Diffusion of benzene in NaX zeolite, studied by thermal frequency response

The thermal frequency response technique (TFR) has been used to study the d iffusion of benzene in NaX zeolite. The corrected diffusion coefficient is found to be independent of loading between 1.5 and 3.6 mol/cage at 406 K. I t is in reasonable agreement with pulsed-field gradient NMR or quasi-elasti c neutron scattering methods, but a large discrepancy is observed with the tracer zero length column (TZLC) technique. The activation energy for diffu sion determined by TFR, 27 kJ/mol, is in accordance with the TZLC value, bu t substantially higher than the values reported from the other techniques.