Effect of preadsorbed water on the adsorption of p-xylene and m-xylene mixtures on BaX and BaY zeolites

被引:28
作者
Moïse, JC
Bellat, JP
机构
[1] Univ Bourgogne, CNRS, Lab Rech React Solides, UMR 5613, F-21078 Dijon, France
[2] Ecole Natl Super Ind Chim, Inst Natl Polytech Lorraine, Lab Thermodynam Milieux Polyphases, F-54001 Nancy, France
关键词
D O I
10.1021/jp0525639
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Adsorption of an equimolar p-xylene/ni-xylene mixture on partially hydrated barium-exchanged X and Y zeolites is studied at 423 K in the pressure range 10(-2)-8 hPa by differential calorimetry coupled with manometry and chromatography. Results are consistent with structural studies and Monte Carlo simulations of the literature. The presence of preadsorbed water in supercages increases the adsorption selectivity toward p-xylene to the detriment of the adsorption capacity and the adsorption affinity, as indicated by a sharp decrease of the Henry constants. However, the coadsorption heats at zero filling are not influenced by the presence of water. Therefore, entropic effects seem to play an important role in the coadsorption process. Two adsorption sites whose energy differs are identified by calorimetry. The more energetic site could correspond to the p-xylene or m-xylene molecule in interaction with the compensation cation located in sites 11 in the supercage, the less energetic to the adsorption of p-xylene molecule in the 12-ring window joining two supercages. The presence of this second site for p-xylene could be at the origin of the selectivity.
引用
收藏
页码:17239 / 17244
页数:6
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