Asphaltenes correspond to the fraction of oil that is insoluble in heptane but is
soluble in toluene. The aggregates of asphaltene are of interest because they cause serious
problems in the production of oil. Asphaltenes contain fluorescent moieties, and as such
they can be studied by fluorescence techniques.
The first objective of this work was to develop methodologies to study the
fluorescence of asphaltenes, and to investigate the fluorescence of asphaltenes at various
concentrations. Time-resolved fluorescence studies indicate that asphaltenes have
different chromophores with different lifetimes. The average lifetime of the asphaltene
emission decreased when the asphaltene concentration was increased because of
quenching processes occurring within the aggregates. The measurement of lifetimes at
different excitation and emission wavelengths demonstrated that different components of
asphaltene aggregate at different concentrations.
The second objective of this work was to investigate how accessible the
asphaltene aggregate is to small molecules by fluorescence quenching experiments.
Nitromethane was the quencher used in the fluorescence of asphaltenes. The quenching
efficiencies were found to be independent of the concentration of asphaltenes. However,
the quenching efficiencies differed for different chromophores, suggesting a selective quenching for nitromethane of the excited states for the different chromophores of
asphaltenes.
The third objective of this thesis was to investigate the fluorescence of externally
added probes that might be incorporated in asphaltene aggregates through π−π stacking.
Pyrene was chosen as the probe because its fluorescence properties are strongly affected
by its surroundings. The pyrene emission was quenched by nitromethane. The quenching
efficiencies determined for pyrene in the absence or the presence of asphaltene
aggregates were the same. This suggests that pyrene is located in an open environment,
where the asphaltene aggregates do not offer any protection for pyrene from
nitromethane. / Graduate
| Identifer | oai:union.ndltd.org:uvic.ca/oai:dspace.library.uvic.ca:1828/5706 |
| Date | 16 October 2014 |
| Creators | Zhang, Hui Ting |
| Contributors | Bohne, Cornelia |
| Source Sets | University of Victoria |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Rights | Available to the World Wide Web |
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