n-Heptane adsorption and desorption on porous silica observed by positron annihilation lifetime spectroscopy

Many papers are devoted to interpretation of adsorption of gases on solids. A complete understanding of the mechanism of pore filling and emptying by adsorbate molecules is a fundamental meaning for obtaining the accurate parameters characterizing the pore structure. The present article deals with application of positron annihilation lifetime spectroscopy (PALS) for determination of free volumes dimensions in pores upon adsorption process. On the basis of PALS spectra a comprehensive insight into adsorption mechanism of n-heptane in silica gel is presented.

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► The determination of porous structure by positron annihilation lifetime spectroscopy.
► A new insight into mechanism of n-heptane adsorption on silica gel.
► In situ measurements of free volume size during adsorption/desorption from mesopores.
► Phase transition of adsorbate inside pores at different pressure.