Title:
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Screening, developing and testing metal-organic frameworks for industrially relevant CO/N2 separation
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The demands to reduce the energy consumption and expenditure of industrial chemical separation processes provide great opportunities to develop and apply new technology and materials. As carbon monoxide (CO) is not a natural resource, its requirement for purification is important for its utilisation as a large-scale chemical reagent. Nitrogen (N2) impurity from the syngas source poses difficult separation challenges, which current CO purification technologies are trying to overcome to reduce capital and operating costs. Adsorption separation is an avenue that has the ability to improve the efficiency of this challenging separation, with metal-organic frameworks (MOFs) highlighted as a class of porous materials to achieve this. However, the number of studies on CO separation using MOFs that mimic industrial conditions remain scarce. This thesis presents an in-depth study of MOFs for CO/N2 separation with an industrial outlook, using tailored screening, design, synthesis, characterisation and testing of MOFs. An initial testing screening procedure found two MOFs to be the best performing for CO/N2 separation; Ni-MOF-74 and Co-MOF-74. Further in-depth testing was performed on these MOFs, studying the effect of N2 and CO2 impurity levels and recyclability under dynamic conditions. Dynamic testing of related structures provided greater insight into the role of the MOFs metal sites and porosity. These dynamic measurements also contributed useful kinetic data for future development of process scale modelling. Using the knowledge gained from the preliminary screening and in-depth testing, the CO/N2 separation performance of M-MOF-74 was enhanced by post-synthesis chemical modification (i.e. addition of Cu+ sites). Overall, this thesis assesses and improves the industrial viability of MOFs for CO/N2 separation.
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