A study of the mechanism of micropore filling: II. Pore filling of a microporous silica

Abstract The adsorption isotherms of argon, benzene, water and two alcohols by a microporous silica are found to be best described by a two-term Dubinin—Radushkevich equation. A comparison of the data fit between benzene, as standard, and the alcohols and between argon, as standard, and the alcohols illustrates the inability of the Theory for Volume Filling of Micropores to predict isotherms involving nondispersion interactions. Differentiation of the two-term DR equation gives the probability distribution of the micropore and supermicropore filling contribution to the cumulative distribution of micropore filling. From the curves for each adsorbate, at sufficiently low pressures, it is proposed that the micropores fill almost exclusively at the expense of the supermicropores. The mechanism of supermicropore filling is proposed to be a transition between volume filling in micropores proper and capillary condensation.