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Compositional Characterization of Bitumen/Water Emulsion Films by Negative- and Positive-Ion Electrospray Ionization and Field Desorption/Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry Lateefah A. Stanford, Ryan P. Rodgers,* and Alan G. Marshall* National High Magnetic Field Laboratory, Florida State UniVersity, Tallahassee, Florida 32310-4005, and Department of Chemistry and Biochemistry, Florida State UniVersity, Tallahassee, Florida 32306

Jan Czarnecki and Xin A. Wu Syncrude Canada Limited, Edmonton Research Centre, Edmonton, Alberta, Canada ReceiVed June 24, 2006. ReVised Manuscript ReceiVed NoVember 22, 2006

By means of electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) and automated field desorption/ionization (FD) FT-ICR MS, we identify nonvolatile nonpolar, polar acidic, and basic water-in-bitumen emulsion film stabilizers. Highly condensed aromatic basic, nonpolar, and acidic asphaltene multilayered films stabilize emulsions near or at critical bitumen concentration for asphaltene flocculation. Solvent diluent added beyond the critical dilution concentration precipitates highly condensed acidic, all basic, and most neutral species from the oil/water interface. The most abundant classes in high bitumen concentration emulsion films include neutral pure hydrocarbons and S, acidic O2 and O2S, and basic N and NS heteroatom classes. Highly abundant low bitumen concentration emulsion film stabilizers include acidic O2, O4, and O3S classes.

Introduction Oil sands and petroleum water washing for bitumen, solids, and corrosive chloride separation often result in water-in-oil emulsions. Unfortunately, stable emulsions decrease oil recovery, reduce process efficiency, and increase process costs and revenue loss. Through hydrogen bonding, surface-active species self-associate as flexible or rigid multilayered three-dimensional network films that trap water molecules in stable emulsions.1-5 Surface-active components include resins, asphaltenes, and organometallic species. Surface-active species relative concentration and sensitivity to pH, solvent type, and salt control emulsion film stability.2,6 Stable emulsion research focuses primarily on asphaltenes, the heptane-insoluble petroleum fraction, characteristically polycondensed aromatics with multiple alkyl chains and self* Address correspondence to either author. (R.P.R.) Tel: 850-644-2398. Fax: 850-644-1366. E-mail: [email protected]. (A.G.M.) Tel: 850644-0529. Fax: 850-644-1366. E-mail: [email protected]. (1) Acevedo, S.; Escobar, G.; Gutierrez, L. B.; Rivas, H.; Gutierrez, X. Interfacial rheological studies of extra-heavy crude oils and asphalteness role of the dispersion effect of resins in the adsorption of asphaltenes at the interface of water-in-crude oil-emulsions. Colloid Surf. A 1993, 71 (1), 65-71. (2) Eley, D. D.; Hey, M. J.; Lee, M. A. Rheological studies of asphaltene films adsorbed at the oil-water interface. Colloids Surf. 1987, 24 (2-3), 173-182. (3) Goual, L.; Horvath-Szabo, G.; Masliyah, J. H.; Xu, Z. H. Adsorption of bituminous components at oil/water interfaces investigated by quartz crystal microbalance: implications to the stability of water-in-oil emulsions. Langmuir 2005, 21 (18), 8278-8289. (4) Ignasiak, T. M.; Strausz, O. P. Reaction of athabasca asphaltene with tetralin. Fuel 1978, 57 (10), 617-621. (5) Moschopedis, S. E.; Speight, J. G. Investigation of hydrogen-bonding by oxygen functions in athabasca bitumen. Fuel 1976, 55 (3), 187-192.

Figure 1. Average hydrogen/carbon (H/C) ratio (calculated from all negative-ion ESI species) for 0.1-5.0% bitumen emulsion film interfacial material.

associating acidic and basic functional groups.7,8 Asphaltene polycondensed fused ring planar structure and self-associating multi-heteroatom functional groups allow asphaltenes to “stack” (6) Acevedo, S.; Escobar, G.; Ranaudo, M. A.; Khazen, J.; Borges, B.; Pereira, J. C.; Mendez, B. Isolation and characterization of low and high molecular weight acidic compounds from Cerro Negro extraheavy crude oil. Role of these acids in the interfacial properties of the crude oil emulsions. Energy Fuels 1999, 13 (2), 333-335. (7) McLean, J. D.; Kilpatrick, P. K. Effects of asphaltene aggregation in model heptane-toluene mixtures on stability of water-in-oil emulsions. J. Colloid Interface Sci. 1997, 196 (1), 23-34. (8) McLean, J. D.; Kilpatrick, P. K. Effects of asphaltene solvency on stability of water-in-crude-oil emulsions. J. Colloid Interface Sci. 1997, 189 (2), 242-253.

