This thesis is mainly concerned with the study of solvents of relevance for carbon capture and storage (CCS). The current industrial approach relies on amines to capture CO2, however this thesis describes a range of alternative non-amine based solvents, particularly phenols, saturated and unsaturated aliphatic acids, long chain fatty acids, aromatic acids, and β-dicarbonyl compounds (mainly ketones and esters). The CO2 capture capacities of these substrates have been compared with the industrial model substrate (monoethanolamine, MEA). From this study, phenols show 49-90% CO2 capture capacity whereas aromatic phenolic acids such as gallic acid show up to 100% theoretical CO2 capture capacity. Acetylacetone, a β-diketone shows 88% and the rest of the substrates from this and other groups show 50-60% CO2 capture capacity. However, some of the substrates, particularly simple mono and polycarboxylic acids showed negligible CO2 capture capacity, which can be understood on the basis of pKa. Particular attention has been paid to understanding the formation of bicarbonate salts, which would be expected under aqueous conditions. Clear evidence for their formation is provided by 13C NMR studies. The measured CO2 capture capacities of the new substrates have been correlated with pKa values. Those with pKa values between 9-13 have excellent to good CO2 capture capacity whereas others having pKa < 7, have insignificant CO2 capture capacity. The substrates with low pKa capture less volume of CO2 compared to those having high pKa, but release it more easily on heating. The second body of work is a study on the chemistry of MEA and its oxidised derivatives. MEA is currently the industry standard for CO2 capture. Given that power station flue gases contain large amounts of oxygen, and trace metals which may act as oxidation catalysts, understanding the chemistry of oxidised MEA derivatives is of increasing importance. This can have a significant effect on solvent activity and lifetime, which are important aspects of the economic profile of CCS. MEA was oxidised under a variety of conditions, and a complex mixture of products was formed. Many of these have been unambiguously identified by comparison with commercial or synthetic samples. The main oxidation products were then heated at 100°C for prolonged periods of time to mimic conditions in a commercial CCS system. Thermal degradation of MEA oxidation products was clearly observed, and in some cases, could be rationalised on the basis of established organic reactivity.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:713474 |
| Date | January 2013 |
| Creators | Bala, Shashi |
| Publisher | University of Leeds |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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