FREQUENCY-RESPONSE STUDY OF SINGLE-FILE DIFFUSION IN THETA-1

Diffusion of nitrogen, carbon monoxide and carbon dioxide molecules in theta-1, a zeolite with a one-dimensional 10-ring channel network, ha s been investigated using the frequency response (FR) method. Surface barrier effects have been observed from the frequency response spectra in theta-1, where single-file diffusion may apply. The temperature an d concentration dependences of diffusion coefficients and surface barr iers have been discussed. The diffusivities and activation energies of CO and CO2 diffusion in theta-1 determined by FR method are compared with those measured by the FR and pulsed field gradient (PFG) NMR meth ods in silicalite-1 which has 10-ring pores which, however, are inters ected.