Adsorption and Coadsorption of 2-methylpentane and 2,2-dimethylbutane in a ZSM-5 Zeolite

Bellat, Jean‐Pierre; Lemaire, Elina; Simon, Jean-Marc; Weber, Guy; Dubreuil, Anne-Claire

doi:10.1007/s10450-005-5907-6

Cited by 10 publications

(12 citation statements)

References 11 publications

(19 reference statements)

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“…This effect is not observed for the following cycles because adsorption occurs directly after desorption, when the sample is being cooled from high temperatures. A very similar increase on the adsorbed amount of 22DMB during the first heating between 343 and 433 K was reported by Bellat et al…”

Section: Resultssupporting

confidence: 86%

“…100 times greater for the linear molecule and almost independent of the loading. In a subsequent isobaric study by Bellat et al, an unexpected increase of the adsorbed amount of 22DMB during the heating of the sample from 343 to 443 K for the first time was observed. This phenomenon was ascribed to the phase transition from monoclinic to orthorhombic MFI structure.…”

Section: Introductionmentioning

confidence: 79%

“…In our previous work, 10 we proved that the other structures do not affect hydrocarbon adsorption, which is consistent with other works. 23,24 We performed grand-canonical Monte Carlo simulations to calculate the adsorption isobars with RASPA software. 40 We used values of pressures matching the experimental values and temperatures ranging from 173 to 573 K with 20 K intervals.…”

Section: ■ Molecular Simulationsmentioning

confidence: 99%

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Quasi-Equilibrated Thermodesorption Combined with Molecular Simulation for Adsorption and Separation of Hexane Isomers in Zeolites MFI and MEL

et al. 2017

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Adsorption of hexane isomers in high silica MFI and MEL zeolites was studied by means of quasi-equilibrated temperature-programmed desorption and adsorption and Monte Carlo simulations. Configurational bias and continuous fractional component Monte Carlo were applied for these systems, and their efficiency and effectiveness were compared. All branched hexane isomers, i.e., 2-methylpentane, 3-methylpentane, 2,3-dimethylbutane, and 2,2-dimethylbutane, were used. The agreement between experimental and calculated adsorption isobars confirmed that quasi-equilibrated temperature-programmed desorption and adsorption is an effective method for studying adsorption of branched alkanes in zeolites. Detailed literature review on adsorption of branched paraffins in MFI revealed diffusion limitations which make reaching adsorption equilibria of these molecules difficult with isothermal approach at low temperatures. Temperature-dependent measurements conducted in this work largely allowed avoiding such limitations. Adsorption equilibria of branched alkanes in MEL zeolite have been studied experimentally for the first time. Detailed analysis of the adsorption behavior of these systems revealed the presence of two adsorption sites located in the different intersections of the straight channels characteristic of the MEL framework. Molecular simulations for adsorption of mixtures of branched hexane isomers showed potential application of the MFI and MEL zeolites in separation of mono- and dibranched isomers.

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Section: Resultssupporting

confidence: 86%

Section: Introductionmentioning

confidence: 79%

Section: ■ Molecular Simulationsmentioning

confidence: 99%

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Quasi-Equilibrated Thermodesorption Combined with Molecular Simulation for Adsorption and Separation of Hexane Isomers in Zeolites MFI and MEL

et al. 2017

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“…Arik et al 2003), but the adsorption of branched hexane isomers has received far less attention (Gener et al 2002;Cavalcante and Ruthven 1995;Yang and Rees 1997;Stach et al 1986, Zhu et al 2001a, 2001bDenayer et al 1998;Bellat et al 2005). The hexane adsorption isotherm exhibits a step at a loading around 4 molecules per unit cell; the reason for this is the two different sites available to hexane molecules within the MFI structure, the channels and the intersections.…”

Section: Introductionmentioning

confidence: 97%

Can alkane isomers be separated? Adsorption equilibrium and kinetic data for hexane isomers and their binary mixtures on MFI

