Gas adsorption isotherms from composition and flow-rate transient times in chromatographic columns I. Basic theory and a binary experimental test

Mason, Geoffrey; Buffham, B.A.

doi:10.1098/rspa.1996.0065

Cited by 10 publications

(1 citation statement)

References 19 publications

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“…Ideally, one would wish to make an additional measurement at each gas composition and derive an additional relation to complement eq 9. We, , and others, have advocated using outlet flow-rate measurements. When this is done, the binary isotherm gradients at a single composition may be determined 2,8 from outlet composition and flow-rate measurements.…”

Section: The Chromatographic Methodsmentioning

confidence: 99%

Binary Adsorption Isotherms from Chromatographic Retention Times

Buffham

Mason

Heslop

1999

Ind. Eng. Chem. Res.

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A new method to determine binary adsorption isotherms from a set of binary chromatographic retention-time experiments is proposed. It differs from existing methods in two main ways. The first is that a functional form is assumed for the isotherms. The second is that it does not require supplementary measurements to be made. The isotherm parameters are found by a computer search. Any other available data may be incorporated into the method. The method is tested on retention-time data for the coadsorption of nitrogen and argon on 5A molecular sieves and of ethane and ethylene on 13X molecular sieves. Very precise experimental data are required if the isotherms are to be reconstructed solely from retention data.

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Section: The Chromatographic Methodsmentioning

confidence: 99%

Binary Adsorption Isotherms from Chromatographic Retention Times

Buffham

Mason

Heslop

1999

Ind. Eng. Chem. Res.

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On the Chromatographic Measurement of Equilibrium Isotherms Using Large Concentration Steps

Brandani

2005

Adsorption

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The measurement of equilibrium isotherms from the dynamic response of an adsorption column subject to a large pulse or step change in inlet concentration requires the simultaneous measurement of concentration and flowrate. Based on the observation that for a single sorbate-carrier system the concentration and velocity transients are coupled, a procedure to estimate the true column outlet carrier flowrate from the measured concentration signal is derived, which is consistent with an overall mass balance of the carrier gas. The proposed approach has been validated using experimental breakthrough curves for CO 2 on UOP HiSIV 3000 pellets for integral step changes up to 75% in CO 2 concentration.

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Binary chromatographic retention times from perturbations in flowrate and composition

Heslop¹,

Buffham

Mason

2007

Adsorption

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This work is a theoretical and experimental investigation of the binary retention time (t step) when the disturbance is made to a chromatographic system by adding a small flow of one of the pure components. The established theory is for addition of a pulse: in this case, the retention time (t pulse) depends on the two binary isotherm gradients, and should be independent of the choice of pulse gas. From the column material balance, the value of t step also depends on the column pressure drop and perturbation gas-the value of t step should always be greater for the more-adsorbed component. The theory has been validated from results on the nitrogen-argon-5A zeolite system at 25, 54 and 81 °C. For a 50% mixture at 25 °C with a column pressure drop of 0.1 bar, the values of t step are 257 and 254 seconds for the nitrogen and argon perturbations. The values of t step are different because addition of the perturbation flow causes a very small increase in average column pressure (about 0.5 mbar), which causes the binary isotherm gradients to be measured in (slightly) different directions along the isotherm surface. The intention is to determine the value of t step for the case of a zero change in the average column pressure: experimentally, this would require a column with a zero pressure drop. The material balance shows that t step for a column with a zero pressure drop is obtained from a simple weighted function of the values of t step for the two pure-component perturbations. Accurate determination is essential because the 'zero pressure drop' values are used to determine binary adsorption isotherms which are, of course, at a fixed pressure

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Gas adsorption isotherms from composition and flow-rate transient times in chromatographic columns I. Basic theory and a binary experimental test

Cited by 10 publications

References 19 publications

Binary Adsorption Isotherms from Chromatographic Retention Times

Binary Adsorption Isotherms from Chromatographic Retention Times

On the Chromatographic Measurement of Equilibrium Isotherms Using Large Concentration Steps

Binary chromatographic retention times from perturbations in flowrate and composition

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