Adsorption and separation of xylene isomers vapors onto the chromium terephthalate-based porous material MIL-101(Cr): An experimental and computational study

The adsorption of the xylene mixture onto MIL-101(Cr) has been studied experimentally and theoretically. The adsorption isotherms of the xylene isomers show a high affinity for each isomer with MIL-101(Cr). This is in good agreement with the enthalpies of adsorption extrapolated at zero coverage, -75 kJ mol(-1), -68 kJ mol(-1) and -64 kJ mol(-1) for o-, m- and p-xylene respectively. The order of these values is consistent with that obtained by the computer simulations. The saturation plateau obtained with p-xylene is higher than that obtained with the adsorption of o- or m-xylene onto MIL-101(Cr). This was discussed in terms of stacking in the cavities of MIL-101(Cr). The filling of the small cavities of MIL-101(Cr) was found more difficult in the case of m-xylene which was interpreted by a weaker interaction with the cavities walls. The chromatographic separation of the xylene mixture was consistent with these results. Different retention times could be found, agreeing the different enthalpies of adsorption for the different isomers. o-Xylene was successfully separated from the xylene mixture. (C) 2013 Elsevier Inc. All rights reserved.