Calorimetric and Isosteric Heats of Adsorption of Substances with Molecules of Different Electronic Structure

Abstract

Calorimetric heats of adsorption have been measured for iso- and cyclo-pentane on NaX(86) zeolite at 140°C and for acetonitrile on carbon black and silica gel at 150°C. These heats have been compared with the corresponding isosteric values, calculated from isotherms measured over temperature ranges whose average values correspond to the above temperatures. The isosteric heats of adsorption coincide well with the calorimetric values in those cases where no change occurs in the mechanism for adsorbate–adsorbent interaction within the temperature range over which the isotherms have been measured. If this condition is not observed, the difference between the two sets of values can be quite considerable.