Rotation of propane molecules in supercages of Na-Y zeolite

Rotational dynamics of propane in Na-Y zeolite at room temperature is studied by molecular dynamics (MD) simulations and quasi-elastic neutron scattering (QENS) measurements. It is found that propane undergoes very fast rotational motion in the cages of Na-Y zeolite as first observed in the MD study and later confirmed by the QENS measurements. The dynamics of propane is described by isotropic rotational diffusion on a sphere of radius 1.88 ( +/-0.05) Angstrom, which is also the average distance of the hydrogen atoms from the center of mass of the propane molecule. The rotational diffusion constant as obtained from the QENS and MD simulation is in close agreement. This is the first ever study of the rotational dynamics of propane in a zeolite. (C) 2003 Elsevier Science B.V. All rights reserved.