The zero-length column method was used to study the diffusion of benzene and several linear paraffins in large crystals of silicalite. The zero-length column diffusivity data were broadly consistent with previously reported membrane, piezometric and frequency-response values, but the values for propane were much smaller than the NMR self-diffusivities. The diffusivity of propane in silicalite at 303K was 7.7 x 10-8cm2/s, with an activation energy of 12.97kJ/mol. The diffusivity of pentane at 323K was 1.5 x 10-8cm2/s, with an activation energy of 19.24kJ/mol. The diffusivity of decane at 373K was 3.1 x 10-9cm2/s, with an activation energy of 20.92kJ/mol. The diffusivities of C12 and C20 alkanes at 343K were 2.3 x 10-9 and 2.0 x 10-9cm2/s, respectively, with corresponding activation energies of 19.25 and 18.83kJ/mol. The trends in diffusivity with carbon number for 5A, 13X and silicalite were qualitatively similar, with the diffusivities for silicalite lying between the corresponding values for 5A and 13X. For carbon numbers greater than 5, the activation energies for silicalite were essentially the same as those for NaX.

Intracrystalline Diffusion of Linear Paraffins and Benzene in Silicalite Studied by the ZLC Method. M.Eic, D.M.Ruthven: Studies in Surface Science and Catalysis, 1989, 49, 897–905