Thermal frequency response method for the study of mass‐transfer kinetics in adsorbents

The frequency response method measuring the temperature and pressure of an adsorbent sample determines the mass‐ and heat‐transfer kinetics in adsorbents, especially in zeolites. The temperature of the sample (large crystals or monolayers of pellets) is measured by infrared detection. The main aspects of the in‐phase and out‐of‐phase functions as given by an analytical bidispersed model are described. They depend on characteristic times related to kinetic paprameters. Experimental results on adsorption of water on NaX zeolite (crystals or pellets) show that this method allows heat transfer to be very clearly delineated from mass‐transfer modes and the separation of different mass‐transfer modes. For a bidispersed sample, macro‐ and microporous mass‐transfer parameters may be obtained with the same sample. Results on a contaminated 5A zeolite‐propane system show the presence of mass‐transfer resistance at the pellet surface. The infrared temperature measurement associated with the frequency response appears to be powerful in determining kinetic adsorption, and gives more information than the pressure measurement.