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A procedure to find thermodynamic equilibrium constants for CO2 and CH4 adsorption on activated carbon

Abstract

Thermodynamic equilibrium for adsorption means that the chemical potential of gas and adsorbed phase are equal. A precise knowledge of the chemical potential is, however, often lacking, because the activity coefficient of the adsorbate is not known. Adsorption isotherms are therefore commonly fitted to ideal models such as the Langmuir, Sips or Henry models. We propose here a new procedure to find the activity coefficient and the equilibrium constant for adsorption which uses the thermodynamic factor. Instead of fitting the data to a model, we calculate the thermodynamic factor and use this to find first the activity coefficient. We show, using published molecular simulation data, how this procedure gives the thermodynamic equilibrium constant and enthalpies of adsorption for CO2(g) on graphite. We also use published experimental data to find similar thermodynamic properties of CO2(g) and of CH4(g) adsorbed on activated carbon. The procedure gives a higher accuracy in the determination of enthalpies of adsorption than ideal models do.

Category

Academic article

Client

  • Notur/NorStore / NN9229K
  • Notur/NorStore / NN4504K
  • Notur/NorStore / nn4504k
  • Notur/NorStore / nn9229k
  • Research Council of Norway (RCN) / 209337

Language

English

Author(s)

  • Thuat Trinh
  • Titus Sebastiaan van Erp
  • Dick Bedeaux
  • Signe Kjelstrup
  • Carlos Adolfo Grande

Affiliation

  • Norwegian University of Science and Technology
  • Delft University of Technology
  • SINTEF Industry / Process Technology

Year

2015

Published in

Physical Chemistry, Chemical Physics - PCCP

ISSN

1463-9076

Publisher

Royal Society of Chemistry (RSC) Publishing

Volume

17

Issue

12

Page(s)

8223 - 8230

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