Atomic arrangements in amorphous sodium titanosilicate precursor powders

Kostov‐Kytin, Vladislav; Mihailova, Boriana; Kalvachev, Yuri; Tarassov, Mihail

doi:10.1016/j.micromeso.2005.07.024

Cited by 28 publications

(17 citation statements)

References 28 publications

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“…The exfoliation and the band at lower displacement increases, which will have been generated from the exchange of Na + by protons as observed for nenadkevichite and ETS-4, [27] in agreement with other observations on AM-4 material. [28] This effect could also be attributed to the breaking of X-O-X bonds (X = Si and Ti), which is consistent with the fine, high length/width ratio particles observed by TEM. [19] Completing the spectroscopic analysis, Figure 9 shows the diffuse-reflectance ultraviolet/visible (DR-UV) absorption spectra of the samples.…”

Section: Samplesupporting

confidence: 78%

Synthesis, Swelling, and Exfoliation of Microporous Lamellar Titanosilicate AM‐4

et al. 2011

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AM‐4 is a layered porous titanosilicate built from TiO6 and SiO4 polyhedra. An improved synthesis of AM‐4 crystalsenabling control of particle size by secondary growth and reducing synthesis time is presented. A new material, UZAR‐S2, has been obtained by exfoliation of the smaller AM‐4. The exfoliation consists of proton exchange with acetic acid, intercalation with nonylamine, and final activation by washing with HCl/water/ethanol. Besides XRD, TEM, N2 adsorption, FTIR, and UV/Vis characterization highlighting the delaminated character of UZAR‐S2, CO2 adsorption was also measured.

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Section: Samplesupporting

confidence: 78%

Synthesis, Swelling, and Exfoliation of Microporous Lamellar Titanosilicate AM‐4

et al. 2011

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“…Likewise, bands near 764 and 706 cm )1 have been associated with Si-O stretching [88] though a d Si-O-Si vibration has also been assigned to 769 cm )1 Raman shift in certain aluminosilicates [90]. A band in the 910-940 cm )1 region that also appears in various calculations of spectra of a fully dissociated, Q 0 type orthogonal [SiO 4 ] 4) monomer ion [14,64] has been assigned to m as Si-O [14,64,88], d O-Si-O [88], and Q 3 type m Si-O-Si [75,79,87] vibrations. A Raman band near 600 cm )1 has been associated with m s Si-O-Si vibrations [14,20,29,32,72,79,88,101] and it is a known benchmark of planar 3-fold Si-O rings [14,72,77,[102][103][104][105] in various silicates.…”

Section: Raman Spectramentioning

confidence: 92%

“…For example vibrations near 1145 cm )1 are typically associated with 3D silica networks [18,36,69,72,[74][75][76][77][78]93] which cannot be the case in our metasilicates. In contrast, most investigators identify a Raman band near 975 cm )1 with a chain like Q 2 silicate structure [14,69,[75][76][77][78][86][87][88][89]91,92] like that of Na 2 SiO 3 ( figure 5, table 2). Likewise, bands near 764 and 706 cm )1 have been associated with Si-O stretching [88] though a d Si-O-Si vibration has also been assigned to 769 cm )1 Raman shift in certain aluminosilicates [90].…”

Section: Raman Spectramentioning

confidence: 99%

Vibrational spectra and dissociation of aqueous Na2SiO3 solutions

Halász¹,

Agarwal²,

Li³

et al. 2007

Catal Lett

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To facilitate molecular spectroscopic observation of the mysterious transition of dissolved sodium silicate molecules into nanoparticles of desired silica gel and zeolite structures, the IR and Raman spectra of Na 2 H 2 SiO 4 monomers are studied here in details. It is demonstrated that the 3-0.2 mol/L aqueous solutions of Na 2 SiO 3 and Na 2 SiO 3 Â 9H 2 O contain mostly Na 2 H 2 SiO 4 monomers dissociated about 30%-80%, respectively. In contrast to the common belief the Si-O vibrations of these monomers depend on their dissociation level generating FTIR and Raman bands which are frequently associated with polymer silica structures in the current literature. To stay consistent with the molweight and dissociation measurements, these vibrational assignments are revised in this paper. Some unique and unexpected effects of D 2 O used instead of H 2 O as solvent are also reported.

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“…Phase transitions are usually observed when ionic forms of alkali metals, such as Na and K, are incorporated during the synthesis of titanosilicates [13–16, 18]. In silica materials, it is well known that the presence of Group 1 elements (such as Na and Li) facilitate phase separations by significantly lowering the transition temperature [19] and similar effects are seen in titanosilicates.…”

Section: Introductionmentioning

confidence: 99%

Titanium(IV)-induced cristobalite formation in titanosilicates and its potential impact on catalysis

et al. 2018

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Cristobalite, a crystalline form of silica, is shown to be formed within an amorphous titanosilicate, at previously unknown conditions. Mesoporous titanosilicate microspheres (MTSM) were synthesized as efficient catalysts for the epoxidation of cyclohexene with tert-butyl hydroperoxide. High-resolution transmission electron microscopy revealed the presence of crystals in this predominantly amorphous material, after calcination at 750 °C. When calcined at 800 °C, the crystals were identified via PXRD as predominantly cristobalite, which possibly marks its first observation in titanosilicates at such a low temperature, without adding any alkali metals during synthesis. Catalytic experiments conducted with MTSM materials calcined at temperatures varying from 650 to 950 °C, reveal that the amount of cristobalite formed increases with temperature, and that it has a significant impact on the pore structure, and, remarkably, correlates with the catalytic activity of titanosilicates.Electronic supplementary materialThe online version of this article (10.1007/s10853-018-2869-0) contains supplementary material, which is available to authorized users.

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Atomic arrangements in amorphous sodium titanosilicate precursor powders

Cited by 28 publications

References 28 publications

Synthesis, Swelling, and Exfoliation of Microporous Lamellar Titanosilicate AM‐4

Synthesis, Swelling, and Exfoliation of Microporous Lamellar Titanosilicate AM‐4

Vibrational spectra and dissociation of aqueous Na2SiO3 solutions

Titanium(IV)-induced cristobalite formation in titanosilicates and its potential impact on catalysis

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