Scalable and Concise Approaches for the Synthesis of "Archipelago Model" Asphaltene Compounds

• Author / Creator

  Diner, Colin E

• Asphaltenes constitute the most difficult sub-class of bitumen with regards to upgradability. This is due to their complex and variable structure, higher average molecular weight, and inclusion of polar functionalities. These structural traits instigate intermolecular attractions that lead to irreversible aggregation of individual asphaltene molecules and ultimately precipitation from solution. This behavior hampers the ability to efficiently utilize this material and address society’s growing energy needs.

  At the same time, northern Alberta’s Athabasca region has abundant reserves of asphaltene-rich bitumen. There is thus strong interest in developing new technologies for efficient upgrading of this “low quality” crude petroleum. Progress towards this end requires a thorough understanding of asphaltenes at a molecular and supramolecular level. Due to the complex and intractable mixture that comprises asphaltenes, this intimate knowledge has yet to be garnered, despite great effort.

  Traditionally, an analytical approach towards deciphering the “micro-structure” of the asphaltenes has been utilized, with limited results that are difficult or impossible to validate. As of yet, no pure asphaltene molecule has been characterized structurally. A reverse-engineering approach towards accurate modeling of theoretical class members is expected to have great potential in unraveling the mysteries that remain.

  In this dissertation is described the first concise and scalable synthesis of a range of well-defined asphaltene model compounds obtained in high purity. This new class of synthetic compounds falls within the observed structural guidelines determined for natural samples, both in terms of molecular weight and heteroatom content. These model compounds represent the “archipelago-type” architecture, in that they are composed of polycyclic aromatic “islands” tethered together by saturated alkyl chains of various lengths, and further decorated with shorter terminal alkyl groups. A range of authentic functionality has been introduced into these compounds, although there remain many variants as yet unprepared.

  The foundation of our synthetic approach to these molecules is the traceless cross-coupling of tethers and islands, assembling large carbonaceous skeletons in the terminal step of the synthetic sequence. This feature is pivotal in allowing for simple isolations of otherwise difficult-to-purify targets through extraction and fractional crystallization. All of the reported archipelago model compounds and isolated intermediates have been characterized by 1H- and 13C-NMR spectroscopy, HRMS, and EA. The solid-state structure of one model compound has been determined by X-ray crystallography.

• Subjects / Keywords

  • Concise
  • Asphaltenes
  • Scalable
  • Archipelago Model

• Graduation date

  Fall 2015

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3W37M16D

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.