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flocculation, polyaromatic compounds, DLS, asphaltene

Wang, Xi

Supervisor and department: Xu, Zhenghe Chemical and Material Engineering

Examining committee member and department: Liu, Qingxia Chemical and Material Engineering Chung, Hyun-Joong Chemical and Material Engineering Zhang, Hao Chemical and Material Engineering

Department: Department of Chemical and Materials Engineering

Specialization: Chemical Engineering

Date accepted: 2016-12-23T12:53:04Z

Graduation date: 2017-06:Spring 2017

Degree: Master of Science

Degree level: Master's

Abstract: 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’-bis1-undecyldodecylperylene-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.

Language: English

DOI: doi:10.7939-R31C1TT3G

Rights: This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for the purpose of private, scholarly or scientific research. 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.





Author: Wang, Xi

Source: https://era.library.ualberta.ca/


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Probing Flocculation of Polyaromatic Compounds and Asphaltene Subfractions Using DLS by Xi Wang A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Chemical Engineering Department of Chemical and Materials Engineering University of Alberta ©Xi Wang, 2016 Abstract 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-(1hexylhepyl)-N’-(5-carboxylicpentyl)-perylene-3, 4, 9, 10-tetracarboxilicbisimide (C5Pe), N-(1undecyldodecyl)-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 IrrAds 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 ch...





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