FIXED-BED ADSORPTION SEPARATION OF XYLENE ISOMERS OVER SIO2/SILICALLITE-1 CORE-SHELL ADSORBENTS

Abstract

SiO 2 /Silicalite-1 core-shell material has been demonstrated as potential shape selective adsorbent in gas phase separation of p-xylene from a mixture of p/o-xylene isomers. The core-shell composite comprised of large silica core and thin polycrystalline silicalite-1 shell which was synthesized via a self-assembly of silicalite-1 nanocrystals on core silica surface followed by a secondary seeded growth method. The core materials, SiO 2 used in this study has mesoporosity with an average pore diameter of 60A and hence offers no shape selectivity for xylene isomers. However, the shell, silicalite-1 contains rigid pore structures and preferentially adsorbs p-xylene from their isomers mixtures. A series of adsorption fixed bed breakthrough adsorption/desorption experiment was performed to obtain the equilibrium isotherms and adsorption isotherm parameters of xylene isomers. The equilibrium isotherms of xylene isomers follow the Langmuir’s model. A chromatographic adsorption model has been used to describe the fixed-bed breakthrough profiles of xylene isomers. The model has successfully predicted the responses of the binary mixtures of p/o-xylene isomers. The SiO 2 /silicalite-1 core-shell adsorbents have shown para-selectivity as high as 15. DOI: http://dx.doi.org/10.3329/cerb.v16i1.17470 Chemical Engineering Research Bulletin 16(2013) 1-15