Diffusion of gases in porous solids over a thousand-fold pressure range

Henry, J.P.; Cunningham, R. S.; Geankoplis, C. J.

doi:10.1016/0009-2509(67)80099-x

Cited by 36 publications

(21 citation statements)

References 16 publications

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“…All of the models from which the dusty gas equation is derived also predict that the ratio of the fluxes of two counterdiffusing gases should be equal to the negative reciprocal of the square root of the two gases' molecular weights, that is, The theory predicts that this relationship should be true irrespective of temperature or total pressure, assuming the system is both isothermal and isobaric. The ratio of the fluxes of two gases counterdiffusing under these conditions within a porous medium has been experimentally measured, and most investigators reported that the theoretical flux ratio was observed within experimental error (Wicke and Hugo, 1961;Evans et a]., 1961;Henry et al, 1967;Cunninghani and Geankoplis, 1968;Horak and Schneider. 1971).…”

Section: Previous Workmentioning

confidence: 99%

“…The dusty gas equation has also been checked by some investigators for its ability to predict changes of flux with total pressure. Scott and Dullien (1962) and Henry et al (1967) studied some unimodal materials, and Rothfeld ( 1963), Henry et al ( 1967), and Cunningham and Geankoplis ( 1968) studied some bimodal materials. Satisfactory agreement within experimental error was reported in all cases between the predictions of the equation and the experimental data.…”

Section: Previous Workmentioning

confidence: 99%

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Using the dusty gas diffusion equation in catalyst pores smaller than 50 Å radius

Omata

Brown

1972

AIChE Journal

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When the dusty gas diffusion equation is applied to materials containing pores with radii below 50 Å, the observed diffusion behavior in these smaller pore systems can be quite different from that predicted by the equation. Higher temperatures and in some cases higher pressures tend to lessen the deviations between prediction and experiment. The observed deviations are probably caused by surface transport and by momentum transfer between gas molecules and pore walls during molecular flight. For bimodal materials, an additional factor can be the inapplicability of the equation to systems of parallel micro‐ and macropores. Excellent agreement between theory and experiment occurs for large‐pore unimodal systems.

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Section: Previous Workmentioning

confidence: 99%

Section: Previous Workmentioning

confidence: 99%

Using the dusty gas diffusion equation in catalyst pores smaller than 50 Å radius

Omata

Brown

1972

AIChE Journal

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“…However, we offer below some evidence which we believe verifies qualitatively a number of the results presented here. Those diffusion data which exist for nonadsorbing or very weakly adsorbing gases in microporous media would tend to suggest that the tortuosity of the pores in a given class of materials increases with decrease in mean pore radius (Henry et al, 1967;Gangwal et al, 1979). This trend may well be due to differences in the pore structure, however another possibility is the increasing influence of steric hindrance in smaller pores.…”

Section: Dlscusslonmentioning

confidence: 99%

“…The dusty gas model, which was originally proposed by Derjaguin and Bakanov (1957) and extended and studied in greater detail by Mason and others (1961Mason and others ( ,1963Mason and others ( ,1964Mason and others ( ,1967, is now accepted as providing a suitable description for gas diffusion and flow in porous media over a wide range of conditions. With a proper choice of porous medium structure factors, and/or by introducing the concept of the pore size distribution, reasonably accurate predictive transport models may be obtained (Wakao and Smith, 1962; Johnson and Stewart, 1965; Henry et al, 1967; Brown et al, 1969; Feng et al, 1973Feng et al, , 1974. In certain cases, however, the dusty gas model cannot describe the transport process adequately.…”

Section: Scopementioning

confidence: 99%

Hindered diffusion of gases in “Leaky” membranes using the dusty gas model

MacElroy

Kelly

1985

AIChE Journal

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The modified Enskog theory of van Beijeren and Ernst for dense fluid mixtures of rigid spheres is applied to diffusion of inert, nonadsorbing gases in microporous "leaky" membranes. Utilizing the concept of a dense dusty gas, the resulting expressions for the permeability and flux ratio illustrate the influence of steric hindrance on the transport process. The results obtained serve as corrections to the original dusty gas model of Mason and others. SCOPEThe dusty gas model, which was originally proposed by Derjaguin and Bakanov (1957) and extended and studied in greater detail by Mason and others (1961Mason and others ( ,1963Mason and others ( ,1964Mason and others ( ,1967, is now accepted as providing a suitable description for gas diffusion and flow in porous media over a wide range of conditions. With a proper choice of porous medium structure factors, and/or by introducing the concept of the pore size distribution, reasonably accurate predictive transport models may be obtained (Wakao and Smith, 1962 Feng et al., 1973Feng et al., , 1974. In certain cases, however, the dusty gas model cannot describe the transport process adequately. This has been found to be the case when the gas species adsorb, forming a mobile adsorbed phase Brown, 1973,1974; Spencer and Brown, 1975;Thakur et al., 1980); it is also inadequate for diffusion in pores of 50 A radius or less (Omata and Brown, 1972) and cannot be expected to describe diffusion in the configurational regime (Weisz, 1973). The main reason for the failure of the dusty gas model in these cases lies in its use of dilute gas kinetic theory, inferring that the number density of the "dust" species is low that each of the components in the dilute gas mixture may be represented as point particles and that the existence of bound states (molecular clustering) may be neglected. When it is recognized that the structure of rigid isotropic porous media more closely resembles a "frozen" dense fluid, it is more appropriate to use dense fluid kinetic theory as a basis for a dusty gas model.In this work the influence of membrane density and the molecular size of diffusing, nonadsorbing gases is investigated by applying the dusty gas concept to the rigid sphere model of dense fluid mixtures. Expressions are obtained for the permeability and the flux ratio of counterdiffusing gases which introduce a new parameter, the dimensionless ratio of mollecular radius to membrane particle radius, into the results of the original dusty gas model.

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“…Using this new pressure range and capil laries, the 33 Rothfeld capillary Eq. (3) can also be tested.…”

Section: A Diffusion Of Gases At High Pressuresmentioning

confidence: 99%

KNUDSEN AND MOLECULAR DIFFUSION OF GASES IN CAPILLARIES AND POROUS SOLIDS OVER LARGE PRESSURE RANGES. Final Report, April 1, 1967--December 31, 1971.

Geankoplis¹

1972

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Diffusion of gases in porous solids over a thousand-fold pressure range

Cited by 36 publications

References 16 publications

Using the dusty gas diffusion equation in catalyst pores smaller than 50 Å radius

Using the dusty gas diffusion equation in catalyst pores smaller than 50 Å radius

Hindered diffusion of gases in “Leaky” membranes using the dusty gas model

KNUDSEN AND MOLECULAR DIFFUSION OF GASES IN CAPILLARIES AND POROUS SOLIDS OVER LARGE PRESSURE RANGES. Final Report, April 1, 1967--December 31, 1971.

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