Probing pore structure of microporous and mesoporous molecular sieves by quasi-equilibrated temperature programmed desorption and adsorption of n-nonane

Measurements of temperature programmed desorption and adsorption of n-nonane in quasi-equilibrated conditions using TPD apparatus equipped with a TCD detector were performed for some microporous (zeolites HZSM-5 and HY) and mesoporous materials (MCM-41 and SBA-15). Complex adsorption/desorption profiles with high temperature desorption peaks related to adsorption in the micropores and low temperature peaks attributed to capillary condensation in the mesopores were observed. Diameters of the mesopores calculated from the thermodesorption data (basing on the Kelvin equation for capillary condensation and the Henry function for the adsorbed film thickness) are in agreement with those determined from N2 adsorption isotherms. Values of the adsorption heat of n-nonane were determined by fitting the Henry function to the high temperature range of the integrated thermodesorption profiles.