Sorption of hydrocarbons in silicalite-1 studied by intelligent gravimetry

Ban, Hongyan; Gui, Jianzhou; Duan, Linhai; Zhang, Xiaolin; Song, Lijuan; Sun, Zhaolin

doi:10.1016/j.fluid.2005.03.024

Cited by 13 publications

(10 citation statements)

References 28 publications

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“…17 (a) Snapshot showing the location of benzene molecules at the intersections of MFI. (b) CBMC simulations of the pure component isotherms for iC4, 2MP, 22DMB, benzene and nC7 in MFI at 300 K. (c, d) Experimental data for the M-S diffusivity, Ð i , of (c) iC4, 70 and (d) benzene 94 compared with the inverse thermodynamic factor 1/G i . Note that the data of Ban et al 94 for benzene were reported for the Fick diffusivity; these data were corrected to obtain the M-S Ð i .…”

Section: Influence Of 1/c I On the Loading Dependence Of Diffusivitiesmentioning

confidence: 99%

“…For example, Fig. 17 (c, d) Experimental data for the M-S diffusivity, Ð i , of (c) iC4, 70 and (d) benzene 94 compared with the inverse thermodynamic factor 1/G i . Note that the data of Ban et al 94 for benzene were reported for the Fick diffusivity; these data were corrected to obtain the M-S Ð i .…”

Section: Influence Of 1/c I On the Loading Dependence Of Diffusivitiesmentioning

confidence: 99%

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Influence of adsorption thermodynamics on guest diffusivities in nanoporous crystalline materials

Krishna

Baten

2013

Phys. Chem. Chem. Phys.

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Published experimental data, underpinned by molecular simulations, are used to highlight the strong influence of adsorption thermodynamics on diffusivities of guest molecules inside ordered nanoporous crystalline materials such as zeolites, metal-organic frameworks (MOFs), and zeolitic imidazolate frameworks (ZIFs). For cage-type structures (e.g. LTA, CHA, DDR, and ZIF-8), the variation of the free energy barrier for inter-cage hopping across the narrow windows, ÀdF i , provides a rationalization of the observed strong influence of pore concentrations, c i , on diffusivities. In open structures with large pore volumes (e.g. FAU, IRMOF-1, CuBTC) and within channels (MFI, BEA, MgMOF-74, MIL-47, MIL-53), the pore concentration (c i) dependence of the self-(D i,self), Maxwell-Stefan (Ð i), and Fick (D i) diffusivities are often strongly dictated by the inverse thermodynamic correction factor, 1/G i qln c i /qln p i ; the magnitudes of the diffusivities are dictated by the binding energies for adsorption. For many guesthost combinations Ð i Àc i dependence is directly related to the 1/G i vs. c i variation. When molecular clustering occurs, we get 1/G i > 1, causing unusual Ð i vs. c i dependencies. The match, or mis-match, between the periodicity of the pore landscape and the conformations of adsorbed chain molecules often leads to non-monotonic variation of diffusivities with chain lengths.

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Section: Influence Of 1/c I On the Loading Dependence Of Diffusivitiesmentioning

confidence: 99%

Section: Influence Of 1/c I On the Loading Dependence Of Diffusivitiesmentioning

confidence: 99%

Influence of adsorption thermodynamics on guest diffusivities in nanoporous crystalline materials

Krishna

Baten

2013

Phys. Chem. Chem. Phys.

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“…Intracrystalline diffusion parameters(Wu et al 1983;Ban et al 2005;Xiao and Wei 1992;Chon and Park 1988;Cavalcante and Ruthven 1995b) …”

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confidence: 99%

Diffusion in zeolites: is surface resistance a critical parameter?

et al. 2010

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Gravimetric uptake measurements were performed with cyclohexane for different Silicalite-1 crystals sizes. It was observed that the apparent diffusion coefficients vary with crystal size, confirming the existence of a surface resistance. Considering that surface and the intracrystalline characteristic diffusion times are additives, it was possible to dissociate the two resistances.Surface mass transfer coefficient was found to be in the same order of magnitude for the different samples and activated with temperature. The contribution of surface resistance to mass transfer limitation is lower at high temperatures and for the bigger crystals. Surface resistance is far from being negligible for the smaller crystals: for crystals of 2 µm, surface resistance represents more than 60% of the total mass transfer resistance at 398 K. And crystals of that size (in the order of 2 µm) are usually used industrially, in order to minimize mass transfer resistance.The surface of one of our sample was purified by etching with a solution of hydrogen fluoride, without any enhancement of the adsorption kinetic. Surface resistance may not be located at the extreme surface of the crystals but in a layer of non negligible thickness of distorted crystal structure around the crystals.

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“…o -Xylene is located exclusively in the intersections of the channels at 273 and 315 K . Several experimental studies that describe the adsorption of aromatics in MFI-type zeolites can be found in the literature. ,,,− …”

Section: Introductionmentioning

confidence: 99%

Adsorption of Aromatics in MFI-Type Zeolites: Experiments and Framework Flexibility in Monte Carlo Simulations

et al. 2020

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Computer simulations of adsorption of aromatics in zeolites are typically performed using rigid zeolite frameworks. However, adsorption isotherms for aromatics are very sensitive to small differences in the atomic positions of the zeolite (Chem. Phys. Lett., 1999, 308, 155−159). This article studies the effect of framework flexibility on the adsorption of aromatics in MFI-type zeolites computed by grand-canonical Monte Carlo simulations. New experimental data of adsorption of ethylbenzene in a MFItype zeolite at 353 K is presented. The adsorption of n-heptane, ethylbenzene, and xylene isomers is computed in three MFI-type zeolite structures. It is observed that the intraframework interactions in flexible framework models induce small but important changes in the atom positions of the zeolite and hence in the adsorption isotherms. Framework flexibility is differently "rigid": flexible force fields produce a zeolite structure that vibrates around a new equilibrium configuration with limited capacity to accommodate to a bulky guest molecule. The vibration of the zeolite atoms only plays a role at high loadings, and the adsorption is mainly dependent on the average positions of the atoms. The simulations show that models for framework flexibility should not be blindly applied to zeolites and a general reconsideration of the parametrization schemes for such models is needed.

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Sorption of hydrocarbons in silicalite-1 studied by intelligent gravimetry

Cited by 13 publications

References 28 publications

Influence of adsorption thermodynamics on guest diffusivities in nanoporous crystalline materials

Influence of adsorption thermodynamics on guest diffusivities in nanoporous crystalline materials

Diffusion in zeolites: is surface resistance a critical parameter?

Adsorption of Aromatics in MFI-Type Zeolites: Experiments and Framework Flexibility in Monte Carlo Simulations

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