Affordable Access

Publisher Website

Mixture diffusion in zeolites studied by MAS PFG NMR and molecular simulation

Microporous and Mesoporous Materials
Publication Date
DOI: 10.1016/j.micromeso.2007.05.042
  • Mixture Diffusion
  • Zeolites
  • Mfi
  • Fau
  • Butane Isomers
  • Magic Angle Spinning
  • Pulse Field Gradient
  • Nuclear Magnetic Resonance
  • Molecular Dynamics
  • Traffic Junction Effect


Abstract A combination of magic-angle spinning (MAS) and pulsed field gradient (PFG) NMR has been used to determine the self-diffusivities in MFI zeolite of n-butane, D nC4 , in mixtures with iso-butane in which the total loading, q, is maintained constant at 4 molecules per unit cell. When the loading of iC4 in the mixture, q iC4 , is increased from 0 to 2, the diffusivity D nC4 is observed to decrease dramatically by two orders of magnitude. Snapshots obtained from molecular simulations indicate that the iC4 molecules are preferentially located at the intersections between the straight channels and zig-zag channels of MFI; these intersections serve as traffic junctions. At q iC4 = 2, the molecular traffic along the straight channels is brought to a virtual stand-still because of the obstructive influence of slow-diffusing iC4 ensconced at these junctions. Molecular dynamics (MD) simulations of D nC4 in nC4/ iC4 mixtures show good qualitative agreement with the observed experimental results. In sharp contrast, both experimental measurements and MD simulations, of D nC4 and D iC4 in wide pore FAU zeolite yield D nC4 ≈ D iC4 and there is no influence of mixture composition on component diffusion.

There are no comments yet on this publication. Be the first to share your thoughts.


Seen <100 times

More articles like this

New options for measuring molecular diffusion in z...

on Chemical Physics Letters Jan 01, 2005

Ethene/ethane mixture diffusion in the MOF sieve Z...

on Microporous and Mesoporous Mat... Jan 01, 2012

Diffusion of ammonia in silicalite studied by QENS...

on Microporous and Mesoporous Mat... Jan 01, 1998

Diffusion in binary gas mixtures studied by NMR of...

on Physical Chemistry Chemical Ph... Sep 28, 2006
More articles like this..