chapter  7
28 Pages

7Characterization of Macroscopically Nonhomogeneous Porous Media through Transient Gas Sorption or Permeation Measurements

ByJ.H. Petropoulos and K.G. Papadokostaki

In porous adsorbent/catalyst pellets or separation membranes (barriers), nonhomogeneitymaybeintroducedeitherdeliberately(laminates,“asymmetric”membranes)orspuriously(e.g.,“skinlayers”onpowdercompactsor extrudedpellets),leadingineachcasetocorrespondingspatialdependence oftherelevantgassorptionanddiffusioncoef„cients,SandDT, which are de„nedhereasfollows(PetropoulosandRoussis1967a,b;Petropoulos1985):

S C a= / (7.1)

CONTENTS

7.1 Introduction ................................................................................................253 7.2 Steady-State Permeability Properties ...................................................... 255

7.2.1 Concentration-Independent Systems ..........................................255 7.2.2Concentration-Dependent Systems .............................................255

7.3 Permeation Time Lags (Concentration-Independent Systems) ...........256 7.3.1 Sorption and Permeation Apparatus for a Gaseous