The single-step frequency-response technique, and the full frequency-response method, were used to monitor the diffusion of benzene in HZSM-5, silicalite-I, and NaX zeolites. The diffusivities of benzene, ethylbenzene, p-xylene and o-xylene in silicalite at 373K were 3.1 x 10-9, 2.0 x 10-9, 2.9 x 10-9 and 1.2 x 10-9m2/s, respectively. The diffusivities of benzene in HZSM-5 were found to be a factor of 2 to 3 smaller than those in silicalite-I. Both diffusivities at 400K were in close agreement with previously published diffusivities of about 10−13m2/s. In the more open channel structure of NaX, the diffusivity of benzene at 450K was about 10−10m2/s; three orders of magnitude greater than in the pentasils.

Diffusivities of Benzene in HZSM-5, Silicalite-I, and NaX Determined by Frequency-Response Techniques. D.Shen, L.V.C.Rees: Zeolites, 1991, 11[7], 666–71