Probing Flocculation of Polyaromatic Compounds and Asphaltene Subfractions Using DLS

  • Author / Creator
    Wang, Xi
  • In this research, flocculation of fractionated asphaltenes was studied using dynamic light scattering (DLS). Three asphaltene fractions were obtained based on its adsorption characteristics onto calcium carbonate. The DLS results showed that the irreversibly-adsorbed asphaltenes (Irr-Ads), containing the highest number of polar groups, was the fraction responsible for the observed flocculation of whole asphaltenes. To better understand the aggregation behavior of asphaltenes, flocculation of three polyaromatic compounds (PAs), N-(1-hexylhepyl)-N’-(5-carboxylicpentyl)-perylene-3, 4, 9, 10-tetracarboxilicbisimide (C5Pe), N-(1-undecyldodecyl)-N’-(5-carboxylicpentyl)-perylene-3,4,9,10-tetracarboxylbisimide (C5PeC11) and N,N’-bis(1-undecyldodecyl)perylene-3,4,9,10-tetracarboxylbisimide (BisAC11) was further studied using DLS. The findings corresponded well with the results of studying nanoaggregation using electron spray ionization mass spectroscopy (ESI-MS). The flocculation of polyaromatic compound was found to be enhanced by increasing heptane content in the solvent. Among the three polyaromatic compounds studied, C5PeC11 showed similar flocculation kinetics to the Irr-Ads asphaltenes. Experiments using mixed PA compounds showed reduced flocculation tendency of C5PeC11 under otherwise identical solution conditions. The presence of polar groups in polyaromatic compounds was shown to be important in accelerating the flocculation of PA compounds beyond nano-scales. The results from molecular dynamics simulation study suggests that π-π stacking between polyaromatic cores, hydrogen bonds from polar groups and tail-tail interactions among aliphatic chains are all important to aggregation of PA (asphaltene) molecules. Taken together, this study provides a scientific basis for future manipulations of polyaromatic compounds aggregation and sheds light on understanding the flocculation onset of asphaltenes in crude oil.

  • Subjects / Keywords
  • Graduation date
    Spring 2017
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • 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.