Intraparticle diffusion coefficients in packed columns: Measurement by arrested‐flow gas chromatography

Park, In-Soo; Smith, J. M.; McCoy, Benjamin J.

doi:10.1002/aic.690330706

Cited by 20 publications

(13 citation statements)

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“…To test consistency with earlier results, one experiment was done with adsorbing C02 in a column packed with large-pore particles of Alcoa alumina. The result for intraparticle diffusivity was identical to that reported by Park et al (1987), when Eq. 2 is used for the capacity of the column for the adsorbing gas.…”

supporting

confidence: 88%

“…As mentioned, adsorption was negligible in columns packed with particles of Varian firebrick and Alcoa alumina, Table 2. The intraparticle diffusivity, calculated by the method of Park et al (1987) for a nonadsorbing gas, gave essentially the same values as reported by Park.…”

supporting

confidence: 80%

“…Negligible adsorption was observed for all the large-pore particles, except for C 0 2 on Alcoa alumina. The heat of adsorption for methane on T-126 particles was determined to be A H = -10.4 kJ/mol from a linear regression of In K versus 1 f T. Figure 2 shows experimentally-measured values of variance, plotted versus stopped-time, for nonporous glass beads (Park et al, 1987) and for the three large-pore particles (the three upper, and the lower lines). The adsorbing gas was methane except where noted.…”

mentioning

confidence: 99%

“…variance for the methane-T-126 system at temperatures from 3 13 to 373 K. Only these results were used for calculating internal tortuosity factors for porous particles, defined as Here, Dj is the effective intraparticle diffusivity calculated from D, (obtained from Eq. l), with either the Maxwell, Burger, Rayieigh, or Jeffrey models for diffusion in a composite medium (Park et al, 1987). These calculations require a value for the external tortuosity factor applicable for the void region in the bed.…”

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confidence: 99%

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Diffusion and adsorption in arrested‐flow chromatography

Smith

McCoy

1989

AIChE Journal

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confidence: 88%

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confidence: 80%

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confidence: 99%

mentioning

confidence: 99%

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Diffusion and adsorption in arrested‐flow chromatography

Smith

McCoy

1989

AIChE Journal

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“…The objectives of the study by Johnson et al [ Z I ] were to investigate sorption of p-xylene on montrnorillonite and to study the influence of water content on the chemisorption reaction on montmorillonite. Chiou and Shoup [22] investigated the sorption of some VOCs on soil and the effects of humidity on the sorptive mechanisms. Their study showed that water vapor sharply reduced the sorption capacity of organic compounds on dry soil.…”

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Nonconvective movement of VOCs in moist soil

Cabbar

McCoy

1996

Environ. Prog.

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Diffusion in packed beds of porous particles

Whitaker¹

1988

AIChE Journal

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The determination of the effective diffusivity for small porous particles (the intraparticle diffusion coefficient) by direct experimental methods is generally not possible. Because of this, one is forced to measure the overall effective diffusivity for packed beds of porous particles and subsequently extract the particle effective diffusivity by means of a theoretical analysis of the two-region diffusion process. In a recent study by Park et al. (1987), experiments using arrested-flow chromatography were described and a method of obtaining the particle effective diffusivity was presented. Based on solutions of the overall diffusion equation and experimental measurements, values of D, were determined for a variety of packed beds of porous particles. In order to calculate values of the particle effective diffusivity, semiempirical equations were developed on the basis of the classic works of Maxwell (1873), Rayleigh (1892), Burger (1919), andJeffrey (1973). All of these represent high void fraction theories for steady heat conduction in two-phase systems.Rather than modify special theories in order to extract particle effective diffusivities from measured values of D,, it would seem wise to make use of the general solution to the problem (Whitaker, 1983). The system under consideration is shown in Figure 1, where the @ phase represents the homogeneous gas phase and the u phase represents the porous particle phase. The diffusion equation for the gas phase contained within the porous particles must be volume-averaged and this is done in terms of the averaging volume ' v, indicated in Figure 1. An expanded view of the u phase averaging volume is shown in Figure 2 where the K phase represents the rigid solid and the y phase is used to identify the gas within the porous particles. A detailed analysis of diffusion in porous catalysts (Whitaker, 1987) leads to a governing equation for the u phase, and for dilute solutions or equi- (Gray, 1975) of the diffusing species in the u phase, and ce represents the point concentration of the diffusing species in the @ phase. One must keep in mind that a), represents an effective diffusivity for the porous particles.It is also important to keep in mind that a)# represents the molecular diffusivity of the diffusing species in the @ phase, and that the patching together of volume-averaged transport equations and point transport equations is not necessarily an obvious process. The details are given in the original paper. The structure of the boundary value problem given by Eqs. 2-5 is almost identical to a transient heat conduction problem, and it would be identical if it were not for the presence of the particle void fraction, cy, in the boundary condition given by Eq. 4. Clearly the steady state diffusion problem is analogous to the heat conduction problem, and this has important consequences for the solution of the closure problem (Crapiste et al., 1986).Since the position of the interface between the porous particles and the surrounding gas phase is unknown, one seeks a voiume-av...

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Intraparticle diffusion coefficients in packed columns: Measurement by arrested‐flow gas chromatography

Cited by 20 publications

References 17 publications

Diffusion and adsorption in arrested‐flow chromatography

Diffusion and adsorption in arrested‐flow chromatography

Nonconvective movement of VOCs in moist soil

Diffusion in packed beds of porous particles

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