A nuclear magnetic resonance spectroscopic investigation of the molecular structure and aggregation behavior of asphaltenes
Dutta Majumdar, Rudraksha
University of Lethbridge. Faculty of Arts and Science
Lethbridge, Alta : University of Lethbridge, Dept. of Chemistry and Biochemistry
The molecular and aggregate structure of asphaltenes derived from oil-sands bitumen, heavy black-oil and coal, and their aggregation behavior, have been studied comprehensively using solution- and solid-state nuclear magnetic resonance (NMR) spectroscopic techniques. It is shown using solution-state relaxation and 2D correlation methods, and cross-polarization-based solid-state techniques that the “island” model is the predominant architecture for asphaltenes derived from Athabasca oil-sands bitumen. Asphaltenes derived from different petroleum and coal sources are compared, and it is shown that alkyl sidechains play a significant role in asphaltene aggregation. The average asphaltene molecule is shown to be larger than previously posited, likely possessing pendant aromatic rings. The very first experimental evidence for alkyl groups intercalated between asphaltene aromatic sheets is presented. Finally, ultrafast magic angle spinning solid-state NMR experiments were used to achieve unprecedented resolution in the solid-state 1H NMR spectrum, allowing for the observation and relaxation measurements of otherwise obscure signals.
Spectroscopy , Nuclear magnetic resonance spectroscopy , Petroleum , Solid-state NMR , Asphaltenes