COMPARISON OF MACROSCOPIC TRANSIENT METHODS TO DETERMINE TRANSPORT-COEFFICIENTS FOR MICROPOROUS SORPTION SYSTEMS

Macroscopic transient methods are analysed with respect to their applicability to the investigation of molecular transport in microporous sorption systems. Various levels of sophistication of data evaluation for non-equilibrium sorption results obtained by means of batch methods are identified and characterized. Special attention is paid to the characterization of Fickian (intracrystalline) diffusion as well as to the identification and quantification of additional rate mechanisms that, in general, may simultaneously occur in molecular sieve systems. A state of the art determination of transport coefficients is exemplified for the system n-hexane/silicalite-I. Its uptake behaviour can be understood by superposition of processes of Fickian diffusion and intracrystalline molecular immobilization/mobilization.