Liquid-Phase Multicomponent Adsorption and Separation of Xylene Mixtures by Flexible MIL-53 Adsorbents

Mayank Agrawal, Souryadeep Bhattacharyya, Yi Huang (Lead Author), Krishna C. Jayachandrababu, Christopher R. Murdock, Jason A. Bentley, Alejandra Rivas-Cardona, Machteld M. Mertens, Krista S. Walton, David S. Sholl, Sankar Nair

Research output: Contribution to journalArticlepeer-review

Abstract

The MIL-53 class of metal-organic frameworks (MOFs) has recently generated interest as potential adsorbents for xylene mixture separations. Cost-effective separation of xylene isomers is challenging owing to the similarity in their molecular structures, kinetic diameters, and boiling points. Here we report a systematic experimental and computational study of xylene isomer adsorption in MIL-53 adsorbents, focusing particularly on the effects of different metal centers, determination of separation properties with industrially relevant quaternary liquid-phase C8 aromatic feeds, and a predictive molecular simulation methodology that accounts for all relevant modes of MIL-53 framework flexibility. Significant scale-up of MIL-53 synthesis was carried out to produce high-quality materials in sufficient quantities (300-500 g each) for detailed measurements. Single-component adsorption simulations incorporating the MIL-53 "breathing" and linker flexibility effects showed good agreement with experimental isotherms. Upon the basis of these results, three materials - MIL-53(Al), MIL-53(Cr), and MIL-53(Ga) - were selected for detailed quaternary liquid breakthrough measurements. High o-xylene quaternary selectivity was obtained from all of the MIL-53 materials, with MIL-53(Al) being the most selective. Better packing efficiency of o-xylene and its preferred interactions with the MIL-53 framework are hypothesized to lead to high selectivity. Predictions from flexible-structure multicomponent adsorption simulations showed good overall agreement with experiment. This is, to the best of our knowledge, the first experimental report on the xylene adsorption characteristics of MIL-53 materials under industrially relevant operating conditions. In addition, it is also the first attempt to develop computational methods that account for various flexibility modes in MIL-53 materials for adsorption simulations. This has significant broader applications for the successful prediction of adsorption properties of larger molecules (such as C8 aromatic isomers) in flexible MOFs.

Original languageEnglish
Pages (from-to)386-397
Number of pages12
JournalJournal of Physical Chemistry C
Volume122
Issue number1
Early online date12 Dec 2017
DOIs
Publication statusE-pub ahead of print - 12 Dec 2017
Externally publishedYes

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