New Pressure, Volume, and Concentration Swing Frequency Response Apparatus for Measurement of Mass Transfer Rates In Adsorbents

Frequency response methods are unique in their ability both to distinguish mass transfer mechanisms and to determine related parameters for mass transfer of gases in adsorbents.  A new frequency response apparatus, which is able to perform pressure-swing frequency response (PSFR), volume-swing frequency response (VSFR), and concentration-swing frequency response (CSFR) experiments, has been developed to study mass transfer mechanisms and related rates for adsorption systems. Though PSFR and VSFR are similar, it is nevertheless advantageous to combine both techniques to allow studies covering a broader range of the frequency spectrum compared to stand-alone PSFR or VSFR. Combining PSFR and VSFR, the new apparatus can easily cover the range of frequencies from 10^-5 to 10 Hz. This extension makes the new method a good candidate for studying mass transfer rates in new materials, such as MOFs and mesoporous materials, in addition to nanoporous materials.  Mass transfer of CO₂ in NaX zeolite is considered as an example system.