Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.578710
Title: The capture and activation of CO2 for the production of sustainable chemical feedstocks
Author: Supasitmongkol, Somsak
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2011
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Abstract:
With the considerable increase in both the consumption and demand of fossil fuels, carbon dioxide emissions in the atmosphere will increase correspondingly, causing global warming. However, carbon dioxide (C02) as a chemical has many advantages chemically; it is non-toxic, non-combustible, and can also be the starting material for the synthesis of fine chemicals. Among the possible processes which utilise carbon dioxide as a reagent, the synthesis of five-membered cyclic carbonates is very appealing, due to their vast potential for use as polar solvent, chemical intermediates and monomers in polymerisation. Therefore, this research aims to capture and activate carbon dioxide to produce cyclic carbonates. Carbon dioxide absorption III several imidazolium-based IOnIC liquids, pyridinium-based ionic liquids, and a tetramethylammonium-based ionic liquid, poly[ (p-vinylbenzyl)trimethylammonium hexafluorophosphate] (P[[VBTMA] [PF 6]]) and its monomer was studied in comparison with glycerol trioctanoate and powdered materials (such as hydrota1cites, mixed oxides and boehmite). The thermal stability, long-term stability, decomposition kinetics and the evaporation of ionic liquids were also investigated. The influence of many parameters on sorption capacity such as sorption isotherm, stability on cycle operation, gas selectivity and sorption kinetics of samples were considered in this research. Bench-scale CO2 capture was also carried out to determine the thermodynamic properties and energy required for CO2 absorption and desorption. The results show that the highest thermal stability was exhibited by the imidazolium cation and bis(trifluoromethylsulfonyl)imide anion, compared with the other ionic liquids studied. All the ionic liquids studied can have a detectable vapour pressure in the temperature range 80-120 °C as determined by thennogravimetric analysis. The functional groups of the ionic liquids had strong effects on CO2 sorption capacity and selectivity. The largest effect on CO2 solubility was associated with the ionic liquid anion. The activation energy values of CO2 sorption mainly arise from the different viscosities in all the ionic liquids, whereas those of the poly(ionic liquid) and ionic liquid monomer mainly depend on the morphological structure. The lowest energy required for CO2 recovery was in the poly(ionic liquid) when compared to all the ionic liquids and the MEA solution process. The different energy required for all the ionic liquids and the MEA solution process could be reduced by increasing the amount of ionic liquids. A novel non-symmetrical aluminium(III) chloride salen complex [AICI( salenac )OH] was synthesised and investigated in the catalytic cyc1oaddition of CO2 into styrene oxide. The influence of temperature on reactivity and the reaction kinetics using this catalyst was compared with a binary catalyst system. The AICI(salenac)OH showed the better catalytic activity in the synthesis of styrene carbonate at atmospheric CO2 pressure, when compared to a symmetrical aluminium salen complex reported in literature. The cycloaddition reaction was favoured at high temperature, although tetrabutylammonium bromide (Bu4NBr) was used to enhance the catalytic reaction with the AICI(salenac)OH. The styrene carbonate synthesis by a binary catalyst system required a lower activation energy, when compared to the AICI(salenac)OH alone. ii
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.578710  DOI: Not available
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