Analysis of gas adsorption in Kureha active carbon based on the slit-pore model and Monte-Carlo simulations

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Sweatman, M.B. and Quirke, N. and Zhu, W. and Kapteijn, R. (2006) Analysis of gas adsorption in Kureha active carbon based on the slit-pore model and Monte-Carlo simulations. Molecular Simulation, 32 (7). pp. 513-522. ISSN 1029-0435 (http://dx.doi.org/10.1080/08927020600717095)

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Abstract

We analyse the adsorption of carbon dioxide and several light alkenes and alkanes on Kureha active carbon at a range of temperatures. We find generally good agreement between the alkene and alkane isotherms at moderate to high pressure, but find that at the lowest relative pressures for each gas there are significant discrepancies that seem to be correlated with the strength of gas-surface interactions. This pattern is similar to that observed in our previous work on the adsorption of light alkenes and alkanes on active carbon, except the errors here are much smaller. One possible explanation for this error is poor diffusion in the experiments at the lowest relative pressures, leading to measurements of non-equilibrium states. We suggest that this poor diffusion might be caused by potential barriers (i.e. it is activated diffusion) in the narrowest pores. We also find that our analysis of the adsorption of carbon dioxide at 273 K is inconsistent with all the alkene and alkane data. We suggest this discrepancy arises because our model of gas-surface interactions does not take contributions from polar surface sites into account. Although this study is specific to Kureha active carbon, we expect that our conclusions are relevant to other studies of gas adsorption on active carbon; they highlight the need for great care when taking measurements at low pressures, and motivate improvements in molecular models for gas adsorption in active carbons.

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