Physical adsorption of gases at high pressure

This is the authors' abstract. We don't add key points for this paper.

A grand canonical ensemble Monte Carlo study is made of the adsorption of a gas of simple molecules in the space between two infinite, flat, parallel surfaces (slit-like pores) as a function of their separation, h, at various temperatures. Above the critical temperature the overall shape of the adsorption isotherm is independent of h but both the maximum adsorption and the pressure, at which the maximum occurs, decrease as h decreases. Below the critical temperature the adsorption isotherm follows that obtained for an isolated surface up to a pressure p 1 beyond which the adsorption excess increases sharply with pressure to a plateau value. This rapid increase is interpreted in terms of condensation of the gas in the cavity between the surfaces, i.e. capillary condensation. As h is decreased the value of p 1 decreases. When h is comparable with the diameter of the adsorbate molecules the cavity is full at all readily attainable pressures. The results are further interpreted in terms of the singlet distribution function of the adsorbate and its behaviour as a function of pressure.