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Figure 2. FD neutral class relative abundances (>1%) for 0.1%, 1.0%, and 5.0% bitumen emulsion interfacial material. Neutral classes comprise hydrocarbons, thiophenes, and O2 and O4 classes that may be acidic but that may also include neutral species such as esters.

Figure 3. Double bond equivalents (DBE) distribution for FD-ionized acidic and neutral classes for 0.1%, 1.0%, and 5.0% bitumen emulsion interfacial material.

as supramolecular aggregates. Asphaltene solvation controls oil/ water (o/w) interface adsorption. Aromatic solvents and resins at high concentration relative to asphaltene solvate asphaltenes.8,9 Resins are the fraction of oil soluble in 80:20 toluene:MeOH v/v. Resins are lower in aromaticity and heteroatom content than asphaltenes. Solvated “free” asphaltene molecules have less surface activity than asphaltene aggregates and do not adsorb to the o/w interface.7,10 Paraffinic solvents and resins in low (9) Gafonova, O. V.; Yarranton, H. W. The stabilization of water-inhydrocarbon emulsions by asphaltenes and resins. J. Colloid Interface Sci. 2001, 241 (2), 469-478. (10) Yarranton, H. W.; Hussein, H.; Masliyah, J. H. Water-inhydrocarbon emulsions stabilized by asphaltenes at low concentrations. J. Colloid Interface Sci. 2000, 228 (1), 52-63.

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concentration solvate asphaltenes poorly. Near and at critical concentration in poor solvents, asphaltenes flocculate into aggregates with a surface activity high enough to adsorb to the o/w interface. Further dilution past the critical point cause aggregates to grow too large for interface adsorption, and they precipitate out of solution.7,10 Furthermore, an increase in asphaltene heteroatomic functional groups, alkyl side chain branching, aromatic cores, condensation of aromatic cores, molecular weight, and oil metal content increases asphaltene precipitation in paraffinic solvents.11 Increase in normal alkyl side chain length decreases propensity for precipitation in paraffinic solvents.7,8,11-13 Emulsion film composition ultimately governs stability and rheologic properties. Adsorbed multilayered colloidal asphaltene aggregates stabilize rigid emulsion films, whereas adsorbed resins yield flexible emulsion interfacial material (IM).14-16 Here, we apply high-resolution ESI and FD FT-ICR MS for nonvolatile polar and nonpolar heteroatomic species compositional characterization of flexible and rigid bitumen/water emulsion interfacial material. FT-ICR MS is capable of attaining mass resolving power, m/∆m50% > 200,000 (∆m50% is the mass spectral full peak width at half-height), from 225 < m/z < 1000, making it possible to differentiate compounds of the same nominal mass but differing exact mass with an accuracy to within 1%) for 0.1%, 0.5%, 1.0%, 3.0%, and 5.0% bitumen emulsion interfacial material.

Figure 5. Relative isoabundance contoured van Krevelen plot for negative-ion ESI oxygen-containing classes from 0.1%, 0.5%, 1.0%, 3.0%, and 5.0% bitumen emulsion interfacial material.

Materials and Methods Samples. Material adsorbed to emulsified water droplets was collected by a procedure developed by Wu.15 In brief, heavy water (D2O) emulsions were created with 0.1%, 0.5%, 1.0%, 3.0%, and 5.0% heptol (50:50 v/v heptane:toluene) diluted Athabasca of Alberta, Canada, bitumen (34 wt % resins and ∼17 wt %

asphaltenes). The emulsion was placed on top of plain water and centrifuged. Heavy water emulsion droplets broke through the oil/ (21) Schaub, T. M.; Hendrickson, C. L.; Quinn, J. P.; Rodgers, R. P.; Marshall, A. G. Instrumentation and method for ultrahigh resolution field desorption ionization Fourier transform ion cyclotron resonance mass spectrometry of nonpolar species. Anal. Chem. 2005, 77 (5), 1317-1324.


