The analysis of salt resistant surfactants used in enhanced oil recovery

Commercial nonylphenol ethoxysulphonate (NPEOS), octylphenol ethoxysulphonate (OPEOS) surfactant formulations and mixtures of alkyl aryl sulphonate and NPEOS surfactant formulations, are used for enhanced oil recovery (EOR). The surfactants have been analysed by liquid chromatography (LC), liquid chromatography-mass spectrometry (LC-MS) and matrix assisted laser desorption ionization mass spectrometry. Mixedmode C1 8/SAX and C8/SAX columns were used for both liquid chromatography and liquid chromatography-mass spectrometry analyses of NPEOS and OPEOS. NPEOS and alkyl aryl sulphonate surfactant mixtures were separated using a mixed-mode C4/SAX column.. Matrix assisted laser desorption ionization mass spectrometry (MALDI-MS) spectra were obtained using either alpha-cyano-4-hydroxycinnamic acid or 2,5-dihydroxybenzoic acid as matrix with the addition of lithium chloride to simplify the mass spectra obtained. Data obtained from each method indicate that the NPEOS formulation has an ethoxymer chain length ranging from 2-13 units with average of 6.26. This is in broad agreement with earlier studies, although the range was reported as 2-15. However, the data obtained suggest that the OPEOS formulation has an ethoxymer chain length ranging from 1-8 ethoxymer units with an average chain length of 3.67. This is in contrast to earlier studies carried out by LC only, which suggested that the chain length ranged from 2 to 6 ethoxymer units with an average of 3.6. A method for the extraction of NPEOS and OPEOS from sea-water and reagent water, and alkyl aryl sulphonate from sea-water only, using graphitised carbon black (GCB) solid phase extraction (SPE) cartridges has also been developed.In the last section of this thesis the chemical oxidation of NPEOS used Fenton's reagent and biological oxidation of NPEOS using a microorganism (Paracoccus halodenitrificans) is reported. The intermediate products formed in the chemical oxidation have been identified and characterized by LC, LC-ES-MS and MALDI/MS techniques. The major products formed are dicarboxylic acids and single carboxylic acids. The aerobic biodegradation of NPEOS was carried out over five days. Theoxygen uptake was measured each day. The biodegradation intermediate products were analysed by LC and data indicate that the same products were formed as those from the chemical oxidation of NPEOS.