Condensation enthalpies of <Emphasis Type="Italic">n</Emphasis>-hexane in micelle-templated mesoporous silicas

The isosteric enthalpies of adsorption of n-hexane on ordered mesoporous silica of pore diameter between 3 and 10 nm have been measured. The heat of capillary condensation increases when mesopores are smaller. Capillary condensation of n-hexane in 3 nm mesopores is 20% more exothermic than the condensation on a flat liquid surface. The results are in good agreement with a model which takes into account the energetic contribution of the interface between the adsorbed layer and the vapour phase.