Molecular dynamics of xylene in Na, Yb-Y and ZSM-5 studied by quasi-elastic neutron scattering

Abstract

The quasi-elastic neutron scattering of xylene adsorbed in Na, Yb-Y and ZSM-5 has been studied in the temperature range 100–460 K. In both zeolites the translational motion is too slow to be observed on the timescale of the experiment so that only the rotational motions can be characterized. At 100 K only the methyl groups are rotating for xylene in Na, Yb-Y and with increasing temperature a uniaxial rotation of the whole molecule sets in. For high loadings of p-xylene in Na, Yb-Y the amplitude of oscillation remains at lower values at the same temperature as for the low loadings, indicating molecule–molecule interactions. The experimental elastic incoherent structure factors (EISFs) of p-xylene in ZSM-5 do not vary over the whole examined temperature range, the aromatic ring stays fixed and only one of the methyl groups is rotating.