Abstract
The calculated micropore size of various molecular sieves has been examined using static argon porosimetry and a simple model for adsorption. The molecular sieves used in this study are NaY, ZSM-5, AlPO 4-5, AlPO 4-11 and VPI-5. Since zeolites and aluminophosphates have different interactions with argon, a lumped parameter for adsorptive interactions was found to be critical to the evaluation of micropore size using an area-averaged cylindrical pore model. The parameter of choice is the magnetic susceptibility of the adsorbent oxide ion. For NaY and ZSM-5, a magnetic susceptibility of χ=−1.3·10 −29cm 3 shows good results. With a value of χ=−1.9·10 −29cm 3, the calculated pore sizes of AlPO 4-5 and AlPO 4-11 are in good accord with the values from X-ray diffraction studies. For VPI-5, which has a larger pore, the monolayer cylindrical pore model is more adequate, but it requires inclusion of an adjustable factor to compensate for adsorbate-adsorbate interactions.
Published Version
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