(569c) O2 and N2 Kinetics on CMS up to 5 Bar Using a Novel High Pressure Adsorption Differential Volumetric Apparatus (ADVA)

Carbon Molecular Sieves (CMS) are largely employed in Pressure Swing Adsorption (PSA) systems designed for the kinetic separation of N₂ and O₂ from air. The kinetic properties of these adsorbents have attracted the interest of several researchers in the past decades, but the gas transport mechanism in these systems is complex and still not fully understood. In a previous publication [1], we reported low pressure kinetic experiments on Takeda 3K-172 CMS pellets using a commercial volumetric apparatus. The analysis proved that the CO₂ mass transport mechanism is well interpreted by a linear driving force model with a distribution of time constants.

Here we extend the study by investigating adsorption kinetics at pressures up to 5 bar using a newly designed Adsorption Differential Volumetric Apparatus (ADVA) for high pressure kinetic measurements. The system’s design is similar to the low pressure ADVA [2], with two symmetrical branches (namely, sample and reference side) connected by a differential pressure transducer to monitor the pressure as the gas expands from the dosing and the uptake volumes. The system is specifically designed for kinetic measurements up to 60 bar, with very small volumes, high acquisition rates and a relatively small range differential pressure transducer (+/– 350 mbar) to allow reliable kinetic measurements using mg quantities of sample.

To validate the system we carried out O₂ and N₂ kinetic experiments on Takeda 3K-172 CMS at different pressure levels from 100 mbar to 5 bar using only 40 mg of sample. The results show a complex behavior characterised by a strong concentration dependence of the time constant with a clear transition between transport mechanisms.

1. Brandani, E. Mangano, F. Brandani, P. Pullumbi. Carbon dioxide mass transport in commercial carbon molecular sieves using a volumetric apparatus, Sep. Purif. Technol. (245), 2020.
2. Y. Wang, E. Mangano, S. Brandani, F. Brandani, P. Pullumbi. A novel adsorption differential volumetric apparatus to measure mass transfer in nanoporous materials, Sep. Purif. Technol. (283), 2022.