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  • Author or Editor: J. P. Bellat x
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Abstract  

The derivative enthalpies of adsorption of m-xylene and p-xylene onto the NaY and BaY zeolites were measured at 150°C, then compared with those obtained at 25°C, and finally used to predict the selectivity of adsorption of xylene mixtures. Significant differences were observed as the temperature was elevated: for the NaY zeolite, the adsorbate-adsorbate interactions became prevalent, in contrast with the BaY zeolite, between zeolite and derivative interactions were stronger. The difference between the adsorption derivative enthalpies of the two xylenes displayed an abrupt variation from 2 molec. –1 for both zeolites, the filling from which selectivity towards m-xylene for the NaY zeolite and towards p-xylene for the BaY zeolite appeared. The preferentially adsorbed xylene was closely connected with the sense of this difference, which changed with the zeolite.

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The differential enthalpies of adsorption ofp-xylene andm-xylene on NaY, KY and BaY zeolites were measured by isothermal calorimetry coupled with isothermal volumetry at 25‡C. Whatever the zeolite, the enthalpies of adsorption ofp-xylene andm-xylene at low filling were of the same order of magnitude. They did not show significantly the effect of the dipolar moment ofm-xylene. Their absolute values varied in the sequence

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Abstract

The adsorbed amounts of water vapor onto polyacrylic polymer (polymer ×10) were measured using a thermogravimetry method as a function of pressure at 298 and 313 K. The adsorption isotherms are categorized to type II isotherms by IUPAC classification leading to a hysteresis loop between adsorption and desorption branches. The current study was completed by the measurement of the adsorption heats at 298 K using a differential scanning calorimetry. The calorimetric curves showed two adsorption heats domains. These domains have been attributed to the adsorption of “equivalent monolayer” and the condensation of water between polymeric chains. The correlation of experimental data to some chosen theoretical models shows that the GAB model is the most adequate to describe water vapor sorption isotherms.

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