Adsorption properties of lamellar silica

Kuznetsov, Boris; Lanin, S. N.; Rakhmanova, T. A.; Смирнов, В. В.; Цодиков, М. В.; Tarasova, D. V.

doi:10.1134/s0036024407050238

Cited by 8 publications

(17 citation statements)

References 7 publications

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“…Similarly, the heats of adsorption at infinite dilution at 298 K for all three water models were close to each other: 33.2, 31.0, and 29.7 kJ/mol for the SPC, MSPC/E, and SPC/exp-6 models, respectively, which are all in good agreement with various experimental work ,,,, and with the value of 32.5 kJ/mol calculated by Demontis et al However, when the vapor-phase adsorption isotherms at 298 K were calculated for the three water models, it was seen that water−water−silicalite three-body interactions had a significant impact on the accuracy of the simulations. Isotherms for the three different models are shown in Figure , in comparison with the previous experimental data ,− that exhibit significant variations due to the differences in samples used, where the effects of various defects, their distribution, and their crystal size are significant. The steep water uptake in experimental isotherms may be attributed to capillary condensation occurring in the mesoporosity or macroporosity of the zeolite sample .…”

Section: Resultsmentioning

confidence: 82%

“…Silicalite-1, which is an all-silica version of MFI-type zeolite ZSM-5, is especially suitable for some possible environmental applications of the removal and/or remediation of organics, such as chlorinated VOCs , and MTBE , in water. Consequently, the behavior of water confined within silicalite-1 has become a subject of great scientific and technological interest. ,− However, there is not much agreement among these studies, which may be attributed to the differences in samples used in these experiments, where the effects of various defects, their distribution, and crystal size are significant. A typical example is the work of Oumi et al, where the authors obtained two different isotherms depending on whether the crystals were prepared in the presence of HF.…”

Section: Introductionmentioning

confidence: 99%

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Monte Carlo Simulation of Water Adsorption in Hydrophobic MFI Zeolites with Hydrophilic Sites

Ahunbay

2011

Langmuir

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The effect of strong and weak hydrophilic sites, Al atoms with associated extraframework Na cations and silanol nests, respectively, in high-silica MFI zeolites on water adsorption was investigated using Monte Carlo simulations. For this purpose, a new empirical model to represent potential energy interactions between water molecules and the MFI framework was developed, which reproduced the hydrophobic characteristics of a siliceous MFI-type zeolite, silicalite-1, with both the vapor-phase adsorption isotherm and heats of adsorption at 298 K being in good agreement with experimental data. The proposed model is also compatible with previous hydrocarbon potential models and can be used in the adsorption simulations of VOC-water mixtures. Adsorption simulations revealed that strongly hydrophilic Al sites in Na-ZSM-5 zeolites coordinate two water molecules per site at low coverage, which promotes water clustering in the vicinity of these sites. However, weakly hydrophilic silanol nests in silicalite-1 are in coordination with a single water molecule per site, which does not affect the adsorption capacity significantly as expected. However, even in the presence of 0.125 silanol nest per unit cell, the increase in the heat of adsorption at low coverage is drastic.

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Section: Resultsmentioning

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Monte Carlo Simulation of Water Adsorption in Hydrophobic MFI Zeolites with Hydrophilic Sites

Ahunbay

2011

Langmuir

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“…Its solution is largely due to the choice of grid parameters. The procedure of the grid parameters choosing is the same as for thermal diffusivity phase [13] and chemical conversions [14].…”

Section: Mathematical Model and Solution Methodsmentioning

confidence: 99%

“…However, the procedures [13,14] are used for values of the heat flux less then 10 5 W/ m2 and large heating time.…”

Section: Mathematical Model and Solution Methodsmentioning

confidence: 99%

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The errors when determining the thermophysical characteristics of liquids by the laser flash method

Katz

2016

MATEC Web Conf.

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The analysis of errors in determining the thermophysical characteristics of typical organic liquids, specified by conductive-radiative heat transfer of ultrathin heated up to high temperature sample layer, under conditions consistent with the implementation of the laser pulse method, when exposed to the surface of the collimated laser pulse of finite duration was made. The influence to the error of the radiation absorption process was discovered.

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Catalytic conversions of chloroolefines over iron oxide nanoparticles 3. Electronic and magnetic properties of γ-Fe2O3 nanoparticles immobilized on different silicas

et al. 2006

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Catalytic properties of superparamagnetic γ ferric oxide nanoclusters, which are uniform in terms of size and magnetic properties were studied. The catalysts were supported on the activated silica gel matrix (AGM) prepared from the KSK 2 silica gel of globular structure and on the activated silica matrix (ASM) prepared from layered natural vermiculite. The clusters are active in some reactions of chloroolefin conversions: isomerization of dichlorobutenes and alkylation of benzene with allyl chloride. Their activity in these reactions is many times higher that of usual suppоrted catalysts based on α ferric oxide. Analysis of the Mössbauer spectra of the 2.5 wt.% Fe/AGM and 2.5 wt.%Fe/ASM samples before and after the reaction at Т = 3-300 К shows that during the reaction some Fe III ions arranged in ∼2-3 nm γ Fe 2 O 3 nanoclusters magnetically ordered at 6 K are reduced to form a high spin Fe II complex in the paramagnetic state. According to the macroscopic magnetization data (SQUID) of the initial clusters, curves with hysteresis are observed at 2 K in the plots of forward and backward magnetization, while the 2.5 wt.%Fe/ASM catalyst after the reaction at Т = 2 К demonstrates a linear field dependence of the magnetization passing through the coordinate origin. Analysis of the Mössbauer spectra and magnetic properties suggests that during the catalytic reaction the Fe III ions in the γ Fe 2 O 3 nanoclusters interact with chloroolefin with the allylic structure to be partially reduced to the Fe II ions that are bound in a complex containing chloride ions and O II ion(s) of the silicate matrix as ligands. This is a reason, probably, for the high catalytic activity of γ Fe 2 O 3 nanoparticles.

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Adsorption properties of lamellar silica

Cited by 8 publications

References 7 publications

Monte Carlo Simulation of Water Adsorption in Hydrophobic MFI Zeolites with Hydrophilic Sites

Monte Carlo Simulation of Water Adsorption in Hydrophobic MFI Zeolites with Hydrophilic Sites

The errors when determining the thermophysical characteristics of liquids by the laser flash method

Catalytic conversions of chloroolefines over iron oxide nanoparticles 3. Electronic and magnetic properties of γ-Fe2O3 nanoparticles immobilized on different silicas

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