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The growth of a silicalite-1 coating on ZSM-5 zeolite crystals is one of the surface modification methods allowing to improve its catalytic p-xylene selectivity. Aiming to understand this increase in p-xylene selectivity, the effect of silicalite-1 coating on the adsorptive properties of ZSM-5 was investigated. Pulse chromatographic experiments revealed the silicalite-1 coating improved the separation factors of p-xylene over o-xylene and m-xylene, resulting in a better chromatographic separation of p-xylene over m-xylene on silicalite/ZSM-5 compared to that on parent ZSM-5. Additionally, slower adsorption kinetics of mxylene on silicalite/ZSM-5 compared to ZSM-5 was also confirmed by gravimetric adsorption measurements. It is concluded that the enhanced p-xylene selectivity is achieved by steric effects leading to a more pronounced exclusion of m-xylene in the outer silicalite-1 layer and a reduction in number of surface adsorption sites.

Fisher esterification of acetic acid (or acetic anhydride) with ethanol (EtOH) is the main industrial process for the synthesis of ethyl acetate (EA). Nonetheless, the separation of the produced ester from ethanol is challenging since these volatile organic compounds (VOCs) form an azeotropic mixture. In this work, the adsorption and separation EtOH/EA/water mixtures on the ZIF-8 metal−organic framework is studied. The present study aims to characterize the adsorptive behavior of ZIF-8 with non-ideal EtOH/EA/ water mixtures. Single and multicomponent adsorption isotherms, obtained by gravimetry and breakthrough experiments, show high adsorption capacity and selectivity toward ethyl acetate. Pulse chromatography experiments confirm the higher interaction strength between EA and ZIF-8 in the low-pressure range at a low degree of pore filling (Henry's region). The breakthrough profiles show development of intermediate plateaus in specific concentration ranges, with complex breakthrough evolution that has been modeled using a combined ideal and real adsorption solution theory model to accounts for deviations from ideality.

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