DIFFUSION OF P-XYLENE IN SINGLE AND BINARY-SYSTEMS IN ZEOLITES INVESTIGATED BY FTIR SPECTROSCOPY

A novel method based on Fourier transform infrared spectroscopy (FTIR) is applied to study sorption and sorption kinetics of p-xylene in ZSM-5-type zeolites as a single component and in a binary-component system, in the presence of benzene under conditions close to those of a catalytic run. From the change of intensities of IR bands characteristic for the adsorbates, diffusivities of p-xylene in the single-component system as well as in the binary-component system are determined at various temperatures and loadings. In comparison with benzene measured as a single component in the same system, the diffusivities of p-xylene are higher by a factor of 2 to 3. This is in agreement with the literature data. In the binary system, the presence of benzene reduces the diffusivities of p-xylene by 30 to 50%. Isotherms, isosteres and isosteric heats of adsorption are determined from the measurements. The isosteric heats of adsorption agree well with the literature data.