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Figure 6. Relative isoabundance-contoured plots of double bond equivalents vs carbon number for negative-ion ESI O1-containing class compounds from 0.1%, 0.5%, 1.0%, 3.0%, and 5.0% bitumen emulsion interfacial material.

water interface and formed a cake at the bottom of the plain water. The cake was collected, dried, and weighed. In the following text, we refer to the dried cake as the emulsion interfacial material (IM). Sample Preparation for ESI FT-ICR MS and Automated FD FT-ICR MS. Sample preparation for the analysis of petrochemicals by negative-ion ESI FT-ICR MS has been reported previously.17 We diluted each sample to 1 mg/mL in 50:50 chloroform:MeOH rather than 50:50 toluene:MeOH because chloroform (unlike toluene) is sufficiently polar to dissolve the emulsion material completely. No acid or base was added for ESI or FD because samples with high asphaltene content tend to precipitate on addition of acid or base. Each sample was delivered to the ionization source via a syringe pump at a rate of 400 nL/min through a 50 µm i.d. fused silica micro ESI needle under typical ESI conditions (2.5 kV; tube lens, 350 V; and heated capillary current, 4 A).22 For automated FD, samples were diluted to approximately 0.1 mg/mL in methylene chloride and continually applied to the emitter (85-100 nL/min) by a syringe pump (kdScientific Inc., New Hope, PA) through a 50 cm long, 10 µm i.d. fused silica capillary (Polymicro Technologies, LLC, Phoenix, AZ); 0.1%, 0.5%, 1.0%, 3.0%, and 5.0% samples were run by negative- and positive-ion ESI. The data for all five samples are shown for negative-ion ESI and FD, but (for simplicity) only the 0.1%, 1.0%, and 5.0% samples for FD and positive-ion ESI are given to show the general overall transitions in compositional and DBE trends for the species that compose the interfacial material. Mass Spectrometry. Each o/w interfacial sample was analyzed with a home-built 9.4 T 22 cm horizontal room temperature bore diameter (Oxford Corp., Oxford Mead, UK) ESI FT-ICR mass spectrometer at the National High Magnetic Field Laboratory.23 A Modular ICR Data Acquisition system (MIDAS) was used to collect (22) Emmett, M. R.; White, F. M.; Hendrickson, C. L.; Shi, S. D. H.; Marshall, A. G. Application of micro-electrospray liquid chromatography techniques to FT-ICR MS to enable high-sensitivity biological analysis. J. Am. Soc. Mass Spectrom. 1998, 9 (4), 333-340.

and process ICR data.23,24 Calibrant ions were generated by electrospray from Agilent (Palo Alto, CA) HP mix. Ions were accumulated externally in a linear octapole ion trap for 20 s and transferred through rf-only multipoles to a 10 cm diameter, 30 cm long open cylindrical Penning ion trap.25 Octapole ion guides were operated at 1.6 MHz with 100 Vp-p rf amplitude and a 900 µs transfer period.26 Broadband frequency-sweep (chirp) dipolar excitation (∼70 kHz to 641 kHz at a sweep rate of 150 Hz/µs and peak-to-peak amplitude of 190 V) was followed by direct mode image current detection to yield 4 Mword time-domain data. Two hundred fifty time-domain data sets were co-added and Hanning apodized, followed by a single zero-fill before fast Fourier transformation and magnitude calculation. Frequency was converted to mass-to-charge ratio by the quadrupolar electric potential approximation.27,28 Field desorption experiments were conducted with a home-built FD FT-ICR mass spectrometer.21 The system is based on a 9.4 T, (23) Senko, M. W.; Hendrickson, C. L.; PasaTolic, L.; Marto, J. A.; White, F. M.; Guan, S. H.; Marshall, A. G. Electrospray ionization Fourier transform ion cyclotron resonance at 9.4 T. Rapid Commun. Mass Spectrom. 1996, 10 (14), 1824-1828. (24) Blakney, G. T.; van der Rest, G.; Johnson, J. R.; Freitas, M. A.; Drader, J. J.; Shi, S. D.-H.; Hendrickson, C. L.; Kelleher, N. L.; Marshall, A. G. In Further ImproVements to the MIDAS Data Station for FT-ICR Mass Spectrometry, 49th ASMS Conference on Mass Spectrometry and Allied Topics, Chicago, IL, 2001. (25) Senko, M. W.; Hendrickson, C. L.; Emmett, M. R.; Shi, S. D. H.; Marshall, A. G. External accumulation of ions for enhanced electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. J. Am. Soc. Mass Spectrom. 1997, 8 (9), 970-976. (26) Hendrickson, C. L.; Quinn, J. P.; Emmett, M. R.; Marshall, A. G. In Quadrupole Mass Filtered External Accumulation for Fourier Transform Ion Cyclotron Resonance Mass Spectrometry, 48th ASMS Conference on Mass Spectrometry and Allied Topics, Long Beach, CA, 2000. (27) Ledford, E. B.; Rempel, D. L.; Gross, M. L. Space-charge effects in Fourier-transform mass-spectrometrysmass calibration. Anal. Chem. 1984, 56 (14), 2744-2748.

