Separation of ternary hydrocarbon mixtures on Y zeolite membranes

Abstract

The permeation of a mixture of n-hexane, n-decane and toluene through a 40 μm Y zeolite tubular membrane on a support with negligible resistance to the mass transfer at 250 °C was modelled based on the Maxwell-Stefan formulation and the ideal adsorbed solution theory (IAST). Individual adsorption parameters were obtained with a batch fluidized bed reactor and diffusion parameters were taken from the literature. The model allowed to predict the transient fluxes and surface coverages through the membrane, showing that the responses of the components diffusing faster (n-hexane and n-decane) overshoot their steady-state values. The permeance predictions (10-8 mol/s m2 Pa) ranged from 1.2 to 20 for n-decane, from 0.4 to 4.2 for n-hexane and from 0.8 to 4.0 for toluene, according to the feed pressure and composition. The permeance selectivities, defined with n-hexane as the reference, ranged between 3 and 6 for n-decane, and between 1 and 1.8 for toluene. It was also possible to define the association between hydrocarbon coverage profiles in the membrane and the corresponding resulting fluxes.