Simultaneous monitoring of amorphous and crystalline phases in silicalite precursor gels. An in situ hydrothermal and time-resolved small- and wide-angle X-ray scattering study

Dokter, WH Wim; Beelen, Tpm Theo; Garderen, van Hf; Santen, van Ra Rutger; Bras, Wim; Derbyshire, G. E.; Mant, GR

doi:10.1107/s0021889894004693

Cited by 44 publications

(20 citation statements)

References 8 publications

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“…In situ X-ray scattering measurements have been carried out using synchrotron radiation to observe the crystallization of microporous materials under hydrothermal heating conditions. [5][6][7][8][9][10] In situ studies such as these enable direct observation of the gel formation and dissolution, nucleation, and growth processes of zeolites.…”

Section: Introductionmentioning

confidence: 99%

In Situ SAXS/WAXS of Zeolite Microwave Synthesis: NaY, NaA, and Beta Zeolites

et al. 2007

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A custom waveguide apparatus is constructed to study the microwave synthesis of zeolites by in situ small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS). The WR-284 waveguide is used to heat precursor solutions using microwaves at a frequency of 2.45 GHz. The reaction vessels are designed to include sections of thin-walled glass, which permit X-rays to pass through the precursor solutions with minimal attenuation. Slots were machined into the waveguide to provide windows for X-ray energy to enter and scatter from solutions during microwave heating. The synthesis of zeolites with conventional heating is also studied using X-ray scattering in the same reactor. SAXS studies show that the crystallization of beta zeolite and NaY zeolite is preceded by a reorganization of nanosized particles in their precursor solutions or gels. The evolution of these particles during the nucleation and crystallization stages of zeolite formation depends on the properties of the precursor solution. The synthesis of NaA and NaX zeolites and sodalite from a single zeolite precursor is studied by microwave and conventional heating. Microwave heating shifts the selectivity of this synthesis in favor of NaA and NaX over sodalite; conventional heating leads to the formation of sodalite for synthesis from the same precursor. The use of microwave heating also led to a more rapid onset of NaA zeolite product crystallization compared to conventional heating. Pulsed and continuous microwave heating are compared for zeolite synthesis. The resulting rates of formation of the zeolite products, and the relative amounts of the products determined from the WAXS spectra, are similar when either pulsed or continuous microwave heating is applied in the reactor while maintaining the same synthesis temperature. The consequences of these results in terms of zeolite synthesis are discussed.

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Section: Introductionmentioning

confidence: 99%

In Situ SAXS/WAXS of Zeolite Microwave Synthesis: NaY, NaA, and Beta Zeolites

et al. 2007

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“…Aging of wet silica gels was carried out at room temperature [8]. Silicalite was prepared according to both heterogeneous [9] and homogeneous [lo] preparation recipes.…”

Section: Methodsmentioning

confidence: 99%

“…Because the Si-0-Si angle can be very easily varied between 90" and 150", 3, 4, 5 or higher membered rings can also be formed, being precursors for three-dimensional structures [9].…”

Section: Polymerization and Aggregation Of Silicamentioning

confidence: 99%

“…This aim has been achieved with the recently developed SAXS-WAXS technique 1131. To obtain information concerning the nature of the precursor gel and whether nucleation occurs within the gel or from the mother liquid of the synthesis mixture, silicalite was prepared both heterogeneously from a gel [9] and homogeneously starting from solution [IO]. Although reaction conditions were different (190°C and 12O"C, respectively, and slightly different reaction mixtures), SAXS-WAXS spectra were very similar and are shown in Figs.…”

Section: $'Saxs-waxs Investigations On Silicalitementioning

confidence: 99%

See 1 more Smart Citation

Aggregation and aging in silica gel

Santen

Beelen

Garderen

et al. 1995

Nuclear Instruments and Methods in Physics Research Section B:

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“…Synchrotron radiation sources have enhanced the power of the technique in many different respects, more notably in permitting the study of the time evolution of complex structures [2].…”

Section: Introductionmentioning

confidence: 99%