Adsorption of xylenes on faujasite-type zeolite: Equilibrium and kinetics in batch adsorber

The adsorption of p-xylene, o-xylene and ethylbenzene on ion-exchanged fuajasite type zeolite has been studied in liquid phase at 30, 50, 80, 120 and 180°C. The single adsorption isotherms have been measured in a batch mode. The Langmuir and Sips isotherm have been used to describe the experimental adsorption isotherm data. The Sips equation fits the experimental isotherm data better than the Langmuir model. The saturation adsorption capacity of the adsorbent was similar for all components (around 1 mol kg^-1). The p-xylene is the more strongly adsorbed component followed by ethylbenzene and o-xylene. The heat of the adsorption was 27.2 kJ/mol^-1 for p-xylene, 20.3 kJ/mol^-1 for ethylbenzene and 18.5 kJ/mol^-1 for o-xylene. The kinetics of adsorption of p-xylene, o-xylene and ethylbenzene was also studied. The xylene uptake curves have been described by a mathematical model that accounts for the macropore and/or micropore diffusion as rate controlling mechanisms. It was found that, for temperatures lower than 80°C in the case of p-xylene and lower than 50°C for o-xylene and ethylbenzene, both macropore and micropore diffusion contribute to the rate of adsorption. At higher temperatures macropore diffusion is the rate-controlling mechanism.