Calorimetric study of capillary condensation and application to the texture determination of a mesoporous solid

The author proposes a new porosimetric method using calorimetric measurements. Therefore, a study of the capillary condensate was needed to compare its thermodynamic behaviour with that of the bulk liquid. The study of the heats of capillary condensation is divided in two parts. The first one, theoretical, is a calculation of those heats and entropies of an adsorbed or condensed phase. The second one is grounded on experimental measurements and uses a microcalorimeter associated with an automatic volumetric apparatus especially designed. This study shows that the heat of capillary condensation exceeds the heat of condensation in bulk liquid essentially by a quantity proportional to the area change in the pores. This results allows to obtain, from integral heats measurements, the surface and pore volume of mesoporous solids. The proposed method is also based on the diagram of the isotherm curves of integral heats, showing an hysteresis loop and giving more information about the shape of capillaries and pores distributions. The comparison of various textural data obtained from well known methods with those based on calorimetric measurements settles the validity of such a study