Type of Document Dissertation Author McKenna, Amy Marilyn Author's Email Address firstname.lastname@example.org URN etd-09162009-104426 Title Detailed Characterization of Heavy Crude Oils and Asphaltenes by Ultrahigh Resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry Degree Doctor of Philosophy Department Chemistry and Biochemistry, Department of Advisory Committee
Advisor Name Title Alan G. Marshall Committee Chair Ken Goldsby Committee Member Michael G. Roper Committee Member Ryan P. Rodgers Committee Member Phillip N. Froelich Outside Committee Member Keywords
- Atmospheric Pressure Photoionization
- Heavy Crude
- FT-ICR MS
Date of Defense 2009-08-21 Availability unrestricted AbstractEventually, the world will deplete the global oil supply and a new form of energy will supplant fossil fuels as the main global energy source. However, technological advances are still decades away from finding a unified solution to meet the energy needs of the global community. Wind and solar energy can be harvested, but only provide a fraction of the required energy. In the meantime, heavy conventional and unconventional crude oil production has increased due to the depletion of low viscosity, sweet crude.
Oil companies sell molecules. Comprehensive compositional characterization of refinery feeds allows for production and refinery strategy development. Oil companies convert high-boiling fractions to increase product yields for valuable, low-boiling fractions. Development of chemical processes to maximize profits requires an exhaustive characterization of each molecule in heavy crude fractions. Bulk property measurements combined with analytical techniques are limited in their ability to separate and characterize each of the tens of thousands of compounds in a single crude oil. The use of mass spectrometry has facilitated the characterization of low-boiling, light crude oils; however, more complex, heavy feeds require extensive separation techniques to produce meaningful compositional information. Ultrahigh resolution FT-ICR mass spectrometry provides the most detailed, comprehensive examination of high-boiling fractions of crude oil.
Chapter 1 provides an introduction to heavy crude oil and bitumen processing and refining. In Chapter 2, a brief introduction to FT-ICR principles and the figures of merit which make it indispensable for complex crude oil mixtures.
Chapter 3 establishes the correlation of atmospheric pressure photoionization (APPI) nebulization temperature with boiling point for an Athabasca bitumen HVGO distillation series. Here, we establish optimal temperatures which are used for the following chapters to ensure complete desorption/ionization while assuring thermal reactions do not occur in the ionization process which would affect subsequent data interpretation.
Chapter 4 begins a four part examination of heavy oil composition and investigates the relationship between molecular weight, structure and boiling point of nonpolar and polar species boiling between 427-538 ¢ªC. Extensive characterization of a heavy vacuum gas oil (HVGO) distillation series provides the first comprehensive test of the Boduszynski model of heavy oil composition. Both electrospray ionization (ESI) and APPI provide insight into the evolution of polar and nonpolar species and show the continuity of crude oil composition as boiling point increases.
In Chapter 5, part II extends the crude oil continuum to the limits of distillation through detailed examination of a Middle Eastern heavy crude distillation series. Extension of the Boduszynski model transitions into a detailed examination of the composition of nondistillable residues.
Chapter 6 characterizes asphaltenes, a solubility fraction of crude oil known to be high-boiling, highly polar and problematic for production, transport and refining of crude oil through deposition, catalyst fouling, and viscosity increases, to name a few. Part III introduces a new fraction of asphaltenes we deem ¡°distillable asphaltenes¡±. Here, we further prove the Boduszynski model through the discovery of asphaltene compounds which boil much lower than previously thought.
Chapter 7 defines asphaltene compositional space in conjunction with their counterpart fraction, maltenes. Asphaltenes and maltenes are separated by their solution-phase behavior through solubility differences in paraffinic solvents (ie, heptane or pentane). However, for twenty years, asphaltene molecular weight has been the subject of a heated debate between those who think they are high molecular weight (<10 kDa) and those who think they are relatively low in molecular weight (> 2 kDa). Mass spectrometry is used to show that asphaltenes are not abnormally high in molecular weight and in fact share carbon number space with maltenes. Compositional differences between asphaltene and maltene species show that asphaltenes are shifted to higher DBE values at the same carbon number than maltenes. Results are combined with reported results in the literature to provide a unified theory of asphaltene composition.
Chapter 8 investigates the phenomena of asphaltene self-association (aggregation) to form stable aggregate structures through noncovalent interactions. Here, we employ time-of-flight mass spectrometry, which allows for much wider molecular weight distributions in a single mass spectrum. We are able to identify and show that asphaltenes are aggregated at concentration levels above those routinely used for mass spectral analysis through a bimodal distribution for the monomer and aggregate at roughly eight times the monomer molecular weight. Solution-phase aggregation of asphaltenes is also examined through high resolution analysis of a mixture of 50/50 asphaltene/maltene by weight to explore the composition of asphaltenes in a mixed matrix.
Chapter 9 identifies and characterizes metal-containing petroporphyrins in raw asphaltene and whole crude oil for the first time by FT-ICR MS. Petroporphyrins are important for removal prior to refining because they are highly corrosive and are known to deactivate catalysts used in conversion processes. Porphyrins have been extensively characterized with other techniques, but tedious separation and isolation is required. Here, different structural classes of vanadyl porphyrins are characterized by APPI FT-ICR MS without prior separation or isolation.
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