Microscopic Studies of Surfactant Vesicles Formed During Tar Sand

Chapter 21

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Microscopic Studies of Surfactant Vesicles Formed During Tar Sand Recovery Mohammad-Ali Sadeghi, Kazem M . Sadeghi, Dawood Momeni, and Teh Fu Yen School of Engineering, University of Southern California, Los Angeles, CA 90089-0231

By applying ultrasonic energy and using an alkaline solution, self-propagating surfactants are formed. The principle of membrane-mimetic chemistry via the process mechanism is being explored in this work by the thorough examination of the photomicrographs. Giant-sized multilamellar surfactant vesicles are analyzed under both transmittance and reflectance light during their initial formation and, after a few hours, four months, and three years following the completion of the process. From these studies, the optimum time period needed for the vesicles to stabilize is determined. The vesicles are proven to be very stable under the slow reaction condition of six-hour process time. With free radical initiator added (e.g., H O ), the reaction takes minutes to complete. Based on the surfactant vesicles characterization derivedfromcurrent investigations, it is suggested that these surfactants could retain their effectiveness necessary for bitumen recovery in the reservoir environment for a number of years. 2

2

Tar sands, also called bituminous sands or oil sands, are essentially siliceous materials such as sands, sandstones or diatomaceous earth deposits impregnated with 5 to 20 percent by weight of a dense, viscous, low gravity bitumen. Deposits of tar sands exist and are widely distributed throughout the world. Wen et al. (I) pointed out that bitumens, increasing in the order of the size and complexities, consist of the followingfractions:(1) gas oil, (2) resin, (3) asphaltene, (4) carbene, and (5) carboid. The chemical and physical properties of tar sands depend significandy on the relative amounts of eachfractionand their properties. The values of molecular weight, number of condensed aromatic rings, number of heteroatoms (N, O, S) and concentration of 0097-6156/89/0396-^)391$06.00A) o 1989 American Chemical Society In Oil-Field Chemistry; Borchardt, John K., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989.

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metals (V, Ni, Tl, etc.) all generally increasefromthe gas oil fraction to the preasphaltenefraction(carbene and carboid). Generally, there are three types of hydrocarbons present in bitumens; paraffinic, naphthenic, and aromatic, although many of the molecules are combinations of the three types, especially the heavier fractions. Self-generated surfactants (producedfromfossil fuels by a chem ical/physical process) or natural surfactants (exiting in fossil fuels) are derivedfromthe inherent organic acids and replaceable acidic protons which are present in crude oils or bitumens (e.g., mercaptans). Yen and Farmanian (2) isolated native petroleumfractionsthat form sur factants and contain hydrogen displacable components including one, two, three, or four of the following types: R-SH R-NH(Ri) R-OH R-COOH

in which R is a hydrocarbon of 3 to 20 carbon atoms, R\ is hydro gen or a hydrocarbon of 3 to 20 carbon atoms, and R and R\ are either separate or cyclically combined. These acids, when coining into contact with alkaline solutions, yield in-situ surface active materials or self-generated surfactants of various forms of liquid crystals (e.g., giant micelles, large vesicles, etc.). These self-generated surfactants reduce the interfacial tension between the crude oil hydrocarbon and water. In the tar sand production processes in operation in Alberta, Canada, caustic additives (e.g., NaOH) are used to improve recovery rates by about 15%. Bowman (3) isolated some of the dissolved or ganics by foamfractionationtechniques and showed that the materials were surfactants. A similar discovery was found by Ali (4), where a tentative mechanism was given as the following: R-S-R'

+0

2

>R-SO - R' RSO H + R'COOH x

(x = 2 or 3; sulphenic or sulphonic acids). He concludedfromin frared studies that the two functional groups of carboxylic acids and sulphonic acids were on the same molecule, in other words, that the parent sulphide was a cyclic one. The study on the reactions initi ated by ultrasonic energy in the U.S.A. dates back to 1927, which is about the same period for the research on the reaction initiated by

In Oil-Field Chemistry; Borchardt, John K., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989.


