Equilibrium and kinetics of<i>n</i>– hexane sorption in pellets of 5A zeolite

Abstract

Abstract Equilibrium, diffusion, and fixed‐bed adsorption of n‐hexane in pellets of 5A zeolite (Rhone‐Poulenc) were studied between 373 and 573 K and at partial pressures up to 0.2 bar. Equilibrium data were obtained in a flow microbalance system. Diffusivity was studied simultaneously by gravimetric and ZLC techniques. Adsorption isotherms were satisfactorily described by a localized adsorption model developed by Nitta et al. (1984) with only one temperature‐dependent parameter (coefficient of Henry's law). The isosteric heat of adsorption is 14.2 kcal/mol.Kinetic data clearly show that macropore diffusion is the controlling mass‐transfer mechanism. Between 473 and 573 K, pore diffusivities range from 0.11 to 0.13 cm 2 /s in the system He‐nC 6 , and from 0.06 to 0.08 cm 2 /s in the system N 2 C 6 . The effect of partial pressure of sorbate, temperature, and total flow rate in the behavior of the fixed‐bed unit is shown. A simple mathematical model with equilibrium and diffusivity parameters obtained in this work predicts with good accuracy all fixed‐bed adsorption experiments.