Distribution of cation in BaX zeolite and mechanism of adsorption and separation for paraxylene

Document Type

Article

Publication Date

12-1-2005

Abstract

BaX zeolite is a good adsorbent for the adsorption and separation of p-xylene in high purity from C8 aromatic isomers in industry. To understand the effect of Ba2+ distribution in X zeolite on its adsorption and separation ability, the structure of two BaX zeolite samples, BaX-I and BaX-II , with different adsorption speed and resolution was determined by polycrystalline XRD with the electronic density function and Rietveld method. The sites of Ba2+ cations were slight different between the two samples. Ba2+ cations mainly located on the S′I sites and SII sites in BaX zeolite. The Ba2+(1) cations, situated at the S′I sites in the beta cage, made the framework of X zeolite more stable. When the occupancy of Ba2+(2) cations at SII sites was 1, and each Ba2+(2) cation polarized two coordinated water molecules, an adsorption force field with D2 symmetry would be generated in the supercage. p-Xylene molecules belonged to the D2h symmetry group, which includes a D2 subgroup. Thus, the BaX zeolite with this adsorption force field could selectively adsorb and separate p-xylene.

Publication Source (Journal or Book title)

Chinese Journal of Catalysis

First Page

655

Last Page

659

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