Non-Ideal Behavior in Gas Mixture Adsorption on Tailored Adsorbents
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This dissertation describes investigations of non-ideal behavior arising in adsorption of gas mixtures on tailored metal-organic framework (MOF) adsorbents. This work improves understanding of limitations of the preeminent mixing theory, the Ideal Adsorbed Solution Theory (IAST), through investigation of equilibrium adsorption of various gas mixtures on MOF adsorbents. Tuning of pore chemistry in MOFs was shown to enhance adsorption properties, including at least one case in which a change in orientation of a pendant functional group turned a nearly nonporous material into one of the best carbon dioxide adsorbents tested in this work. Gas mixture adsorption above ambient pressure was tested in this work using the Multi-Component Gas Adsorption System (MC GAS), a custom, automated instrument which was designed, built, and validated in the course of this work. This instrument facilitated an investigation of the limitations of IAST in predicting gas mixture adsorption on several MOFs where energetically heterogeneous adsorbent surfaces and non-ideal interactions between molecules in adsorbed phases caused deviations from ideal adsorption behavior. This dissertation concludes with a synopsis of available experimental methods for measurement of mixed gas adsorption while making recommendations to investigators who may be interested in using these experimental techniques to study adsorption separations.