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ionizing radiation (5). The mechanisms, responsible for the observed increases in rates in transport and unit operation processes utilizing ultrasonic energy, can be divided into two categories; (1) First-order effects offluidparticles (acceleration, displacement, and velocity) and (2) Second-order phenomena (cavitation, radiation pressure, acoustic streaming, and interfacial instabilities). Mostly, it is one or more of the second-order effects which are responsible for the enhancements in the transport process (6). The use of ultrasonic energy in conjunction with self-generated surfactants to recover bitumen from tar sand is a new extraction technique having a 95% recovery and reaction times that are in minutes (7,8). Chan et al. (9,10) proposed a simple equilib rium chemical model for the surface reaction at heavy crude oil-caustic interfaces. Each acid species dissociates at certain pH value, referred to as the onset pH or pK value, and yields the surface active anion. The dissociation constant of each species depends on its molecular size and structure. For crude oil, being such a complex mixture of organic acids, the pK values rangefrom8 to 11 (11). Some other components in crude oil besides fatty acids have been reported as be ing interfacially active (12,13). It was reported that compounds of zinc, copper, nickel, titanium, calcium, and magnesium were found to be adsorbed selectively to crude oil-water interfaces. All these metals occur in petroleum as porphyrin-metal chelates, or other types of com plexes or even possibily form non-nitrogen binding complexes. The interfacialfilmswere thought to consist of waxes and resins with stabi lizing porphyrin-metal complexes,freeporphyrins, porphyrin oxidation products and protein-metal salts or complexes. The concept of differing pK values for the different acidic species has been used to suggest a method of enhancement for genera tion of self-propagating surfactants formed during the bitumen extrac tion process (Yen, T.F., USC, Unpublished data). By the application of ultrasonic energy and using an alkaline solution, self-propagating sur factant vesicles are formedfromthe natural surfactant vesicles which have onion-like multicompartment structures. Prolonged ultrasonication of these results in the formation of submicroscopic spheroidal vesicles consisting usually of a fairly uniformed single-compartment bilayer surfactant vesicle surrounding a solvent core (14). The reaction can be reversible. Many unilamellar vesicles can coalesce together and form a giant multilamellar vesicle in which the liquid-crystal feature can be observed in microscopic range using a polarized light source and analyzer. To verify the existence of self-generated surfactants during tar sand recovery process and to analyze their structural behavior, the vesicles are studied in this work under transmittance and reflectance light of the microscope. The principles of membranemimetic chem istry are employed to describe the process phenomena. The vesicles' stability for a prolonged period of time is carefully studied and the duration for these surfactants which can withstand the severity of the a

a

a


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reservoir environmental conditions to effectively enhance the bitumen recovery efficiencyfromtar sand deposits is evaluated. EXPERIMENTAL Tar sand samples minedfromAthabasca, in Alberta, Canada, were High Grade Athabasca Tar Sand, Sample No. 1981HG. The bitumen present in the tar sand was 14.5% by weight as determined by Soxhlet extraction (15). A quantity of 100 grams of tar sands was added to a 800 ml of alkaline solution (20:1 by volume distilled water to sodium silicate) and sonicated for several hours until all the bitumen had dissipated in the solution (sand was bitumen-free). The sodium sil icate reagent (Na SiOs) was BJ-120 (wt. ratio Si0 /Na 0 = 1.80) from the PQ Corporation, Huntington Beach, CA. A 10-gallon transducerized tank (Branson Model ATH610-6) and a companion generator (Branson Model EMA 0-6) having six piezo- electric transducers with a 40 kHzfrequencywas used. We have reported the detailed exper imental procedures in previous publications (7,8,15,16). As reported before (8), the reaction takes minutes to recover bitumen with the aid of radicals (e.g., hydrogen peroxide, benzoyl peroxide). The slow re action kinetics (no radicals added) were used to isolate the micelles formed during the process, for analysis under the microscope. The surfactants formed in the tar sand recovery were exam ined using light microscopic techniques. A representative sample was pipeted during sonication and immediately taken for observation under a Leitz SM-Lux-Pol Cross Polarizing Microscope. One drop of each sample to be examined was placed over a clean glass slide and re strained with a cover lid. Photomicrographs were then taken (equipped with a high speed camera and colorfilmusing WILD MPS 15 Semiphotomat) of both reflection polarized light and transmittance of the inci dent light upon the sample. Air tight amber vials were used to store the processed solution for the given durations of twelve hours, four months and three years, before examining the surfactants under the microscope. 2

