Single- and Multicomponent Vapor-Phase Adsorption of Xylene Isomers and Ethylbenzene in a Microporous Metal−Organic Framework

Vapor-phase adsorption of the C8 alkylaromatic components p-xylene (p-x), m-xylene (m-x), o-xylene (o-x), and ethylbenzene (eb) on the three-dimensional microporous metal−organic framework (MOF) Zn(BDC)(Dabco)0.5 (BDC = 1,4-benzenedicarboxylate, Dabco = 1,4-diazabicyclo[2.2.2]octane) was investigated. Single- and multicomponent fixed-bed experiments were carried out at temperatures ranging from 125 to 175 °C and total hydrocarbon pressures up to 0.10 bar. At high pressure, the adsorption capacity for all the components varies from 35 to 26 g/100 gads at 125 and 175 °C. Henry's constants are slightly different for all C8 alkylaromatics, except for o-xylene, which is significantly higher. The adsorption enthalpies at zero coverage for the different isomers ranges from 77.40 (eb) to 79.84 kJ/mol (o-x), indicating that the C8 alkylaromatics have comparable interactions with the framework at the low coverage. On the basis of binary and quaternary breakthrough experiments performed at different hydrocarbon pressures and temperatures, MOF Zn(BDC)(Dabco)0.5 was realized for the efficient and feasible separation of o-xylene from other C8 alkylaromatic components with the selectivity up to 1.88 because of the stronger interactions between o-xylene molecules and the framework and their differential pore-filling and molecular-packing effects confined within nanopores of MOFs.