Using Fourier transform infra-red spectroscopy, the intrinsic diffusion coefficients of benzene, toluene, ethylbenzene, m-xylene and o-xylene in H-ZSM-5, H-Beta and H-MCM-22 were measured at various temperatures. By assuming a microscopic model for molecular diffusion in zeolites, and invoking transition-state theory, the self-diffusion coefficients of molecules in zeolites with straight channels were calculated (table 12).

Diffusion of Aromatic Hydrocarbons in H-ZSM-5, H-Beta, and H-MCM-22 Zeolites. R.Roque-Malherbe, R.Wendelbo, A.Mifsud, A.Corma: Journal of Physical Chemistry, 1995, 99[38], 14064–71

Figure 8

Characteristic Time for Intra-Particle Diffusion in Beta Zeolite

(White circles and solid line: isobutene,

black circles and dashed line: n-butane)

Table 12

Diffusivity of Aromatic Hydrocarbons in Zeolites at 350K