A NUCLEAR MAGNETIC RESONANCE SPECTROSCOPIC INVESTIGATION OF THE MOLECULAR STRUCTURE AND AGGREGATION BEHAVIOR OF ASPHALTENES RUDRAKSHA DUTTA MAJUMDAR B. Tech., West Bengal University of Technology, India, 2010 A Thesis Submitted to the School of Graduate Studies of the University of Lethbridge in Partial Fulfilment of the Requirements for the Degree DOCTOR OF PHILOSOPHY Department of Chemistry and Biochemistry University of Lethbridge LETHBRIDGE, ALBERTA, CANADA © Rudraksha Dutta Majumdar, 2015 A NUCLEAR MAGNETIC RESONANCE SPECTROSCOPIC INVESTIGATION OF THE MOLECULAR STRUCTURE AND AGGREGATION BEHAVIOR OF ASPHALTENES RUDRAKSHA DUTTA MAJUMDAR Date of Defence: December 03, 2015 Dr. Paul Hazendonk Associate Professor Ph.D. Supervisor Dr. Michael Gerken Professor Ph.D. Supervisor Dr. Stacey Wetmore Professor Ph.D. Thesis Examination Committee Member Dr. Peter Dibble Associate Professor Ph.D. Thesis Examination Committee Member Dr. Locke Spencer Assistant Professor Ph.D. Internal Examiner Dr. Gillian Goward Professor Ph.D. External Examiner Dr. Hans-Joachim Wieden Associate Professor Ph.D. Chair, Thesis Examination Committee DEDICATION To my parents, Jaba and Joshomoy Dutta Majumdar for their sacrifices, and to all the enlightened minds that inspired, critiqued and challenged me to think differently on this academic journey. iii ABSTRACT 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. iv ACKNOWLEDGEMENTS This academic endeavour would not have come to fruition without the assistance and kindness of several individuals. I would like to start by expressing my deepest gratitude to my supervisors Dr. Paul Hazendonk and Dr. Michael Gerken, without whose unwavering support none of the work presented herein would have been possible. I would also like to thank my supervisory committee members, Dr. Peter Dibble, Dr. Stacey Wetmore and Dr. Saurya Das, who have been nothing but supportive and insightful. I extend my gratitude to Dr. Gillian Goward of McMaster University and Dr. Locke Spencer for devoting their time to evaluate the thesis. Two individuals without whom this work would have been exponentially more difficult are Tony Montina and Michael “Mike” Opyr. They are responsible for all of the hands-on knowledge and experience I have with the spectrometer. I would also like to acknowledge Dr. Oliver Mullins and Dr. Andrew Pomerantz of Schlumberger-Doll Research, USA for the valuable discussions and insight. I would like to thank my cousin Deep Mazumdar, without whom I would not have started this journey in the first place. We shall soon be neighbors. I would be ungrateful if I did not thank the PubRats, who always made Friday evenings worth looking forward to. Cheers to you people. Lastly, I would like to thank my parents Jaba and Joshomoy Dutta Majumdar, who have toiled every day of their lives to help me get where I am today. I do not express my gratitude often enough, but I am thankful. v TABLE OF CONTENTS TITLE PAGE ........................................................................................................................ i THESIS EXAMINATION COMMITTEE MEMBERS .................................................... ii DEDICATION ................................................................................................................... iii ABSTRACT ........................................................................................................................ iv ACKNOWLEDGEMENTS ................................................................................................. v TABLE OF CONTENTS .................................................................................................... vi LIST OF TABLES ............................................................................................................... x LIST OF FIGURES ............................................................................................................ xi LIST OF ABBREVIATIONS ........................................................................................... xvi 1. ASPHALTENES .............................................................................................................. 1 1.1. Overview ................................................................................................................... 1 1.2. Petroleum and Economics: The Current State of Affairs ......................................... 4 1.3. Asphaltenes: Definition and Properties .................................................................... 5 1.4. Asphaltene Structure and Chemistry......................................................................... 8 1.4.1. Molecular Weight .............................................................................................. 8 1.4.2. Elemental composition ....................................................................................... 9 1.4.3. Molecular structure ............................................................................................ 9 1.4.4. Asphaltene aggregation .................................................................................... 13 1.5. The Use of NMR Spectroscopy for Asphaltene Characterization .......................... 17 1.5.1. Solution-state NMR Spectroscopy ................................................................... 18 1.5.2. Solid-state NMR Spectroscopy ........................................................................ 24 1.6. Thesis objectives ..................................................................................................... 28 2. NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY ...................................... 30 2.1. Overview ................................................................................................................. 30 2.2. NMR Spectroscopy Fundamentals ......................................................................... 31 2.2.1. Nuclear Spin and Magnetism ........................................................................... 31 2.2.2. Signal Generation, Relaxation and the NMR Experiment ............................... 35 2.2.3. Chemical Shielding and Chemical Shift .......................................................... 41 2.2.4. Nuclear Spin Interactions: J- and Dipolar Coupling ........................................ 49 2.2.5. Magic-Angle Spinning ..................................................................................... 53 2.2.6. Decoupling ....................................................................................................... 56 2.2.7. Product Operators ............................................................................................ 58 2.2.8. Coherence Transfer .......................................................................................... 64 2.2.9. Spin Echo ......................................................................................................... 65 2.2.10. INEPT (Insensitive Nuclei Enhanced by Polarization Transfer) ................... 67 2.2.11. Cross Polarization (CP) .................................................................................. 69 2.2.12. Relaxation and Molecular Motion ................................................................. 72 2.2.13. Nuclear Overhauser Effect ............................................................................. 76 2.3. Selected NMR Spectroscopic Experiments ............................................................ 79 2.3.1. One dimensional 1H NMR Spectroscopy ........................................................ 79 2.3.2. One dimensional 13C NMR Spectroscopy ....................................................... 80 2.3.3. 13C NMR with inverse gated proton decoupling .............................................. 82 vi 2.3.4. T1 and T2 Relaxation Experiments ................................................................... 83 2.3.5. Heteronuclear Single Quantum Coherence Experiments................................. 86 2.3.6. 1H Nuclear Overhauser Effect Spectroscopy (NOESY) .................................. 90 2.3.7. 1H-to-13C Cross-Polarization under Magic Angle Spinning (CP-MAS) Experiments ............................................................................................................... 94 2.3.8. CP Dipolar Dephasing ..................................................................................... 99 2.3.9. 1H Dipolar Filter ...........................................................................................