2

2

RESULTS AND DISCUSSION The heavy-end portions (usually called heavyfractions)of bitumen (e.g. asphaltenes, preasphaltenes) can exist both in a random oriented particle aggregate form or in an ordered micelle form, peptized with resin molecules (16,17). In their natural state, asphaltenes exists in an oil-external (Winsor's terminology) or reversed micelle. The polar groups are oriented toward the center, which can be water, silica (or clay), or metals (V, Ni, Fe, etc.). The driving force of the polar groups



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assembled toward the center originates from either hydrogen-bonding, or charge transfer, or even acid-base salt formation. In crude oil, asphaltene micelles are present as a discrete or colloidally dispersed particles in the oily phase. As the various inter mediate and low boiling fractions are removed during the distilling or evaporation process, the particles of asphaltene micelles are massed to gether to form the larger colloidal sizes (Yen, T. F., "Asphaltic Materi als," Encyclopedia of Polymer Science & Engineering, 2nd Ed., John Wiley, in press). The so-called precipitation or aggregation processes are colloidal in nature (Figure 1). Single sheet, usually the pi-system with saturated substitutes, is associated into stacks or piles of 4-5 lay ers. These "stacks" are commonly referred to as "asphaltenes", which are precursors of micelles (18,19) (either reverse, random-oriented or normal) and the supermicelle. The accompanied transformation of liq uid crystal-gel stage or thefloestage is widely observed in industrial practices. Actually, investigators have isolated supermicelles, particles, floes, etc. and performed many experimental determinations, including molecular weights which rangefroma few thousand up to hundreds of millions. They all attribute this discrepancy to "asphaltene", which may be misleading for other investigators. One knows for certain that the single sheet of asphaltene is under 1000 in molecular weight. Often people believe this is the controversy of Yen's model (20) of asphal tene, yet clearly allfindings,including the most recent ones (21,22), can always be interpreted by that simple model. It is essential to state that the heavyfractionssuch as asphaltene and preasphaltene do contain large numbers of polar molecules (23,24). These polar molecules behave exactly as surfactants or amphiphiles (asphaltene usually contains a long-chain substituent (25)). We again have to emphasize that it is almost not possible to create a colloidal mi cellefrompure hydrocarbon and water without any surfactant. Hence, we conclude to say that asphaltene or asphaltene-like molecules (asphaltics) will participate in a manner according to membrane-mimetic chemistry. Surfactant molecules can be considered as building blocks for certain forms of geometry in colloidal chemistry. Various forms of as sociation molecules can be obtained as the concentration of surfactant in water is increased and/or physicochemical conditions are changed (e.g. CMC, Craft-point, etc.). Figure 2 schematically shows the most likely structural configurations and assemblages of surfactants associa tion in an aqueous system (26). Upon addition of oil and a short-chain alcohol, for example, one can convert the oil-in-water micelles into water-in-oil microemulsions. It is therefore possible to induce a tran sitionfromone structure to another by changing the physicochemical conditions such as temperature, pH and addition of mono or di-valent cations to the surfactant solution. It should be also noted that the sur-


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Asphaltene or Preasphaltene Monomer Units (15-20A) Via Hydrogen Bonding S 7r-7r Bonding


Micelle (22-38A) Rearangement by Amphiphiles

Reversed Micelle

Agglomerate

Hartley Micelle

Peptization by Resins

— Supermicelle (80-100A)

^

Via London Van der Woals Attraction \ Bigger Supermicelle j or Roc (>220X)

Precipitation

PRECIPITATES-K^^ooo^ Figure 1. Asphaltic substances in different stages of a process. The size and weight depend on the environment [modifiedfromRef. 27 and others].


