Packing Effects in the Liquid-Phase Adsorption of C5-C22 n-Alkanes on ZSM-5

Meyer, Kurt M. A. De; Chempath, Shaji; Denayer, Joeri; Martens, Johan A.; Snurr, Randall Q.; Baron, Gino V.

doi:10.1021/jp0354144

Cited by 52 publications

(63 citation statements)

References 29 publications

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“…Calero et al 28,29 and Krishna et al [30][31][32][33] investigated the subtle entropy effects in the adsorption of multicomponent mixtures of linear and branched alkanes, and demonstrated the development of separation processes. De Meyer et al 34 and Chempath et al 35 presented simulations of the liquid-phase adsorption of linear alkanes and their mixtures on ZSM-5 and silicalite, and good agreement with experimental results was obtained. Düren and Snurr 36 computed the adsorption of C 1 and nC 4 and their mixtures on isoreticular metal-organic frameworks, and the influence of the organic linker molecule on adsorption and selectivity were analyzed.…”

Section: Introductionmentioning

confidence: 78%

“…There are two kinds of energetically favorable adsorption sites within the bundle, the nanotube interiors and the interstitial channels between the nanotubes. The van der Waals gap g between nanotubes was initially set to 3.2 Å, 33,34 and later in order to examine adsorption in the interstitial channels, g = 4.2 Å was also used. Each ͑10, 10͒ SWNT within the bundle has a diameter of 13.56 Å, and the carbon atoms were assumed to be rigid and frozen during simulation.…”

Section: Model and Potentialmentioning

confidence: 99%

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Adsorption and separation of linear and branched alkanes on carbon nanotube bundles from configurational-bias Monte Carlo simulation

et al. 2005

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The adsorption and separation of linear ͑C 1 -nC 5 ͒ and branched ͑C 5 isomers͒ alkanes on single-walled carbon nanotube bundles at 300 K have been studied using configurational-bias Monte Carlo simulation. For pure linear alkanes, the limiting adsorption properties at zero coverage exhibit a linear relation with the alkane carbon number; the long alkane is more adsorbed at low pressures, but the reverse is found for the short alkane at high pressures. For pure branched alkanes, the linear isomer adsorbs to a greater extent than its branched counterpart. For a five-component mixture of C 1 -nC 5 linear alkanes, the long alkane adsorption first increases and then decreases with increasing pressure, but the short alkane adsorption continues increasing and progressively replaces the long alkane at high pressures due to the size entropy effect. All the linear alkanes adsorb into the internal annular sites with preferred alignment parallel to the nanotube axis on a bundle with a gap of 3.2 Å, and also intercalate the interstitial channels in a bundle with a gap of 4.2 Å. For a three-component mixture of C 5 isomers, the adsorption of each isomer increases with increasing pressure until saturation, though nC 5 increases more rapidly with pressure and is preferentially adsorbed due to the configurational entropy effect. All the C 5 isomers adsorb into the internal annular sites on a bundle with a gap of 3.2 Å, but only nC 5 also intercalates the interstitial channels on a bundle with a gap of 4.2 Å. This work suggests the possibility of separating alkane mixtures based on differences in either size or configuration, as a consequence of competitive adsorption on the carbon nanotube bundles.

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Section: Introductionmentioning

confidence: 78%

Section: Model and Potentialmentioning

confidence: 99%

Adsorption and separation of linear and branched alkanes on carbon nanotube bundles from configurational-bias Monte Carlo simulation

et al. 2005

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“…The importance of entropy effects in the adsorption of alkanes on ZSM-5 has been demonstrated by computational techniques [34][35][36]. Also in liquid phase, remarkable chain length dependent adsorption effects have been observed on ZSM-5 [37][38][39]. Figure 7 shows the adsorption saturation capacity of the C 5 -C 22 n-alkanes, expressed in number of molecules and total number of -CH x groups adsorbed per unit cell.…”

Section: Chain Length Induced Selectivity Reversal In Zsm-5mentioning

confidence: 95%

“…For molecules shorter than C 14 , it appears that the available space in the pores of ZSM-5 is thus not completely used, and gaps must be present between the adsorbed molecules. A calculation of the total occupied length of the adsorbed n-alkane molecules (taking into account the repulsion between -CH x groups from neighbouring molecules) shows the same tendency [38]. The packing mechanisms of the n-alkanes were studied by configurational-bias GCMC calculations [39].…”

