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Title: Microporous adsorbents for trapping of gaseous pollutants
Author: Saxton, Carl Graham
ISNI:       0000 0001 3554 4655
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2008
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Adsorption studies (xenon and iodine) in microporous materials have been carried out on various materials such as zeolites (FAU, MFI, SAV and CHA) and metal-organic frameworks (MOF-5, HKUST-1 and JUC-32). The as-synthesised and commercial zeolites containing Na+, Li+ or K+ cations and then subsequently ion-exchanged for other extra framework cations. The xenon adsorption in zeolites was interpreted using isosteric heats of adsorption (CHA) and also 129Xe NMR (FAU). CHA type zeolites show a high affinity and capacity for xenon at low xenon pressures <10kPa. This affinity changes depending upon the extra framework cation present due to the positioning and size of the cation. The electric field gradient was a primary factor in the xenon adsorption since a neutral framework (ALPO-CHA) was found to have a lower affinity for xenon but having the same framework type. This was further highlighted by the introduction of Si into the framework and a comparison was made between the three structures CHA, ALPO-CHA and SAPO-34 with the latter being a silicon substituted aluminophosphate carrying a slightly negatively charged framework. Another framework studied was that of STA-7 (SAV) and it was found that varying the silicon within the framework had an effect upon the xenon adsorption. Xenon interaction with the MOFs was minimal when compared to the zeolites. MOF materials adsorbed more iodine per gram of material than any of the zeolites studied. In some materials, two different species of iodine exist. These species, I2 (isolated) and (I2)n (wires) have different Raman frequencies and the (I2)n species have been observed in MOFs for the first time.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available