A detailed examination of the solution behaviour and crystallisation kinetics of fatty acid methyl esters (FAME) is presented. The systems studied are: methyl palmitate, methyl stearate and their binary mixtures in dodecane and methyl oleate solvents. Fractionation behaviour in palm methyl ester, soybean methyl ester and rapeseed methyl ester fuel is also studied. Two principal techniques are employed in this work, i.e. turbidometric analysis of solutions during polythermal cycles and the gas chromatography analysis of solution supernatants as a function of temperature. The foundations of these two studied have been laid via the x-ray diffraction (XRD) analysis of the solid-state forms of methyl palmitate and methyl stearate crystallised from solution. No evidence is found to suggest that the methyl stearate and methyl palmitate binary mixtures crystallise from methyl oleate solvent as a solid solution and no shift in the XRD patterns generated, i.e. no transition in solid state form crystallised is observed for the conditions under which solutions are crystallised. It is found that solution behaviour for methyl palmitate, methyl stearate and their binary mixtures in both solvents is in negative deviation to ideality, with the pure solutes being the more deviated in comparison to the binary mixtures. Eutectic points are discovered at a composition of 75 mol% C16:0 in the C16:0 I C18:0 binary mixture crystallisation from both solvents. Metastable zone widths (MSZW) are larger for both solutes in the methyl oleate solvent (6-9.50C) as compared to dodecane (3-6.5oC) and MSZWs are significantly smaller at the 100mI scale, being about half those at the 1ml scale. Nucleation rates for both solutes and their binary mixtures are about 2-13 k gilimin over a 100-250 g/l concentration range in both solvents. From the palm methyl ester and its blends with soy methyl ester and rapeseed methyl ester only C16:0 is found to crystallise at the cloud points. A thermodynamic model for methyl palmitate and methyl stearate solubilities in methyl oleate solvent predicts the fractionation behaviour in the blended fuels satisfactorily but less well in the pure palm methyl ester.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:590479 |
| Date | January 2012 |
| Creators | Hussain, Qassim |
| Publisher | University of Leeds |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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