QUASI-ELASTIC NEUTRON-SCATTERING STUDY OF THE DYNAMICS OF METHANE ADSORBED IN NA-MORDENITE

The dynamics of methane adsorbed at different loadings and temperature s in Na-mordenite have been studied by quasi-elastic neutron scatterin g. Two methane species have been characterized: molecules diffusing in the straight channels, and molecules trapped in the side pockets. For an average loading of 0.8 molecule per unit cell, the proportion of m obile molecules in the channels is approximate to 35%. There is an equ ilibrium between the two species depending on the loading and temperat ure. The self-diffusion coefficient is of the order of 10(-9) m(2) s(- 1). This value is smaller than in the MFI or FAU structures because of the trapping in the side pockets.