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Figure 7. Relative isoabundance-contoured plots of double bond equivalents vs carbon number for negative-ion ESI O2 class compounds from 0.1%, 0.5%, 1.0%, 3.0%, and 5.0% bitumen emulsion interfacial material.

155 mm horizontal bore diameter actively shielded superconducting solenoidal magnet (Magnex Scientific, Oxford, England). Ions are generated by a commercial field desorption ionization source and emitters (Linden CMS, Leeste, Germany). All experiments except the 0.1% bitumen sample were analyzed by automated FD FTICR MS29 to allow signal averaging of up to 100 scans. The 0.1% bitumen sample was analyzed by single scan FD FT-ICR MS due to sample-induced problems with automated FD FT-ICR MS. Three rf-only octapole ion guides transport externally generated positively charged ions through three stages of differential pumping. Ions are transported through a 76 mm long transfer octapole to a 160 mm long accumulation octapole where they are collected for 10-20 s by collisional cooling with helium. Ions are transported through the magnetic field gradient by a 1450 mm long transfer octapole to an open cylindrical (70 mm diameter, 212 mm long) capacitively coupled Penning ion trap.30 Trapped ions are cooled with a pulse of helium collision gas before broadband frequency sweep (chirp) excitation (200 Vp-p from 125 kHz to 500 kHz at 150 Hz/µs). Detected signals are digitized (1.2 MHz bandwidth, 4 M time-domain data) and transferred to the control PC where multiple scans (5-100) are co-added and stored for later fast Fourier transformation and frequency-to-mass conversion. Stored data sets are Hanning-apodized and zero-filled once prior to fast Fourier

transform and magnitude calculation. A modular ICR data system (MIDAS) handles instrument control, data acquisition, and data analysis.23,24 Mass Calibration. Mass spectra were frequency-to-m/z calibrated externally with respect to an Agilent G2421A electrospray “tuning mix” for all peaks of magnitude more than 3 SD of baseline noise. Externally calibrated spectra were then internally recalibrated with respect to the most abundant homologous alkylation series for each sample. All masses were then converted to the Kendrick mass scale.31 Kendrick-sorted masses were imported into Microsoft Excel for identification by a formula calculator as previously reported.32 In summary, unique molecular formulas were assigned to peaks of lowest m/z value for each Kendrick Mass Defect (KMD) series. Peaks of higher m/z ratio for the same KMD value were assigned by adding multiples of CH2 to the molecular formula. Calculations were limited to elemental compositions with e100 12C, 2 13C, 200 1H, 5 14N, 10 16O, 3 32S, and 1 34S. If more than one possible formula was generated for a specific mass, one or more could almost always be confirmed or eliminated by the presence/absence of a peak corresponding to the same elemental composition but with 13C, 18O, or 34S. All observed species were singly charged, as evidenced by unit m/z separation between mass spectral peaks corresponding to the 12Cc and 13C12Cc-1 isotopic variants for each elemental composition.

(28) Shi, S. D. H.; Drader, J. J.; Freitas, M. A.; Hendrickson, C. L.; Marshall, A. G. Comparison and interconversion of the two most common frequency-to-mass calibration functions for Fourier transform ion cyclotron resonance mass spectrometry. Int. J. Mass Spectrom. 2000, 196, 591-598. (29) Smith, D. F.; Schaub, T. M.; Hendrickson, C. L.; Rodgers, R. P.; Marshall, A. G. Automated Field Desorption FT-ICR MS for Petroleum Analysis, Proc. Amer. Soc. Mass Spectrom. Ann. Conf. on Mass Spectrometry & Allied Topics, Seattle, WA, 27 May - 2 June, 2006. (30) Beu, S. C.; Laude, D. A. Elimination of axial ejection during excitation with a capacitively coupled open trapped-ion cell for Fouriertransform ion-cyclotron resonance mass-spectrometry. Anal. Chem. 1992, 64 (2), 177-180.

