It was recalled that, for the study of diffusion in microporous crystalline materials with 10MR/12MR interconnected channels, such as H-CIT-1, para- and ortho-xylene were excellent probes. Using FTIR techniques, co-diffusion and counter-diffusion of these isomers were studied (tables 13 and 14). The values of the diffusivities in co-diffusion and counter-diffusion experiments were determined. A correlation in the transport of both isomers was observed for co-diffusion and counter-diffusion. During co-diffusion, the more mobile p-xylene molecule hindered the motion of o-xylene. During counter-diffusion, when p-xylene diffused-in and o-xylene diffused-out, the 10MR channels, which were blocked to o-xylene molecules, were open to p-xylene motion. Molecular traffic control subsequently occurred.

Codiffusion and Counterdiffusion of Para-Xylene and Ortho-Xylene in a Zeolite with 10MR/12MR Interconnected Channels. An Example of Molecular Traffic Control. R.Roque-Malherbe, V.Ivanov: Journal of Molecular Catalysis A, 2009, 313[1–2], 7–13

Table 13

Co-Diffusion of Xylenes in H-CIT-1