Some observations on the preparation and properties of colloidal silicalites. Part I: synthesis of colloidal silicalite-1 and titanosilicalite-1 (TS-1)

Cundy, Colin S.; Forrest, James O.; Plaisted, R.J.

doi:10.1016/j.micromeso.2003.08.021

Cited by 107 publications

(88 citation statements)

References 56 publications

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“…First TEOS was hydrolyzed in 40 wt % TPAOH aqueous solution at ambient conditions under vigorous magnetic stirring for approximately 1 h. Appropriate amounts of water were then added subsequently when it was necessary. The compositions were chosen to be in the range of those used in silica precursor particle studies [14,25,61] and silicalite-1 growth experiments [59]. All samples were allowed to equilibrate for a minimum of three days before NMR measurement.…”

Section: H Dosy Nmrmentioning

confidence: 99%

“…These results are discussed in the general context of zeolite nucleation and crystal growth. 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: 98%

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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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Section: H Dosy Nmrmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

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

et al. 2016

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“…Nanozeolites are conveniently synthesized from monomeric silicon sources in the presence of high concentrations of an organic template. [14][15][16][17][18][19][20][21][22][23][24] The key for reducing the zeolite particle size limitation is to favor nucleation over crystal growth. This effect can sometimes be achieved by applying a special temperature profile during crystallization.…”

Section: Introductionmentioning

confidence: 99%

Formation of ZSM‐22 Zeolite Catalytic Particles by Fusion of Elementary Nanorods

Hayasaka

Liang

Huybrechts

et al. 2007

Chemistry A European J

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An ZSM-22 aluminosilicate zeolite was synthesized using the hydrothermal gel method at 150 degrees C. Products obtained after different synthesis times were characterized using various techniques and catalytic testing. Massive formation of ZSM-22 nanocrystals occurs after only a short synthesis time, appearing as isolated rods with a cross section of 12+/-4 nm. Nanorods have aluminum enriched at their external surface. Later in the crystallization process nanorods align and fuse sideways, whereby the external surface is systematically converted into an internal micropore surface. The formation of aluminum bearing micropores by the joining of nanorod surfaces is responsible for the enhanced catalytic activity. For this, the zeolite synthesis of nanoscale crystallites is ineffective for enhancing catalytic activity.

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“…This behavior is expected even with the first idea of the model of autocatalytic crystallization 12 and is completely in accordance with findings of Cundy et al, on synthesis of silicalite-1 and titanosilicalite-1. 13 Curves of the nucleation (maybe better expression is the curves of the nuclei appearance in the system, i.e. the time when they begin to grow) are shown in Figure 4, and used for the calculation of the nuclei distribution within gel matrix.…”

Section: Resultsmentioning

confidence: 99%

Zeolite A Synthesis under Dynamic Conditions, after Hydrogel Ageing

Palčić¹,

Sekovanić²,

Subotić³

et al. 2012

Croat. Chem. Acta

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Abstract. Zeolites are crystalline, microporous, alumo-silicate materials (around 400 types) which are used in many applications. Each field of usage (catalysis, ion exchange, sorption, molecular sieving, etc.) has demands regarding crystals' structural and particulate properties. Detailed understanding of the mechanisms of crystals' formation and growth enables the control of these properties. Hydrogels of the starting composition 3.2 Na 2 O × 2 SiO 2 × 1.05 Al 2 O 3 × 250 H 2 O were heated in stainless steel reactor at 80 °C under dynamic conditions, after ageing for t A = 0-209 h at 25 °C. Solid phase samples were characterized using microscopy (OM, SEM), PXRD and laser light scattering (LLS). Specific number of zeolite A crystals was calculated from particle size distributions. It was shown that the some particulate properties: specific number of crystals and crystal size distribution, are changing towards higher number of crystals and wider size distribution while the morphology of the crystals remains the same. Also, the crystal growth rate is higher in the systems which are treated under dynamic conditions. Obtained results were compared with data of systems crystallized under static conditions and commented on the grounds of the autocatalytic nucleation theory.

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Some observations on the preparation and properties of colloidal silicalites. Part I: synthesis of colloidal silicalite-1 and titanosilicalite-1 (TS-1)

Cited by 107 publications

References 56 publications

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

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

Formation of ZSM‐22 Zeolite Catalytic Particles by Fusion of Elementary Nanorods

Zeolite A Synthesis under Dynamic Conditions, after Hydrogel Ageing

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