guiding role of these organic templates in the complex assembly to highly ordered frameworks remains unclear, limiting the prospects for advanced material synthesis. In this work, both static ab initio and dynamic classical modeling techniques are employed to provide insight into the interactions between TPA ? and Silicalite-1 precursors. We find that as soon as the typical straight 10-ring channel of Silicalite-1 or ZSM-5 is formed from smaller oligomers, the TPA ? template is partially squeezed out of the resulting cavity. Partial retention of the template in the cavity is, however, indispensable to prevent collapse of the channel and subsequent hydrolysis.

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Section: Introductionmentioning

confidence: 99%

Multi-level Modeling of Silica–Template Interactions During Initial Stages of Zeolite Synthesis

et al. 2009

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“…[5][6][7] Optical microscopy and X-ray scattering techniques have been employed initially to understand the kinetics of crystal growth from clear solutions. [8,9] Observing the internal and surface structure of the exposed faces of crystals synthesised under various conditions provide an alternative route to understand growth mechanisms in these materials. This demands nanometer resolution techniques and, hence, high-resolution scanning electron microscopy (HRSEM), high-resolution transmission electron microscopy (HRTEM) and atomic force microscopy (AFM) have been employed in recent years.…”

Section: Introductionmentioning

confidence: 99%

Evolution of Surface Morphology with Introduction of Stacking Faults in Zeolites

John

Stevens

Terasaki

et al. 2010

Chemistry A European J

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This paper sets out to try to determine some of the nanoscopic details of template action in zeolites. The problem has been addressed by monitoring the effects of competitive templating using, in particular, atomic force microscopy and high-resolution scanning electron microscopy. Using these techniques, it is possible to determine the subtle crystal growth changes that occur as a result of altering the concentration of these competitive templating agents. This work concerns the two important intergrowth systems MFI-MEL and FAU-EMT. It was found that some organic templating agents provide much greater structure-directing specificity. So much so in the case of the MFI-MEL system that a 2 mol% doping with the highly specific tetrapropylammonium cation drastically changes the fundamental growth processes. Furthermore, the effect of template crowding is shown to reduce specificity. This work shows how extensive frustrated intergrowth structures can still be accommodated within a nominal zeolite single crystal.

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“…Typical molar composition space for silicalite-1 in the system SiO2-TPAOH-H2O occurring either in concentrated media (yellow area) as investigated by Corkery, van Santen, and Cundy et al [12,13,24,59], or dilute systems (blue area) as studied by Davis, Tsapatsis, and Shantz et al [3,22,27,28,41,42,50,51,60,61]. Both domains have also been extensively explored by Nikolakis, Lobo, and Martens et al [1,2,4,10,14,17,20,25,26,62].…”

Section: Introductionmentioning

confidence: 99%

“…Since their discovery in the mid 1990s many controversial studies have attempted to derive the exact status of the very early nanoparticles of small size in the range a few nanometers [2,3,[12][13][14][15][16][17][18][19][20][21]. The question of whether these nanoparticles contain occluded organic templates or are simply organic-free silica entities has been disputed [9] and a core-shell structure with a negatively charged surface silica core surrounded by a shell of organocations, might seem to be the most accepted description [1,2,10,15,[22][23][24][25][26][27][28][29][30]. Alternatively, at precursor formation before any heating, light diffusing nanoparticles have been demonstrated as aggregated oligomeric silicates, and not as dense silica particles [4].…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2016

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Abstract:The dynamic behavior of tetrapropylammonium (TPA) cations in the clear precursor sols for silicalite synthesis has been investigated by 1 H diffusion ordered spectroscopy (DOSY), T 1 , T 2 , and T 1ρ 1 H relaxation, as well as 1 HÑ 13 C 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 1 HÑ 13 C 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 T 2 and T 1ρH , as a consequence of involvement of these latter in ion-pairing interactions with water-solvated TPA molecules slowing down their mobility. Furthermore, from the 1 HÑ 13 C CP dynamics curve profiles a change in the CP transfer regime was observed from fast (T CH << T 1ρH ) for solutions without silicates to moderate (T CH~T1ρH ) when silicates are interacting with the TPA cations that may reflect the occlusion of TPA into flexible silicate hydrate aggregates.

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Combined in situ 29Si NMR and small-angle X-ray scattering study of precursors in MFI zeolite formation from silicic acid in TPAOH solutions

Cited by 67 publications

References 31 publications

Multi-level Modeling of Silica–Template Interactions During Initial Stages of Zeolite Synthesis

Multi-level Modeling of Silica–Template Interactions During Initial Stages of Zeolite Synthesis

Evolution of Surface Morphology with Introduction of Stacking Faults in Zeolites

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

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