Microporous Adsorbents for a Selective Separation of Carbon Dioxide from Mixtures with Methane and Nitrogen

J. Pavlíček and S. J. Scaife

Abstract
The study describes a theoretical approach of the design of a micro-structure of adsorbents for a selective separation of carbon dioxide from gaseous mixtures at ambient conditions. Adsorption isotherms of carbon dioxide, nitrogen and methane, were experimentally measured on two model carbonaceous surfaces at 293.1 K. Non-local density functional theory was used to predict theoretically the behaviour of these gases as adsorbates in slit-shaped pores for a pore size range of 0.5–5 nm. The gas-solid potential parameters were obtained by fitting the calculated adsorption isotherm of a single model adsorbent surface (H* = 100) to the experimental data. Prediction of behaviour of gas mixtures in adsorption and selectivity calculations were obtained from ideal adsorbed solution theory. It was shown that a set of separation factors evaluated for a particular pore size range give a potential to design completely a microporous structure of a desired carbonaceous adsorbent. To such a surface, macroscopically represented by average selectivity factors, a real adsorbent characterised experimentally by the pore size distribution, could be assigned.

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Keywords
Density Functional Theory, Ideal Adsorbed Solution theory, separation of gases, adsorption of nitrogen, methane and carbon dioxide