Single-and multicomponent sorption/diffusion of hydrocarbons from their iso-octane solution in H-ZSM-5 zeolite

Abstract

Single- and multicomponent sorption/diffusion of hydrocarbons (viz. n-hexane, toluene, p-xylene, n-propyl benzene and iso-propyl benzene) from their iso-octane solution in H-ZSM-5 at 288-320 K has been investigated. The influence of a fast diffusing species on the sorption of a slow diffusing species and of other sorption species on the sorption and diffusion of particular sorbate in the zeolite have also been investigated. In the single-component sorption, the uptake rates for toluene and p-xylene are much higher than that for n-propyl benzene, whereas, in the multicomponent sorption, the uptake rates for n-propyl benzene are higher than that for toluene and p-xylene. Also, in the presence of p-xylene, the rate of sorption of n-propyl benzene in H-ZSM-5 is increased very significantly. The sorption rate of a slow diffusing species (e.g. cumene) in the zeolite is drastically reduced in the presence of a fast diffusing species (e.g. p-xylene and n-propyl benzene). In the simultaneous sorption of p-xylene and n-propyl benzene or of toluene, p-xylene and n-propyl benzene, the uptake curves for toluene and p-xylene pass through a maximum indicating that the sorption is kinetically controlled in the initial sorption period and thereafter it is controlled by the sorption equilibrium.