Sorption of light paraffins in type-A zeolites. Analysis and interpretation of equilibrium isotherms

Ruthven, Douglas M.; Loughlin, Kevin F.

doi:10.1039/f19726800696

Cited by 91 publications

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“…It is interesting to notice that our calculated enthalpic data for methane, ethane and ethene are very close to the experimental isosteric heats reported by Ruthven et al [56] for adsorption in sodium-containing 5A zeolite, respectively, -21.8, -27.6 and -33.5 kJ·mol -1 [56,57], where a similar adsorption mechanism is anticipated for these small sorbates. This fact, together with the very good agreement between calculated enthalpies of interaction and experimental heats of adsorption reported in ref.…”

Section: Adsorption Of C 2 H X and C 3 H X Hydrocarbons In Ets-10supporting

confidence: 67%

A density functional theory study on the interaction of paraffins, olefins, and acetylenes with Na-ETS-10

2015

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High demand for economically viable separation processes like adsorptive separation for mixtures of hydrocarbons drives the need for understanding the interaction of hydrocarbons with titanosilicate adsorbents, to replace the energy intensive cryogenic hydrocarbon separation.Density functional theory (DFT) was used to optimize the geometries and calculate the enthalpies for the interactions between paraffins (C 2 H 6 , C 3 H 8 ), olefins (C 2 H 4 , C 3 H 6 ) and acetylenes (C 2 H 2 , C 3 H 4 ) with a cluster model of the Engelhard titanosilicatehaving sodium extra framework cations (Na-ETS-10). The DFT calculations were performed with theM06-L exchange correlation functional and were corrected for the basis set superposition error with the counterpoise method. The calculated enthalpies for the interaction of hydrocarbons with Na-ETS-10 decrease with the decrease in the number of carbon atoms, in the order acetylenes >olefins >paraffins,and compare well with experimental data available in the literature. The enthalpies calculated at the M06-L/6-31++G** level of theory for the two extreme cases, i.e., strongest and weakest interactions, are -62.8 kJ·mol -1 (C 3 H 4 ) and -26.9 kJ·mol -1 (C 2 H 6 ).Additionally, the calculated vibrational frequencies are in good agreement with the characteristic vibrational modes of ETS-10 and of the interactions of hydrocarbons with Na + in the 12-membered channel in ETS-10.

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Section: Adsorption Of C 2 H X and C 3 H X Hydrocarbons In Ets-10supporting

confidence: 67%

A density functional theory study on the interaction of paraffins, olefins, and acetylenes with Na-ETS-10

2015

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“…Zeolites The heats of adsorption and the Henry constants for the sorption of light paraffins in the 4A and 5A zeolites have been found t o be essentially the same (9) and one may expect that the values off,* will also be similar. Transition state theory (eq.…”

Section: Comparison Of D~flusiuities For 4 a And 5amentioning

confidence: 88%

“…4 of ref. 9). This theoretical isotherm has been shown t o provide a good fit of the experimental equilibrium data for light hydrocarbons in 5A zeolite (9, 10) over the region of low and intermediate sorbate concentrations and it has the correct asymptotic behavior since it reduces, in the low concentration limit, to Henry's Law.…”

Section: Concentration Dependence Of Dlfsusivi~ymentioning

confidence: 99%

Diffusion of Light Hydrocarbons in 5A Zeolite

Ruthven¹,

Derrah²,

Loughlin³

1973

Can. J. Chem.

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Experimental diffusivity data are presented for the diffusion of ethane, ethylene, propane, propylene, cyclopropane, n-butane, 1-butene, cis-2-butene, and trtms-2-butene in Linde 5A zeolite. It is shown that the concentration dependence of the diffusivity may be accounted for by considering the non-linearity of the eq~lilibri~~ni isotherms. Activation energies for diffusion, derived from the temperature dependence of the limiting diffusivity at zero sorbate concentration, show a clear correlation with the critical diameters of the sorbate molecules. The data are interpreted in terms of the transition state theory of diffusion and it is shown that, for the simpler molecules, this theory gives a quantitative!^ correct prediction of the pre-exponential factor governing the temperature dependence of the zeolitic diffusivity.Les donnees experimentales de diffi~sion a travers la zeolite Linde 5A ont CtC prbentkes pour ['ethane ethylene, propane, propylene, cyclopropane, n-butane, butene-1, cis butene-2 et trurrs butene-2. 11 a etC possible de tenir compte de la dipendance entre la diffusion et la concentration en considerant des equilibres isothermes non lineaires. Les energies d'activation de diffusion, derivees a partir d e la fonction diffusion limite-temperature pour une concentration nulle de sorbat, montrent une correlation claire avec les diametres critiques des molecules de sorbat. Les donnees ont ete interpretees par rapport a la theorie de I'etat de transition de diffusion et on a montre que pour des molecules simples, cette theorie conduit a une bonne prevision quantitative du facteur prkexponentiel gouvernant la diffusion ziolitique en fonction de la tenipkrature.[Traduit par le journal]Can. J. Chern.. 51, 3514 (1973) The kinetics of sorption of hydrocarbons in molecular sieve zeolites have been widely studied but there are, as yet, few systems for which the dependence of the zeolitic diffusivity on sorbate concentration, temperature and molecular geometry has been clearly established (1). T o obtain such information requires experimental data over a wide range of conditions since, with currently available experimental techniques, the inherent errors can easily conceal the real physical effects. In this laboratory we have used a gravimetric method t o measure the diffusivities of several light hydrocarbons in Linde 5A zeolite and the data from these studies (2-4) are analyzed and interpreted in this paper. The diffusivities for each sorbate show regular trends with concentration and temperature and the effect of molecular size is clearly evident. For the simpler molecules, diffusivities predicted theoretically from transition state theory show good agreement with the experimental data. Experimental