Ferreira

Mittelmeijer‐Hazeleger

Bliek

2007

Adsorption

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In this study we present a global overview of the adsorption behavior of hexane isomers on MFI. With an experimental approach that couples a manometric technique with Near Infrared (NIR) spectroscopy, which has been recently developed, we did address adsorption kinetic properties of n-hexane, 2-methylpentane, 2,2-dimethylbutane and 2,3-dimethylbutane, and their binary mixtures. The adsorption equilibrium properties of the binary mixtures were also assessed using the same technique. Whereas the adsorption isotherms and heats of adsorption for single components have been studied by a manometric technique coupled with a micro calorimeter. The differential heats of adsorption of n-hexane increase slightly with loading, on the other hand the heat of adsorption of branched hexanes exhibits a decrease with loading. The diffusion rates on MFI of nhexane, 2-methylpentane and 2,3-dimethylbutane are in the same order of magnitude. However, the diffusion rate of 2,2-dimethylbutane is two orders of magnitude lower than rates of the other isomers. In the binary mixtures the components interact and the difference between the diffusion rates of the components decreases. The MFI zeolite presents equilibrium selectivity towards the less branched isomers. In conclusion, a separation process for linear/mono-branched alkanes + double-branched alkanes, has to be based on its equilibrium properties and not based on adsorption kinetics. Abbreviations Ddiffusivity, m 2 ·s −1 D c uptake diffusivity, m 2 ·s −1 D/r 2 diffusion time constant, s −1 K C adsorption equilibrium constant in the channels, kPa −1 K I adsorption equilibrium constant in the intersections, kPa −1 K H Henry's Law constant, mmol·g −1 ·kPa −1 p pressure (adsorbate concentration in the gas phase), Pa Q 0 initial heat of adsorption, kJ·mol −1 q loading (adsorbate concentration in the particles), mmol·g −1 q sat,C saturation loading in the channels, mmol·g −1 q sat,I saturation loading in the intersections, mmol·g −1 q t adsorbed amount at time t, mmol·g −1 q inf adsorbed amount at equilibrium, mmol·g −1 r particle radius, m V s the volume of the sample, cm 3 V g the volume of apparatus, cm 3 α K c V s /V g , (−)

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“…With the aim of getting further insight into the microscopic origin of this peculiar behavior, in this work, we have performed time-of-flight (TOF) neutron diffraction experiments of MEL with adsorbed argon at different loads, before and after the substep in the adsorption isotherm, at liquid nitrogen temperature. Diffraction experiments have often been used to investigate the structure of adsorbed fluids of varying complexity on zeolites (see, for example, refs , , , and − ). When only a few big molecules per unit cell are adsorbed, the structure of the adsorbate/adsorbent system can be determined by the Rietveld refinement method. − However, for the case of small gas molecules, such as argon, structural models have been most often constructed using MC simulations.…”

Section: Introductionmentioning

confidence: 99%

Evidence of a Structural Change in Pure-Silica MEL upon the Adsorption of Argon

Sánchez-Gil¹,

Noya²,

Guil³

et al. 2016

J. Phys. Chem. C

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In this work, we investigate the structure of argon adsorbed on pure-silica MEL at liquid nitrogen temperature. Our goal is to provide a microscopic interpretation for the appearance of a substep in the adsorption isotherm at intermediate loadings before saturation. For that purpose, we first perform time-of-flight neutron diffraction experiments of the loaded zeolite, before and after the substep. The measured spectra reveal that, after the substep, a considerable ordering of the adsorbate builds up, but there is also evidence of a zeolite structural change. These experimental data were then used in conjunction with Reverse Monte Carlo simulations to obtain theoretical structural models of the adsorbate/adsorbent system. Interestingly, the spatial distribution of the adsorbate predicted by Reverse Monte Carlo is considerably different from that obtained from grand canonical Monte Carlo simulations, even at half loading. We ascribe these discrepancies to deficiencies in the argon–zeolite interatomic potential. Besides, at high loading, we observe a different distribution of atoms along the channels parallel to the x-axis and those parallel to the y-axis. This might be attributed to a zeolite structural change distorting the tetragonal symmetry of MEL.

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Adsorption and Coadsorption of 2-methylpentane and 2,2-dimethylbutane in a ZSM-5 Zeolite

Cited by 10 publications

References 11 publications

Quasi-Equilibrated Thermodesorption Combined with Molecular Simulation for Adsorption and Separation of Hexane Isomers in Zeolites MFI and MEL

Quasi-Equilibrated Thermodesorption Combined with Molecular Simulation for Adsorption and Separation of Hexane Isomers in Zeolites MFI and MEL

Can alkane isomers be separated? Adsorption equilibrium and kinetic data for hexane isomers and their binary mixtures on MFI

Evidence of a Structural Change in Pure-Silica MEL upon the Adsorption of Argon

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