@article{singh_mclean_kilpatrick_1999, title={Fused ring aromatic solvency in destabilizing water-in-asphaltene-heptane-toluene emulsions}, volume={20}, ISSN={["1532-2351"]}, DOI={10.1080/01932699908943792}, abstractNote={Abstract The role of asphaltenes in stabilizing water-in-crude oil emulsions is extremely well established. The mechanism appears to be one in which planar, disk-like asphaltene molecules aggregate through lateral intermolecular forces to form primary aggregates or micelles which are interfacially active. These aggregates — upon adsorbing at the oil-water interface — crosslink through physical interactions to form a viscoelastic network, which has been characterized by some as a “skin” or a “plastic film”. The strength of this film, as gauged by shear and elastic moduli, seems to correlate well with water-in-oil emulsion stability. What is still relatively unknown is the role of chemistry in governing the strength of these lateral inter-asphaltene interactions. The candidate interactions include π-bonding between the delocalized electrons in the fused aromatic ring core, H-bonding between proton donors and acceptors imbedded in the asphaltenic cores, and metal-electron interactions between, for example, h...}, number={1-2}, journal={JOURNAL OF DISPERSION SCIENCE AND TECHNOLOGY}, author={Singh, S and McLean, JD and Kilpatrick, PK}, year={1999}, pages={279–293} }
 @article{mclean_kilpatrick_1997, title={Comparison of precipitation and extrography in the fractionation of crude oil residua}, volume={11}, ISSN={["0887-0624"]}, DOI={10.1021/ef9601125}, abstractNote={Four different crude oilsArab Heavy (AH), Arab Berri (AB), Alaskan North Slope (ANS), and San Joaquin Valley (SJV)were characterized by separating the crudes into compound classes by two different fractionation methodsextrography (ext) and asphaltene precipitation followed by extrographic isolation of the resins (ppt + ext). The fractions derived from these two methods of separation were characterized and compared in order to determine the most complete and discriminating compositional analysis for subsequent use in studies concerning the stability of emulsions or sludges which are produced by these crudes in refinery processing. The resin and asphaltene fractions are of primary interest due to their polar, surface-active nature, the central role these fractions play in stabilizing emulsions and sludges, and their resulting influence on crude processability. Preparatory-scale separations were developed and utilized to provide sufficient amounts of the polar fractions of these crudes for further studies. T...}, number={3}, journal={ENERGY & FUELS}, author={McLean, JD and Kilpatrick, PK}, year={1997}, pages={570–585} }
 @article{mclean_kilpatrick_1997, title={Effects of asphaltene aggregation in model heptane-toluene mixtures on stability of water-in-oil emulsions}, volume={196}, ISSN={["0021-9797"]}, DOI={10.1006/jcis.1997.5177}, abstractNote={As part of an ongoing investigation into the stability of water-in-crude oil emulsions, model oils have been utilized to further probe the effects of crude solvency as well as specific resin-asphaltene interactions on emulsion stability. These model oils were constructed by dissolving varying amounts of resins and/or asphaltenes in a mixture of heptane and toluene. The resins and asphaltenes used in this study were isolated from four different crude types-Arab Berri (AB), Arab Heavy (AH), Alaska North Slope (ANS), and San Joaquin Valley (SJV)-and characterized in a previous study using heptane precipitation of the asphaltenes followed by an extrographic separation of the resins from silica gel. Asphaltenes dissolved in heptol at concentrations of just 0.5% were shown to generate emulsions which were even more stable than those generated from their respective whole crude oils. Some types of resins (e.g., from AH and SJV) also demonstrated an ability to stabilize emulsions although these resin-stabilized emulsions were considerably less stable than those prepared with asphaltenes. The primary factors governing the stability of these model emulsions were the aromaticity of the crude medium (as controlled by the heptane:toluene ratio), the concentration of asphaltenes, and the availability of solvating resins in the oil (i.e., the resin/asphaltene or R/A ratio). The model emulsions were the most stable when the crude medium was 30-40% toluene and in many cases at small R/A ratios (i.e., R/A </=1). This strongly supports the theory that asphaltenes are the most effective in stabilizing emulsions when they are near the point of incipient precipitation. The types of resins and asphaltenes used to construct these model oils also played a role in determining the resultant emulsion stability which indicates the importance of specific resin-asphaltene interactions. The interfacially active components that stabilized these model systems were the most polar and/or condensed portions of the resin and asphaltene fractions as determined by elemental and neutron activation analyses. All of these results point to the significance of the solubility state of the asphaltenes in determining the emulsifying potential of these crude oils. Copyright 1997 Academic Press. Copyright 1997Academic Press}, number={1}, journal={JOURNAL OF COLLOID AND INTERFACE SCIENCE}, author={McLean, JD and Kilpatrick, PK}, year={1997}, month={Dec}, pages={23–34} }
 @article{mclean_kilpatrick_1997, title={Effects of asphaltene solvency on stability of water-in-crude-oil emulsions}, volume={189}, ISSN={["0021-9797"]}, DOI={10.1006/jcis.1997.4807}, abstractNote={Abstract The formation of stable and persistent emulsions and foams in the production and refining of crude petroleum is a challenge which has defied broad and generic resolution for several decades. Rational and systematic approaches to demulsification have been slow to develop due to a lack of fundamental understanding of the molecular origins of emulsion stabilization and the full range of factors which govern emulsion stability. Several studies have shown the importance of resins and asphaltenes, which have the ability to organize and form rigid films at the oil/water interface. We have developed a molecular model in which we propose that the integrity of these films and thus their ability to stabilize water-in-crude-oil emulsions are sensitive to a variety of crude solvency parameters, such as aromaticity, resin-to-asphaltene ratio, and polar functional group concentration. This model was tested by correlating the stability of emulsions formed from a variety of crude oils—Arab Berri (Extra Light), Arab Heavy, Alaska North Slope, and San Joaquin Valley—in which the resin and asphaltene contents vary, as well as their specific characteristics. The results of the elemental and functional group characterization of these crudes and their fractions and the techniques utilized to obtain them were presented previously. Detailed quantitative protocols for gauging relative emulsion stability have been developed to further evaluate the proposed model by blending solvents of varying aromaticity and by doping isolated resins from different crudes into solvent-modified crudes. Dramatic destabilization of emulsions was accomplished by modifying the crude solvency in either fashion. Simple physical and chemical techniques for minimizing emulsion formation such as basic crude blending and solvent-recycle schemes will also be discussed.}, number={2}, journal={JOURNAL OF COLLOID AND INTERFACE SCIENCE}, author={McLean, JD and Kilpatrick, PK}, year={1997}, month={May}, pages={242–253} }