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The Phase Behavior of Asphaltene + Polystyrene + Toluene Mixtures at 293 K Open Access


Other title
asphaltene polystyrene toluene non-adsorbing polymer colloid depletion flocculation acoustic speed
Type of item
Degree grantor
University of Alberta
Author or creator
khammar, Merouane
Supervisor and department
John M. Shaw (Chemical and Materials Engineering)
Examining committee member and department
Hongbo Zeng (Chemical and Materials Engineering)
Jérôme Pauly (Laboratoire des Fluides Complexes et Leurs Reservoirs, Université de Pau, France)
Rick Chalaturnyk (Civil and Environmental Engineering)
Phillip Y. K. Choi (Chemical and Materials Engineering)
John M. Shaw (Chemical and Materials Engineering)
Murray R. Gray (Chemical and Materials Engineering)
Department of Chemical and Materials Engineering

Date accepted
Graduation date
Doctor of Philosophy
Degree level
Polymers of various types are added to crude oils and oil products to prevent wax deposition, break water-in-oil emulsions, reduce drag in pipelines and to stabilize asphaltenes. In mixtures where a polymer does not adsorb on colloids, two stable liquid phases can arise due to depletion flocculation. Asphaltenes in heavy oils and toluene mixtures form sterically stabilized colloidal particles. In this work, the addition of a non-adsorbing polymer (polystyrene) to C5 Maya asphaltene + toluene mixtures was investigated experimentally and theoretically. As concentrated asphaltene + toluene mixtures are opaque to visible light, phase volumes and compositions were detected using ultrasound. The sensors comprised two commercial 64 element phased-array acoustic probes. The operation of the view cell, and kinetic and equilibrium data processing procedures were validated using mixtures of methanol + alkanes. Acoustic speed and attenuation profiles were found to provide independent measures of phase separation. At equilibrium, acoustic speed profiles are uniform in each phase with a step change at the interface. Acoustic wave attenuation profiles exhibit a sharp peak/spike at liquid-liquid interfaces. Mixtures of asphaltenes + polystyrene + toluene are shown to exhibit liquid-liquid phase behavior over broad ranges of composition. This is the first report of liquid-liquid phase behavior for such mixtures. One phase is asphaltene rich and the other phase is polystyrene rich. Liquid-liquid critical points were also identified along the liquid-liquid/liquid phase boundary for mixtures with two mean molar masses of polystyrene. Compositions of co-existing phases were computed using phase volume variations along dilution lines, acoustic speed data and a mass balance model. A parameter was introduced to improve the agreement between calculated and experimental speeds of sound. The results of the model indicate that more than half of the asphaltenes, by volume, participate in the depletion flocculation process. Phase compositions were measured independently using UV-visible spectrophotometry. The nominal size of asphaltene colloidal particles participating in the phase separation mechanism was estimated by comparing calculated phase boundaries with the experimental phase diagram. The estimated size of asphaltene colloidal particles is in agreement with the expected size of asphaltenes in toluene mixtures obtained exogenously.
License granted by Merouane Khammar ( on 2011-04-12T06:19:56Z (GMT): 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 the above terms. The author reserves all other publication and other rights in association with the copyright in the thesis, and except as herein 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.
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