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Physical Adsorption Analysis of Intact Supported MFI Zeolite Karl D. Hammond, Geoffrey A. Tompsett, Scott M. Auerbach,*,, and
 

Summary: Physical Adsorption Analysis of Intact Supported MFI Zeolite
Membranes
Karl D. Hammond, Geoffrey A. Tompsett, Scott M. Auerbach,*,, and
W. Curtis Conner, Jr.*,
Department of Chemical Engineering, 159 Goessmann Laboratory, UniVersity of Massachusetts, Amherst,
Massachusetts 01003, and Department of Chemistry, 701 Lederle Graduate Research Tower,
UniVersity of Massachusetts, Amherst, Massachusetts 01003
ReceiVed NoVember 7, 2006. In Final Form: March 1, 2007
We compare the adsorption properties of intact supported silicalite membranes with those of silicalite powder and
of alumina supports using nitrogen and argon as adsorbates at 77 K. We disentangle contributions from the membrane
and support and find that the support contributes significantly to the total quantity adsorbed due to its relative thickness.
The micropore-filling regions of the adsorption isotherms of the powder and the supported membrane are nearly
identical for the membranes studied, but the isotherms differ at higher pressuressthe supported membranes exhibit
a much higher quantity adsorbed than the powders. Despite this difference, no hysteresis is observed in the membrane
isotherms, indicating a lack of mesoporosity (pores in the 2-50 nm range) in either membrane or support for this
preparation. We estimate argon transport fluxes at steady state by assuming surface diffusion with both a constant
and concentration-dependent Maxwell-Stefan diffusion coefficient in the zeolite and the support. Further, we use
the respective adsorption isotherms to determine the thermodynamic correction factorssthat is, the ratios of the Fick
and Maxwell-Stefan diffusion coefficientssrequired to solve the diffusion equation. The estimated argon flux is
virtually the same using adsorption data from powders and membranes. For the relatively thick supports used in our

  

Source: Auerbach, Scott M. - Department of Chemistry, University of Massachusetts at Amherst

 

Collections: Chemistry