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“…In this expression v is the cavity volume, p is the molecular volume of the sorbate molecule, and m I v/P is the saturation limit, rounded to an integral number of molecules per cavity. This model has been found to provide a very satisfactory representation of the equilibrium isotherms for light hydrocarbons in type A zeolites (31) and also in Hchabazite (32). However the assumption of free molecular movement within a cavity is more likely to be correct for polyatomic molecules such as the hydrocarbons since the effect of molecular rotation will be to substantially reduce any energetic heterogeneity, thus favoring free mobility.…”

Section: Isotherm Modelsmentioning

confidence: 99%

“…An alternative model isotherm has recently been developed for a system in which the sorbed molecules are confined within a particular cavity but are freely mobile within the cavity (30,31). For such a system, simplified considerations of the reduction in free volume available to the sorbed molecules lead to the following expression for the isotherm Can.…”

Section: Isotherm Modelsmentioning

confidence: 99%

Sorption of the Inert Gases (Ar, Kr, and Xe) in Type A Zeolites

Derrah¹,

Ruthven²

1975

Can. J. Chem.

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RUSSELL IAN DERRAH and DOUGLAS MORRIS RUTHVEN. Can. J. Chem. 53,996 (1975). Theoretical potential profiles for Ar, Kr, and Xe occluded in an idealized 5A zeolite are calculated and used to evaluate the Henry's law equilibrium constants for these species. Calculations were made using the three common formulae to estimate the dispersion constants (Kirkwood-Mueller, Slater-Kirkwood, and London) and the theoretical Henry constants are compared with the values-obtained directly from experimental equilibrium isotherms. For both Kr and Xe the Slater-Kirkwood formula gives the best agreement with the experimental values while, for argon, the London formula is best. At higher concentrations the isotherms for Kr can be well represented by a simple Langrnuir expression with eleven sites per cavity while for Xe there appears to be a transition from localized sorption at low temperatures to a mobile adsorbed phase at higher temperatures. These conclusions are qualitatively consistent with the results of the theoretical potential calculations.RUSSELL IAN DERRAH et DOUGLAS MORRIS RUTWEN. Can. J. Chem. 53,996 (1975). On calcule les profils potentiels theoriques de Ar, Kr et Xe occlus dans une zeolithe 5A idealis&; on utilise les valeurs ainsi calcul&s pour kvaluer les constantes dY6quilibre de la loi d'Henry pour ces especes. On a fait des calculs utilisant les trois formules ordinaires pour estimer les contantes de dispersion (Kirkwood-Mueller, Slater-Kirkwood et London) et l'on compare les constantes theoriques #Henry avec les valeurs obtenues directement a partir des isothermes experimentales d'equilibre. Pour le Kr et le Xe, la formule de Slater-Kirkwood donne la meilleure relation avec les valeurs experimentales alors que pour I'argon, la formule de London est la meilleure. A des concentrations plus hautes, les isothermes de Kr peuvent aussi dtre presentes par une expression simple de Langmuir avec onze sites par cavite alors que pour Xe il semble qu'il existe une transition passant d'une sorption localisee a basse temperature a une phase adsorb& mobile a plus haute tempbature. Ces conclusions sont qualitativement en accord avec les rksultats des calculs potentiels thioriques.[Traduit par le journal]

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Sorption of light paraffins in type-A zeolites. Analysis and interpretation of equilibrium isotherms

Cited by 91 publications

References 0 publications

A density functional theory study on the interaction of paraffins, olefins, and acetylenes with Na-ETS-10

A density functional theory study on the interaction of paraffins, olefins, and acetylenes with Na-ETS-10

Diffusion of Light Hydrocarbons in 5A Zeolite

Sorption of the Inert Gases (Ar, Kr, and Xe) in Type A Zeolites

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