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Title: Ionic liquids for carbon dioxide capture
Author: Ng, Shieling
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2013
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The Petronas C02 project aimed to design an ionic liquid-based technology for the removal of C02 from natural gas. Current technology using amine-based system is not economical. It is envisioned that an ionic liquid method has the potential to be superior to current technology, due to their unique characteristics, such as high thermal stability, negligible vapour pressure and the possibility to fine-tune their properties, by combining appropriate cations and anions. This project involved the development of a "simple" synthetic method for ionic liquids, utilising Group 2 metal hydroxides (especially, strontium hydroxide octahydrate). This gave a wide array of carboxylate ionic liquids, via an intermediate hydroxide solution. It is a very simple, straightforward procedure which uses starting materials which are commercially available in bulk. The classes of carboxylate ionic liquids that have been synthesised and fully characterised are those based on the cations: l-ethyl-3-methylimidazolium, tributylmethylammonium, tetraalkylphosphonium and l -al kyl -l-methylpyrrolidinium. The Hunig's based derivatives of l -alkyl•3•methylimidazolium bistriflamides, as well as phosphonium and ammonium caboxylates were tested for their ability ty to absorb C02. In the anhydrous us system, initial screening showed that the most promising anions for C02 solubility are the methanoate and ethanoate. In parallel, it was observed that the C02 solubility in ionic liquids was not greaby the alkyl chain length on cation. The most noticeable effect on C02 capture was the addition of 1 mole of water to the carboxylate ionic liquids. This greatly enhanced the solubility of C02 by an order of magnitude, which is due to a different mechanism of C02 absorption; chemisorption on in the presence of water, instead of physisorption. A mechanism via the formation of hydrogencarbonate has been proposed due to this remarkable ability for C02 capture, which was later proven by other team members. All in all, the system that has been put forward for consideration as a potential C02 absorber in industrial processes within Petronas is the equimolar system of [4441][CH3C02] and water .
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available