A comparative study of diffusion of benzene/p-xylene mixtures in MFI particles, pellets and grown membranes

R. Kolvenbach, N. Al-Yassir, S. S. Al-Khattaf, O. C. Gobin, J. H. Ahn, A. Jentys, J. A. Lercher

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

The transport and separation of mixtures between benzene and p-xylene in pellets prepared by pressing of ZSM-5 powder and a dense supported (crystalline) Silicalite-1 membrane were compared to isolated ZSM-5 crystallites. The kinetics of the transport in the pressed pellet and the grown membrane determined in a Wicke-Kallenbach cell (313-403 K; partial pressure range 200-2300 Pa) differed significantly from those measured for isolated ZSM-5 particles with the pressure modulation frequency response technique (343-403 K; partial pressure 30 Pa). In a pressed pellet, the transport was of Knudsen type leading to high fluxes of 10-4 mol/m2 s and identical permeances for benzene and p-xylene. The diffusion coefficient in a pressed pellet exceeded that in particles, in which the transport was controlled by intracrystalline diffusion and the pore entrance step, by 8 orders of magnitude. The flux across a grown Silicalite-1 membrane was two orders of magnitude lower and the permeability of p-xylene was 2.6-5 times higher than that of benzene. The change in diffusivity in the membrane compared to the particles results from the higher surface coverage of p-xylene.

Original languageEnglish
Pages (from-to)147-157
Number of pages11
JournalCatalysis Today
Volume168
Issue number1
DOIs
StatePublished - 20 Jun 2011

Keywords

  • Aromatic molecules
  • Knudsen diffusion
  • Pressure modulation frequency response
  • Silicalite-1 membranes
  • Stefan-Maxwell diffusion
  • Wicke-Kallenbach experiments
  • ZSM-5

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