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Determination of Pore Size Distribution from Density Functional Theory: A Comparison of Nitrogen and Argon Results

1994; Elsevier BV; Linguagem: Inglês

10.1016/s0167-2991(08)63067-0

2542-6613

James P. Olivier, W.B. Conklin, M. v. Szombathely,

Advanced Chemical Physics Studies

Model isotherms have been calculated for the adsorption of nitrogen and argon at the temperature of their normal boiling points, both for a free surface and for the surface within slit-shaped pores using density functional theory. The calculations incorporate a smoothed density approximation (SDA) for the hard-sphere repulsion terms, and Monte Carlo simulation was used to confirm important aspects of the adsorbate density distribution. Free surface isotherms were tested against experimental isotherms for a non-porous graphite, Sterling FT-G (2700), and surface energy analysis was performed to determine the characteristic gas-solid interaction values. Density functional theory was found to yield a very good description of the adsorption isotherm in the monolayer region; however, the theory in its present form underestimates the pressure at which second and higher layer formation becomes important.