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MilDownloaded by UNIV OF CALIFORNIA SAN DIEGO on January 4, 2016 | http://pubs.acs.org Publication Date: July 10, 1989 | doi: 10.1021/bk-1989-0396.ch021

—

—

monolayer

—

water

spherical micelle

rod-like micelle

black lipid membrane

>watero— reversed micelle

surfactant crystal

397

w/o microemulsion

laminar surfactant • rich phase

o/w microemulsion

large disk-shaped micelle

large rod micelle

vesicle multicompartment vesicle

Figure 2. Some organized structures of surfactants in different media and the effect of sonication to vesicles [modified from Ref. 26 and others].



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factant may skip several phase transitions depending upon its structure and the physicochemical conditions. In an alkaline environment (pH greater than 10), for a membranemimetic system, the interaction of cations (e.g., sodium, potassium) with the peptized resin molecules acts in a membrane mimetic fashion. The cation reacts with the acid-bearing functional group to develop a host-guest cavity in a cylindrical shape. The counter anion (e.g., hydroxide, silicate) is activated and dissolves in the oil phase. In this manner, the resin molecule containing the heterocycle center is dissociated and any ionizable proton such as in -COOH, -SH, or -NH is replaced with the cation. The self-generated surfactant molecules are produced. When this self-generated surfactant migrates into the naturally reversed micelles (oil external-water internal) of asphaltene, it disrupts the polar structure to form a Hartley micelle (polar-external) as shown in Figure 3. This is termed as the "micellar inversion process." The counter anions emulsify the oil and the micellar structure becomes a microemulsion stabilized by the self-generated surfactant molecules (2,15). In the micellar inversion process, the heavyfractions(as phaltenes and preasphaltenes) are separatedfromthe bitumen. This separation results, as the micelles containing the less polar or lighter hydrocarbon components and the individual molecules breaking away from the micelle, moving to the surface of the aqueous phase and coalescing to form an oil layer. After the separation of lighter compo nents, the higher polar molecules form asphaltenes and preasphaltenes micelles strongly reassociated and complexed with metals to form colloidal-sizefloesand precipitates. As Briggs et al. (27) indicated that the preasphaltenefractioncontains an aliphatic to aromatic hydro gen ratio of 3.6, and the presence of alkyl side chains and the larger molecules by weight would attribute to the large size of colloidal par ticles. These particles are formed by inter-molecular association of 3 to 5 polyaromatic molecules (single sheet) of asphaltene and/or pre asphaltene. Most of these colloidal particles are spherical with diame ters in the range of 22-38 angstroms. The ultrasonic vibration energy effect is expected to accelerate the aggregation of these colloidal par ticles through the orthokineticflocculationmechanism. Four of the 22-38 angstroms particles could agglomerate to form a supermicelle or floe with a diameter in excess of 220 angstroms (see Figure 1). Ac cording to many indications, such as x-ray small-angle scattering data (27-29), supermicelle structures with dimensions in excess of 1000 angstroms would precipitatefromthe solution. The purpose of employing various light incidents when using a microscope was to distinguish between different crystals such as min eral crystals (e.g., clays, silicons, NaOH, etc.)fromsurfactant crystals (30-33). It was found that under transmittant light only bituminous hydrocarbons were non-transparent (absorb light) and appeared either



21. SADEGHI ETAL.

o

Surfactant Vesiclesfrom Tar Sand Recovery

P o l a r Groups Aromatic Sheets Saturated Chain or Rings

R S A II

399

Resin Surfactant Asphaltene Hartley Micelle

Figure 3. Dynamic equilibrium of asphaltene micelle inversion process.



