Dependence of diffusive permeation rates on upstream and downstream pressures

Greenlaw, F.W.; Shelden, Ronald A.; Thompson, Edward V.

doi:10.1016/s0376-7388(00)83261-5

Cited by 113 publications

(28 citation statements)

References 6 publications

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“…For downstream pressure greater than 1706 Pa, both the decrease in flux and the increase of separation factor will be observed prominently. In the present case, an increase in downstream pressure increases the concentration of the more volatile component, in the present case, ethanol in the permeate as reported in the penraporation of hexane-heptane mixture through polyethylene film by Greenlaw et al 33 The remainder of this paper, then, is devoted to the description of our work with the downstream pressure of both 400 Pa (3.0 torr) and 3330 Pa (25.0 tom). Figure 4 shows results of the pervaporation experiments for membranes Tl-T4, where the weight fraction of ethanol in permeate are plotted as a function of ethanol fraction in feed.…”

Section: Characterization Of Membranessupporting

confidence: 59%

Application and development of synthetic polymer membranes. II. Separation of aqueous ethanol solution through poly(tert‐butyl methacrylate‐co‐styrene) membranes

Yoshikawa

Ohsawa

Tanigaki

et al. 1989

J of Applied Polymer Sci

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SynopsisSeparation of aqueous ethanol solution was carried out by pervaporation using a membrane which consisted of common polymer membranes. A membrane obtained from poly( tert-butyl methacrylate-co-styrene) was effective for a selective separation of ethanol from aqueous ethanol solution by pervaporation technique. The pervaporation of ethanol-water mixture through the present membranes was analyzed as a solution-diffusion process, on the assumption that the both diffusion coefficients of each component are an exponential function of ethanol concentration.

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Section: Characterization Of Membranessupporting

confidence: 59%

Application and development of synthetic polymer membranes. II. Separation of aqueous ethanol solution through poly(tert‐butyl methacrylate‐co‐styrene) membranes

Yoshikawa

Ohsawa

Tanigaki

et al. 1989

J of Applied Polymer Sci

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“…Greenlaw et al 5 and Lee 12 discussed the pervaporation transport using the solutiondiffusion model with an assumption that the pressure of the permeant inside the membrane is constant and equal to the upstream pressure across the membrane. In particular, Greenlaw et al have shown explicitly the effect of the upstream and the downstream pressure on the pervaporation flux and calculated the flux numerically under different conditions using the parameters listed in Table I.…”

Section: Combination Of Liquid Phase and Vapor Phase Transportmentioning

confidence: 99%

Effect of Upstream Pressure on the Flux of Single Permeant in Pervaporation

Bai

Fouda

Matsuura

1994

Polym J

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ABSTRACT:The effect of the upstream pressure on the pervaporation flux of water was studied both theoretically and experimentally. The increase in the pervaporation flux with an increase in the upstream pressure was predicted using newly developed transport equations that allow the pressure change across the membrane and include both liquid and vapor phase transport. The conventional solution-diffusion model, on the other hand, fails to predict the effect of the upstream pressure, particularly when an assumption is made that the pressure of the permeant inside the membrane is constant across the membrane and is equal to the upstream pressure. The pervaporation flux of water through a polydimethysiloxane membrane and an aromatic polyamide membrane was found, experimentally, to increase with an increase in the upstream pressure.KEY WORDS Pervaporation / Membrane / Aromatic Polyamide / Polydimethylsiloxane / Membrane Transport / Pervaporation has been recognized recently as one of the most versatile membrane separation processes. Fundamental research on pervaporation has been carried out intensively parallel to the growth of the number of industrial applications. At present the majority of studies on pervaporation transport is based on the solution-diffusion model 1 -5 with few exceptions that are based on the pore model. 6 -8 Although the transport equations derived from both models explain the effect of the downstream pressure on pervaporation flux equally well, they come to different conclusions regarding the effect of the upstream pressure;i.e., the solution-diffusion model predicts little effect of the upstream pressure, when the downstream pressure is nearly equal to zero, while the pore model predicts that the pervaporation flux should change linearly with an increase in the upstream pressure. There are t To whom correspondence should be addressed. llOO also two different kinds of experimental data. Whereas Greenlaw et al. and Paul and Ebralima concluded that the pervaporation flux remained constant with an increase of the upstream pressure for the system hexane/ polyethylene and cyclohexane/highly swollen cross-linked rubbery membrane, 5 • 9 respectively, Okada and Matsuura showed that the flux increased linearly for the system ethyl alcohol/heptane mixture in cellulose membranes of different pore sizes. 6 It has to be noted that the solution-diffusion mechanism does not necessarily predict no upstream pressure effect. The above prediction can only be made under an assumption that the pressure of the permeant remains the same as the upstream pressure across the membrane. When the above assumption is removed, the change of the pervaporation flux is predicted with a change in the upstream pressure. It is

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“…The productivity and separation selectivity between different permeants are not only dependent on the solubility and diffusivity of each permeant but also on their solubility and diffusivity ratios through the membrane. Excellent agreements between experimental data and theoretical predictions by means of the solution-diffusion model have been reported for both defect-free dense flat membranes and asymmetric membranes consisting of a thin defect-free dense-selective layer [10][11][12][13][14][15][16][17][18][19][20][21][22].…”

Section: Introductionmentioning

confidence: 98%