Phase Diagrams for Asphaltene and Asphaltene-Rich Hydrocarbons + Polystyrene + Toluene mixtures

• Author / Creator

  Chowdhury, Sourav

• Heavy oils are nano-colloids comprising a continuous maltene-rich liquid phase and a nano-dispersed asphaltene-rich phase separable by filtration that are macroscopically homogeneous. The asphaltene-rich phase can aggregate and deposit, causing technological risk and process operation challenges for the hydrocarbon production, transport and refining industries. When non-adsorbing polymers are added to nano-colloids two stable macroscopic fluid phases arise due to depletion flocculation. One phase is rich in polymer (polystyrene in this case) and the other phase is rich in nano-colloid (asphaltenes in this case). In the present study the phase behavior of mixtures comprising chemically separated pentane asphaltenes + toluene + atactic polystyrene (400,000 AMU) is revisited and the phase behavior of Athabasca bitumen (naturally-occurring hydrocarbon resource with 18.6 wt.% pentane asphaltenes) + toluene + atactic polystyrene (400,000 AMU) mixtures is explored. For both mixtures critical points associated with depletion flocculation and depletion re-stabilization are identified on closed loop two-phase to one-phase boundaries. The experimental methods, phase boundaries, tie lines and fluid-fluid critical points are presented and discussed. We show that X-ray transmission is more robust than acoustic transmission for the identification of two-phase to one-phase boundaries and critical points in these mixtures. The outcomes of this work are expected to improve the understanding of asphaltene behaviours in current production, transport, and refining processes, and may lead to the development of new low-environmental impact de-asphalting processes for heavy oils.

• Subjects / Keywords

  • Nanofiltration
  • Asphaltene
  • Phase diagram

• Graduation date

  Fall 2018

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R36970D77

• License

  Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.