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black, orange and/or yellow in photomicrographs. This is the stage of reaction in which the removal of hydrocarbon contaminants is sus pected to take place. As shown in Figures 4a (transmittance) and 4b (reflectance), asphaltic micelles (isotropic black circles) are going through the micellar inversion process (34). At the completion of above reaction (after the 6th hour of sonication) another batch of solution was withdrawn for observation. Figure 4c shows the emulsions that have formed during the reaction. These emulsions were all optically active under polarized light (reflectant) as shown in Figure 4d. This was interpreted as a sign for surfactant activity. Also there were no asphaltic micelles observed in the solu tion, which meant total removal of contaminants had taken place and the contaminants had precipitated as solid asphaltic agglomerates. The emulsions formed during the reaction started to coalesce a few minutes after the processing had stopped (Figures 5a and 5b). At the time of emulsion coalescence, many surfactant molecules rearranged in an or derly fashion and formed a thick layer surrounding some oil emulsions (Figures 5c and 5d). The trapped oil emulsions within the surfactant layer continuously burst and their surfactant molecules moved outwards adding another surfactant layer to the outer boundary. This is the sus pected mechanistic sequence that forms the large multi-compartment surfactant vesicles from single-compartment vesicles during the sonication process. The optical activity of these layers shows the true nature of the surfactant molecules being highly organized. These membrane-mimetic agents are also osmotically active as shown in Figure 6 (4 months later). Notice the centers of the vesicles are completely covered with the upgraded bitumen without any air or water gaps present as compared to Figures 5c and 5d. Also, these vesicles are quite stable even after three years of storage in an air tight amber vial (Figures 7a and 7b). Amber vials were used to avoid any photolysis of the samples which might initiate unsuspected radical reactions. In order to determine whether these surfactant vesicles were of polymerized vesicle forms, a 25% V/V ethanol (standard grade) was added to the three year old sample solution. Alcohols are known (34) to destroy surfactant vesicles derivedfromnatural phospholipids, how ever, synthetically prepared polymerized vesicles are stable in as much as 25% (V/V) alcohol addition. Photomicrographs shown in Figures 7c and 7d indicate that these vesicles partially retain their stability (being mesomorphic) and therefore are suspected to be polymerized surfactants. Whether surfactant molecules of these vesicles are single or multipla bonds in tail, or in head groups remains to be seen. As indicated by Puig et al. (35), surfactant retention and atten dant pressure buildup in the rock can be greatly reduced if the surfac tant dispersion is converted into the liquid crystalline state. Unilameller vesicles are preferred in thefieldwork rather than the multilamellar



401


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Figure 4. Bitumen removal during 3rd/4th hour of the processing [(a) transmittance and (b) reflectance]. Emulsification phenomena af ter completion (6th hour) of the processing [(c) transmittance and (d) reflectance].


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Figure 5. Coalescence phenomena a few hours after completion of the processing [(a) transmittance and (b) reflectance]. Multilamellar surfac tant vesicle development phenomena twelve hours after the completion of the processing [(c) transmittance and (d) reflectance].



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Figure 6. Multilamellar surfactant vesicles four months following the processing [(a) transmittance and (b) reflectance].


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Figure 7. Multilamellar surfactant vesicle three years following the processing [(a) transmittance and (b) reflectance]. Partial disruption of vesicle in 7a and 7b, upon addition of 25% V/V of ethanol [(c) transmittance and (d) reflectance].


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vesicles. Other than the use of sonication, different chemical additives can be equally efficient in the application of vesicles as surfactant de livery agents for enhanced oil recovery or decontamination in soil. CONCLUSION Benchmark studies demonstrated that the application of ultrasonic en ergy in an alkaline solution media (i.e. pH > 10) will induce generation of self-propagating surfactants which could effectively extract bitumen from tar sand deposits. The photomicrographs taken by the applica tion of both the transmittance and reflection of polarized light were carefully analyzed and it was concluded that the surfactant vesicles generated during and after the process completion were quite stable even after three years of storage. This indicates that these surfactant vesicles were polymerized during the processing due to the presence offreeradicals, whether generated by sonication or added as initiators (7,8). The membrane-mimetic chemistry (34) concepts were applied to thoroughly examine the reaction pathways of the process by the mi croscopic studies. The overall studies did indicate clearly that the de velopment of such a process in a tar sand reservoir environment could similarly lead to generation of multiple-layered or multi-compartment surfactant vesicles and subsequently to the ultimate in-situ bitumen re covery. In a similar manner, emulsification, transportation, upgrading, production, recovery, etc., of tar sand and related heavy oil industries can be benefited. ACKNOWLEDGMENTS The authors thank Energy and Environment Research Laboratories, Inc. for partialfinancialsupport. We want to acknowledge Dr. JihFen Kuo of Groundwater Technology, Inc. and Eh*. John G. Reynolds of Lawrence Livermore National Lab for technical discussions. We also thank Dr. H.L. Wong and Mr. Leon Lemons for the preparation of this manuscript. LITERATURE CITED

