Zeolites X and A crystallization compared by simultaneous UV/VIS-Raman and X-ray diffraction

Depla, Anouschka; Verheyen, Elke; Veyfeyken, An; Gobechiya, Elena; Hartmann, Thomas; Schaefer, Reinhold; Martens, Johan A.; Kirschhock, Christine

doi:10.1039/c1cp20157c

Cited by 42 publications

(33 citation statements)

References 71 publications

(173 reference statements)

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“…They are identical to the Raman signatures of the LSX framework [38]. The new band at 723 cm -1 is due to the symmetric T-O stretches [38]. The intensities of the bands at 1024 and 1060 cm -1 decreased a lot and two new bands at 951 and 982 cm -1 appeared, all of which are assigned to the asymmetric T-O stretches of TO 4 units [49].…”

Section: Resultsmentioning

confidence: 64%

“…Upon heating the gel for 3.5 h or longer, the Raman bands remained unchanged. They are identical to the Raman signatures of the LSX framework [38]. The new band at 723 cm -1 is due to the symmetric T-O stretches [38].…”

Section: Resultsmentioning

confidence: 65%

“…The band at 460 cm -1 results from the deformation of the T-O-T angle of 4Rs adjacent to K ? ions [38]. These changes indicate that sodalite cages were connected via D6Rs to form crystalline LSX zeolite.…”

Section: Resultsmentioning

confidence: 95%

“…They proposed that the crystalline zeolite X framework was formed via the assembly of four-membered rings (4Rs) and 4R branched derivatives in the solid phase and monomeric silicate species in the liquid phase. Later Depla et al [38] carried out in situ studies of the crystallization of LSX zeolite by simultaneous UV Raman and X-ray diffraction (XRD) measurements. They pointed out the existence of 4Rs and 6Rs in the amorphous gel at an early stage of crystallization.…”

Section: Introductionmentioning

confidence: 99%

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An investigation into the crystallization of low-silica X zeolite

Zhang

Huang

2015

J Porous Mater

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The crystallization of low-silica X (LSX) zeolite with FAU topology was examined under hydrothermal synthesis conditions. PXRD was employed to follow the evolution of the long-range ordering of the gel. Raman spectra provided information on various ring and cage species existing in the gel. 27 Al and 29 Si solid-state NMR spectroscopy was utilized to monitor the change in local environment of tetrahedral sites. The results indicate that an amorphous aluminosilicate phase was formed immediately upon mixing different reactive species. Hydrothermal treatment led to the formation of sodalite-cage like species and the species with larger cavities, joint four-member rings (4Rs) and branched 4Rs, which are the structural building units of the FAU framework. These units were assembled into the crystalline structure of LSX zeolite. 23 Na and 39 K solid-state NMR results show that the transformation process was accompanied by the changes of the local structure of hydrated Na ? and K ? ions. The two types of cations may work synergistically to template the crystallization of LSX zeolite.

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Section: Resultsmentioning

confidence: 64%

Section: Resultsmentioning

confidence: 65%

Section: Resultsmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

An investigation into the crystallization of low-silica X zeolite

Zhang

Huang

2015

J Porous Mater

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“…Among the most widely used techniques for monitoring of LTA synthesis DLS, SAXS and Raman spectroscopy stand out. [12][13][14][15] In situ reaction monitoring is one of the foundations of the process analytical technology (PAT), which consists of the use of analyzers with rapid detection and low sample preparation for chemical and physical analysis during the process stream. [16][17][18] The implementation of PAT tools provides several advantages to the crystallization process, such as understanding the mechanism involved in the process and decreasing its failure chances; nding the end point of the reaction and decreasing the batching time, thus increasing the process efficiency; controlling the particle size of the product with high precision; and knowing, in real-time, the reaction progress in order to correct or stop the batch if the process is out of control.…”

Section: Introductionmentioning

confidence: 99%

Monitoring of the crystallization of zeolite LTA using Raman and chemometric tools

Chaves

Soares

Cardoso

et al. 2015

Analyst

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LTA zeolite is used both in industry as well as in laboratories, because of its spatial-specific structure which is useful in gas adsorption and in ion exchange separation. At-line reaction monitoring and multivariate analysis of data, such as Principal Component Analysis (PCA), are fundamentals of the Process Analytical Technology (PAT), which consists of the use of analyzers with rapid detection and low sample preparation for analysis during the process stream. In this work, an optimization of zeolite LTA synthesis was performed aiming to obtain nanocrystals and the synthesis was monitored using Raman spectroscopy and PCA. A reaction mixture of 6.2Na2O : Al2O3 : 2SiO2 : 128H2O was used and it was possible to obtain a small particle size and high crystallinity after 72 h of synthesis at 25 °C. The synthesis was monitored at-line, using Raman spectroscopy in both liquid and solid phases. The extension of the reaction could be clearly observed by the PCA scores. As expected, the liquid phase presented changes over time, but the solid phase presented three specific stationary conditions at 0-24 h, 32-56 h and 72-80, related to the beginning of the reaction, the nucleation process, and the crystal formation, respectively. In addition, it was possible to identify the intermediates of the reaction and with the aid of PCA to monitor the reaction close to the real time.

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Zeolite Beta Formation from Clear Sols: Silicate Speciation, Particle Formation and Crystallization Monitored by Complementary Analysis Methods

Castro

Haouas

Lim

et al. 2016

Chemistry A European J

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The formation of silicate nanoaggregates (NAs) at the very early stages of precursor sols and zeolite beta crystallization from silicate nanoparticles (NPs) are investigated in detail using a combination of different analysis methods, including liquid-state Si, Al, N, and H NMR spectroscopy, mass spectrometry (MS), small-angle X-ray scattering (SAXS), X-ray diffraction (XRD), and transmission electron microscopy at cryogenic temperatures (cryo-TEM). Prior to hydrothermal treatment, silicate NAs are observed if the Si/OH ratio in the reaction mixture is greater than 1. Condensation of oligomers within the NAs then generates NPs. Aluminum doped into the synthesis mixtures is located exclusively in the NPs, and is found exclusively in a state that is fourfold connected to silicate, favoring their condensation and aggregation. These results are in agreement with general trends observed for other systems. Silicate NAs are essential intermediates for zeolite formation and are generated by the aggregation of hydrated oligomers, aluminate, and templating cations. Subsequent further intra-nanoaggregate silicate condensation results in the formation of NPs. H and N liquid NMR as well as diffusion ordered spectroscopy (DOSY) experiments provide evidence for weakly restricted rotational and translational mobility of the organic template within NAs as a consequence of specific silicate-template interactions. NAs thus appear as key species in clear sols, and their presence in the precursor sol favors silicate condensation and further crystallization, promoted either by increasing the Si/OH ratio or by heating.

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Zeolites X and A crystallization compared by simultaneous UV/VIS-Raman and X-ray diffraction

Cited by 42 publications

References 71 publications

An investigation into the crystallization of low-silica X zeolite

An investigation into the crystallization of low-silica X zeolite

Monitoring of the crystallization of zeolite LTA using Raman and chemometric tools

Zeolite Beta Formation from Clear Sols: Silicate Speciation, Particle Formation and Crystallization Monitored by Complementary Analysis Methods

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