Section: Chain Length Induced Selectivity Reversal In Zsm-5mentioning

confidence: 97%

Adsorption and Reaction in Confined Spaces

Denayer¹,

Daems²,

Baron³

2006

Oil & Gas Science and Technology - Rev. IFP

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Résumé -Adsorption et réaction dans des espaces confinés -L'adsorption de molécules dans des matériaux microporeux cristallins implique des interactions énergétiques et entropiques spécifiques. L'assemblage moléculaire dans ces espaces confinés résulte dans des effets de sélectivité complètement différents des ceux qu'on observe traditionnellement avec des solides amorphes ou mésoporeux. Quelques exemples d'effets entropiques ou d'assemblage moléculaire dans l'adsorption d'hydrocarbures dans des zéolites sont présentés. Abstract -Adsorption and Reaction in Confined Spaces

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“…The value of O-CH x also has an effect on the maximum loading and packing efficiency. De Meyer et al [25] performed experiments of long chain n-alkanes in silicalite. Experiments show that the maximum packing is approximately 53.2 carbon atoms per unit cell for n-C 14 , while the current model yields 52.5 carbon atoms per unit cell in excellent agreement with experiment.…”

Section: Volume 93 Number 8 P H Y S I C a L R E V I E W L E T T E R mentioning

confidence: 99%

Force Field Parametrization through Fitting on Inflection Points in Isotherms

et al. 2004

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We present a method to determine potential parameters in molecular simulations of confined systems through fitting on experimental isotherms with inflection points. The procedure uniquely determines the adsorbent-adsorbate interaction parameters and is very sensitive to the size parameter. The inflection points in the isotherms are often related to a subtle interplay between different adsorption sites. If a force field can predict this interplay, it also reproduces the remaining part of the isotherm correctly, i.e., the Henry coefficients and saturation loadings. DOI: 10.1103/PhysRevLett.93.088302 PACS numbers: 82.75.Jn, 47.55.Mh, 66.30.-h The effect of confinement on adsorption and diffusion is still poorly understood despite its importance for practical applications. The performance of molecular sieves in separation and catalytic processes depends critically on the match between sieve topology and the shape and size of the adsorbate [1]. It is therefore of considerable industrial importance to explore the adsorption and diffusion of linear and branched alkanes in different topologies using realistic simulations at the microscopic level [2]. Different parameter sets yield values of diffusivities that differ not only quantitatively but also show a different qualitative dependence on the molecular loading [3]. The critical unresolved question follows: Which of these parameter sets is the most physically realistic one? Here, we hope to remedy this situation.Potential parameter sets can be checked only via comparison with experiment. For diffusion the comparison is complicated by large discrepancies between microscopic and macroscopic experimental measurement methods, and even within the same measurement technique there are many disagreements between various studies. However, adsorption results seem to be well established and provide a more solid basis for a detailed comparison between experiment and simulation. Moreover, a large amount of data exists on adsorption of hydrocarbons in siliceous zeolites.Silicalite-1 (Fig. 1) consists of a three-dimensional pore system with straight parallel channels, intersected by zigzag channels [4]. The channels of approximately 6 Å in diameter lead to shape selectivity, especially for the isomers of hexane, which have dimensions close to the silicalite-1 pores. The linear channels intersect with the zigzag channels 4 times per unit cell. Interestingly, for n-heptane and for the branched alkanes in silicalite-1 a kink in the isotherm is observed [5]. This inflection is directly related to the number of intersections in the structure and occurs at exactly four molecules per unit cell. As these inflections are caused by a subtle interplay between the size and configuration of the molecule and two different adsorption sites, it becomes clear that the adsorbent-adsorbate potential size parameter is the most sensitive parameter in the force field.In general, adsorption in any periodic structure has steps or kinks. The reason is that steps and kinks signal transitions between diffe...

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Packing Effects in the Liquid-Phase Adsorption of C₅_-C₂₂ n-Alkanes on ZSM-5

Cited by 52 publications

References 29 publications

Adsorption and separation of linear and branched alkanes on carbon nanotube bundles from configurational-bias Monte Carlo simulation

Adsorption and separation of linear and branched alkanes on carbon nanotube bundles from configurational-bias Monte Carlo simulation

Adsorption and Reaction in Confined Spaces

Force Field Parametrization through Fitting on Inflection Points in Isotherms

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