1. Wen, C. S.; Chilingarian, G. V.; Yen, T. F. "Properties and Structure of Bitumens," Bitumens, Asphalts, and Tar Sands; Chilingarian, G. V.; Yen, T. F., Eds.; Elsevier Publishing Company: New York, 1978, 7, p 155. 2. Yen, T. F.; Farmanian, P. A. "Native Petroleum Surfactants," U.S. Patent 4 411 816, 1983.



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3. Bowman, C. W. "Molecular and Interfacial Properties of Athabasca Tar Sands," Proceedings of the Seventh World Petroleum Congress; Elsevier Publishing Company: New York, 1967, 3, p 583. 4. Ali, L. H. "Surface-Active Agents in the Aqueous Phase of the HotWater Flotation Process for Oil Sands," Fuel, 1978, 57, 357. 5. Chendke, P. K.; Fogler, H . S. "Second-Order Sonochemical Phe nomena. Extensions of Previous Work and Applications in Industrial Process," Chem. Eng. J. 1974, 8, 165. 6. Frederick, J. R. Ultrasonic Engineering; John Wiley and Sons: New York, 1965. 7. Sadeghi, M.-A.; Sadeghi, K. M.; Kuo, J. F.; Jang, L . K.; Yen, T. F. "Treatment of Carbonaceous Materials," U.S. Patent 4 765 885, 1988. 8. Kuo, J. F.; Sadeghi, K. M . ; Jang, L. K.; Sadeghi, M.-A.; Yen, T. F. "Enhancement of Bitumen Separation From Tar Sand by Radicals in Ultrasonic Irradiation," Appl. Phys. Comm. 1986, 6(2), 205. 9. Chan, M.; Sharma, M . M.; Yen, T.F. "Generation of Surface Active Acids in Crude Oil for Caustic Hooding Enhanced Oil Recovery," Ind. Eng. Chem. Process Des. Dev. 1982, 21, 580. 10. Chan, M . "Interfacial Activity in Alkaline Flooding Enhanced Oil Recovery," Ph.D. Dissertation, USC, Los Angeles, 1980. 11. Chan, M . ; Yen, T.F. "Role of Sodium Chloride in the Lowering of Interfacial Tension Between Crude Oil and Alkaline Aqueous Solution," Fuel, 1981, 60, 552. 12. Dunning, H. N.; Moore, J. W.; Denekas, M . O. "Interfacial Activities and Porphyrin Contents of Petroleum Extracts," Ind. Eng. Chem. 1953, 45, 1759. 13. Dodd, C. G.; Moore, J. W.; Denekas, M . O. "Metallifeorus Sub stances Adsorbed at Crude Petroleum-Water Interfaces," Ind. Eng. Chem., 1952, 44, 2585. 14. Huang, C. "Studies of Phosphatidylcholine Vesicles. Formation and Physical Characteristics," Biochemistry, 1969, 8, 344. 15. Sadeghi, K. M.; Sadeghi, M.-A.; Kuo, J. F.; Jang, L . K.; Yen, T. F. "Self-Propogated Surfactants Formed During Separation of Bitu men From Tar Sands Using an Alkaline Solution and Sonication," Presented at ACS, 1987 Pacific Conference on Chemistry and Spec troscopy, October 28-30, 1987. 16. Sadeghi, M.-A.; Jang, L . K.; Kuo, J. F.; Sadeghi, K. M.; Palmer, R. B.; Yen, T. F. "A New Extraction Technology for Tar Sand Produc tion," The 3rd UNITAR/UNDP Inernational Conference on Heavy Crude and Tar Sand; AOSTRA: Alberta, 1988, p 739. 17. Yen, T. F. "The Role of Asphaltene in Heavy Crude and Tar Sands," The Future of Heavy Crude and Tar Sands; McGraw Hill: New York, 1981, p 174. 18. Dickie, J. P.; Haller, M . N.; Yen, T. F. "Electron Microscopic Inves tigations on the Nature of Petroleum Asphaltics," J. Colloid Interface ScL, 1969, 29(3), 475.



