(548c) Mass Transfer Rates of Argon, Oxygen, and Nitrogen in Carbon Molecular Sieve Measured by Pressure-Swing Frequency Response

The adsorptive separation of air into pure gases is complicated by similarities in isotherms for oxygen and argon on many adsorbents. Molecular sieves separate gases based on differences in effective molecular size, and thus have promise for separating oxygen and argon.  In this work, mass transfer of the three main atmospheric gases (N₂, O₂, and Ar), has been studied in a carbon molecular sieve (CMS) material using pressure-swing frequency response. Pure gases were studied at pressures ranging from 0.125-1 bar over the frequency range from 2·10^-5 to 0.2 Hz. Measured frequency response spectra are compared with both the linear driving force model (corresponding with a surface barrier resistance) and a micropore diffusion model. Relevant model parameters are reported. The experimental results show that oxygen diffuses through the CMS much more quickly than the other two gases, with argon being the slowest of the three. These results suggest that this CMS material could be used as part of a process designed to generate a high-purity oxygen product from air.