Textural Characterization and Energetics of Porous Solids by Adsorption Calorimetry

An adsorption microcalorimeter was designed and built in our laboratory and used for the determination of differential adsorption heats in different samples of porous solids: activated carbon granules, activated carbon pellets, an activated carbon monolith and a zeolite sample. This work shows the relationship between adsorption heat and the pore size of different porous solids using adsorption of NH3, CO and N2O. The result shows that the thermal effect can be related with textural properties and superficial chemical groups of the studied porous solids. The values of differential heats of N2O adsorption in the investigated systems have shown that this interaction is weaker than that with CO. Small amounts of N2O are chemisorbed in the investigated systems. For the room temperature adsorption of N2O, the strongest active sites for the interaction with Brönsted acid groups in the ACM structure were identified. The values determined are between −60 kJ/mol and −110 kJ/mol for ZMOR and ACM, respectively, for the adsorption of N2O and −95 kJ/mol and −130 kJ/mol for the adsorption of CO.