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19. Yen, T. F. "Structural Differences Between Asphaltenes Isolated from Petroleum and from Coal Liquid," Chemistry of Asphaltenes; Bunger, J. W.; Li, N . C., Eds.; Advances in Chemistry Series No. 195; American Chemical Society: Washington, D.C., 1981, p 39. 20. Yen, T. F. "Present States of the Structure of Petroleum Heavy Ends and Its Significance to Various Technical Applications," ACS, Div. Petrol. Chem., Prepr. 1972, 17(4), F102. 21. Ravey, J. C.; Duconret, G.; Espinat, D. "Asphaltene Macrostructure by Small Angle Neutron Scattering," Fuel, 1988, 67, 1560. 22. Kotlyar, L . S.; Ripmerster, J. A.; Sparks, B. D.; Woods, J. "Com parative Study of Organic Matter Derived from Utah and Althabasca Oil Sands," Fuel, 1988, 67, 1529. 23. Tissot, B. P.; Welte, O. H. Petroleum Formation and Occurrence; Springer Verlag: New York, 1984, 2nd Ed. 24. Yen, T. F. "Chemical Aspects of Interfuel Conversion," Energy Sources, 1973, 1, 117. 25. Yen, T. F. "Long-Chain Alkyl Substituents in Native Asphaltic Molecules," Nature, Phy. Sci., 1971, 233, 36. 26. Fendler, J. H., "Microemulsions, Micelles, and Vesicles for Mem brane Mimetic Photochemistry," J. Phys. Chem., 1980, 84, 1485. 27. Briggs, D. E.; Addongton, D. V.; Mckeen, J. A . Coal IV, CEP Technical Manual, 1978. 28. Pollack, S. S.; Yen, T. F. "Structural Studies of Asphaltics by X-Ray Small Angle Scattering," Anal. Chem., 1970, 42, 623. 29. Dwiggins, C. W., Jr. "A Small Angle X-Ray Scattering Study of the Colloidal Nature of Petroleum," J. Phys. Chem., 1965, 69, 3500. 30. Hartshorne, N . H.; Stewart, A . Crystals and the Polarizing Microscope; Arnold: London, 1970. 31. Hartshorne, N. H . The Microscopy of Liquid Crystal; Microscope Publications Ltd: London, 1974. 32. Tiddy, G . J. T. "Surfactant-Water Liquid Crystal Phases," Physics Reports (Review Section of Physics Letters) 1980, 57(1), 1. 33. Franses, E . I.; Talmon, Y.; Scriven, L . E.; Davis, H . T.; Miller, W. G. "Vesicle Formation and Stability in the Surfactant Sodium 4(1'- Heptylnonyl) benzenesulfonate," J. Colloid Interface Sci.,1982, 86(2), 449. 34. Fendler, J. H. Membrane Mimetic Chemistry; Johy Wiley & Sons: New York, 1982. 35. Puig, J. E.; Franses, E . I.; Yeshayahu, T.; Davis, H . T.; Miller, W. G.; Scriven, L . E . "Vesicular Dispersion Delivery Systems and Surfactant Waterflooding," Soc. Petrol Eng. J., 1982, February, 37. RECEIVED January 26, 1989


Microscopic Studies of Surfactant Vesicles Formed During Tar Sand

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