Date of Award

Fall 12-2011

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry and Biochemistry

Committee Chair

Dr. J. Paige Buchanan

Committee Chair Department

Chemistry and Biochemistry

Committee Member 2

Dr. James Wynne

Committee Member 3

Dr. Douglas Masterson

Committee Member 3 Department

Chemistry and Biochemistry

Committee Member 4

Dr. Wujian Miao

Committee Member 4 Department

Chemistry and Biochemistry

Committee Member 5

Dr. Sarah Morgan

Committee Member 5 Department

Polymers and High Performance Materials

Abstract

Asphaltenes represent a ubiquitous problem in the oil industry due to their adverse effects on recovery, production, and processing equipment. These problems have affected oil companies throughout the world, resulting in significant financial losses. In order to expand the existing body of knowledge related to asphaltenes, we have examined how the presence of naphthenic acids contributes to the particle aggregation and sedimentation behavior of asphaltene suspensions as well as how the physics and chemistry of a substrate affect asphaltene adsorption/deposition.

The flocculation of asphaltenes in the presence of naphthenic acids was investigated using dynamic light scattering (DLS), near-infrared spectroscopy (NIR), and molecular modeling calculations. In these studies the flocculation of asphaltenes was monitored as function of added precipitant to model asphaltene solutions alone and in the presence of select naphthenic acids. A delay in the onset of flocculation was observed in naphthenic acid-containing samples by DLS and NIR, showing good agreement among the two light-scattering techniques. Additionally, molecular modeling calculations supported the experimental results and allowed for the determination of specific structure property relationships among constituents.

A quartz crystal microbalance with dissipation measurements (QCM-D) was implemented in order to probe how the physics and chemistry of a substrate affected the adhesion of asphaltene particles. In this work SiO2-coated QCM-D sensor crystals were chemically modified with different organosilane compounds, and the degree of asphaltene adsorption on these surfaces was examined. The derivatized sensor surfaces were characterized with solvent contact angle measurements and surface energy calculations using well-established methods. Contact angle measurements showed that the derivatized surfaces varied in their degree of hydrophilicity and supported surface functionalization. Additionally, surface energy calculations varied over a wide range of values. The QCM-D experiments revealed that all of the surfaces adsorb asphaltenes roughly to the same extent with the exception of the amine derivatized surface. In the case of the amine surface, a greater asphaltene mass was adsorbed and a distinctly different adsorption profile was observed compared to the other surfaces investigated. It is believed that there is a possible reaction taking place between the primary amine on the sensor surface and an activated carbonyl group on the asphaltene molecule. Dissipation shifts were small throughout all of the QCM-D experiments suggestive of a rigidly attached layer of asphaltenes on the substrate. Maximum rates of asphaltene adsorption were calculated on each surface; however, rates were similar among the surfaces studied with the exception of the carboxylic acid derivatized surface. The carboxylic acid derivatized surface adsorbed asphaltenes at a greater rate which was expected due to the findings from the first phase of this research effort describing the strong interactions between asphaltenes and organic acids. Plots of the adsorbed asphaltene mass versus the

calculated surface energy for each surface by each method were generated; however, the plots did not reveal a correlation between the surface energy and mass of asphaltenes adsorbed.

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