New low-cost and compact experimental system for characterization of porous materials by quasi-equilibrated thermodesorption of nonane or water

The new low-cost, simple and compact experimental system for characterization of porous materials by quasi-equilibrated temperature-programmed desorption and adsorption (QE-TPDA) based on the miniature microprocessor-controlled thermal conductivity sensor Sensirion STC31 has been described in detail. The performance of the new system has been tested in QE-TPDA measurements of nonane for high-silica zeolites Y and ZSM-5, as well as for a series of ordered mesoporous silicas SBA-15. Although very good qualitative agreement of the QE-TPDA profiles measured in the new system with those observed in a standard one was found, slightly lower saturation sorption capacities based on the new profiles were obtained. The pores size distributions (PSDs) calculated from the new nonane QE-TPDA profiles for SBA-15 silicas showed very good agreement with those obtained from N₂ adsorption isotherms using the NLDFT method. An excellent correlation between the pore size values based on both sets of PSDs was found. The new system was also applied in the QE-TPDA of water for selected metal-organic frameworks (MOFs). The QE-TPDA profiles of water observed for two fumarate containing MOFs Al-fum (aka Basolite A520) and MIL-88 A were consistent with the adsorption-desorption isotherms obtained in a standard manometric apparatus. Hydrothermal stability tests of these MOFs, based on prolonged water QE-TPDA measurements, revealed the onset of structure degradation of Al-fum at 350 °C and at 250 °C for MIL-88 A.