Multiple equilibria description of type H1 hysteresis in gas sorption isotherms of mesoporous materials

We report argon adsorption/desorption isotherms of MCM-41 and SBA-15. The shape all hysteresis loops we have observed corresponds to type H1. data been analyzed quantitatively using the multiple equilibria description applying notion metastable thermodynamic equilibrium. It is remarkable important that for both mesoporous materials desorption process can be understood according this but with a corresponding equilibrium constant. This procedure therefore allows determining values enthalpy free cavity thus obtain information not available so far. adsorption show first an increase characteristic Langmuir shape, followed by almost instantaneous filling cavities ends as soon are completely filled. SBA-15 at low relative pressure. pressure slightly below inflection point prel, infl = 0.312 marks beginning growth second layer, before takes place. interesting observe differ about 0.1 kJ/mol both, means driving force developing small. loop driven delicate changes occurring within cavities, partially or filled adsorbate. monolayer coverage processes decoupled from emptying processes. Knowing parameters ultimately helps better characterize understand experimental observations.