Date of Award

2018

Degree Type

Thesis

Degree Name

Master of Science in Chemical Engineering

Department

Chemical and Biomedical Engineering

First Advisor

Gumma, Sasidhar

Subject Headings

Chemical Engineering

Abstract

Metal organic frameworks (MOFs) are highly porous solids with potential applications in a wide range of fields including gas separations and catalysis. Most of porous solids used in these applications such as zeolites and activated carbon usually have rigid structures. In contrast, a number of metal-organic frameworks (MOFs) exhibit structural transformation in response to external stimuli. Such materials show promise for applications such as sensors, actuators and adsorptive separations. Several thermodynamic formalisms were proposed in literature to explain this phenomenon, often known as gate-opening or “breathing” of the MOF material. In this study, the adsorptive behavior of MIL-53(Al), a MOF that undergoes a change in volume of about 40% when transiting between its narrow pore (np) and large pore (lp) phases was measured. The binary adsorption characteristics of this MOF depend on its history, which makes these experimental measurements and its modeling more complicated. In literature, mixed gas adsorption equilibrium data on this material is limited to CO2/CH4 mixtures. Moreover, available models in literature cannot describe the history dependence of equilibrium data for gas mixtures. The pure component adsorption equilibria at 293 K on the narrow pore phase showed a significantly higher capacity for CO2 (compared to that of N2) in the sub-atmospheric pressure region. In addition, the binary adsorption equilibria results showed that the narrow pore phase exhibited a high CO2/N2 selectivity, while the selectivity was close to unity on the large pore phase. The pure component isotherms on this material were modeled using a Langmuir type isotherm for each phase that includes a pore opening parameter dependent on spreading pressure (SPDPLM Model), as proposed in literature. In addition, for the first time in this work the SPDPLM was readily extended to binary mixtures, without any additional parameters.

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