Results and Discussion Critical Concentration. The average IM ion hydrogen-tocarbon (H/C) ratio is a measure of the overall emulsion film’s (31) Kendrick, E. A mass scale based on χ2 ) 14.0000 for high resolution mass spectrometry of organic compounds. Anal. Chem. 1963, 35 (13), 2146. (32) Hughey, C. A.; Hendrickson, C. L.; Rodgers, R. P.; Marshall, A. G.; Qian, K. N. Kendrick mass defect spectrum: A compact visual analysis for ultrahigh-resolution broadband mass spectra. Anal. Chem. 2001, 73 (19), 4676-4681.


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Figure 8. Relative isoabundance contoured van Krevelen plot for negative-ion ESI OxS-containing classes from 0.1%, 0.5%, 1.0%, 3.0%, and 5.0% bitumen emulsion interfacial material.

saturated versus unsaturated character.14 Saturated character increases as the H/C ratio increases. Polar acidic (i.e., all negative-ion ESI species) from 0.1 to 5.0% bitumen emulsion IM decreases in saturation with increasing percent of bitumen (Figure 1). Neutral species (see below) reflect similar H/C ratio trends; however, the nonpolars are more saturated as their H/C distribution ranges from 1.88 for 0.1% to 1.81 for 5.0% bitumen emulsion IM. The intermediate portion of the H/C versus percent of bitumen plot marks the critical dilution or critical bitumen concentration for asphaltene flocculation and a transition in interfacial film rheology.14,15 The critical concentration was observed at 1.0% bitumen in heptol for neutral and acidic species alike. In addition to H/C ratios, emulsion stabilizer class abundances change as a function of percent of bitumen (Figures 2-4). Figures 2 and 4 depict changes in nonpolar and acidic IM species with bitumen concentration. Abundance is scaled relative to the highest-magnitude peak in each mass spectrum, so that even if the absolute abundance of a given class is the same for two samples, its relatiVe abundance depends on differences in the abundances of other species. Therefore, if compounds of a given class maintain the same double bond equivalents (DBE) and alkylation values across a range of percent of bitumen emulsion IM, then any change in relative abundance for that class presumably reflects a corresponding change in the absolute abundance(s) of other species. DBE refers to the number of ring and/or double bonds calculated from the following equation:

DBE ) x - 1/2y + 1/2z + 1 for elemental composition, (C + Si)x(H + F + Cl)y(N + P)zOo,Ss (1) Figure 2 FD FT-ICR MS data reveal the dominance of nonpolar

organics in the 5.0% bitumen emulsion IM (69% pure hydrocarbons (HC) and 7% S class ions). HC and S class ion abundances are insignificant past critical dilution, as O2 (42%) and O4 (30%) classes dominate the interface. The 0.1% bitumen IM O2 class FD ions with four DBE and O4 class ions with 3 DBE are most abundant. The low O2 class DBE values of 0.1% bitumen IM from FD ions indicate naphthenic acids, which are one of the components in resins from SARA fractionation. Relative abundances for species of various DBE are shown in Figure 3. Integer DBE values (Figure 3, bottom) correspond to M+• ions and halfinteger DBE values (Figure 3, top) correspond to [M - H]+• ions.33 HC and S class ion IM depletion below the critical bitumen concentration cannot be attributed to DBE distribution because the most abundant HC (DBE 2) and S class (DBE 7) ions in 1.0-5.0% bitumen emulsion IM films fall within the same DBE range as adsorbed O2 and O4 species in the IM film at low bitumen concentration. Thus, adding paraffinic solvent past critical dilution would additionally precipitate 0.5 < DBE < 7 O2 and O4 species if DBE were the limiting factor. Therefore, we relate the high HC and S class abundances at high bitumen concentration to the composition of the bulk phase. Through resin:asphaltene heteratomic group hydrogen bonding, resins of aromaticitiy similar to that of asphaltenes partially solvate rigid emulsion stabilizing asphaltene colloids. Thus resins may co-adsorb to the interface as partially resin-solvated asphaltene aggregates.3 Similarly, bulk oil nonpolars partially solvate asphaltene aggregates, through attraction to asphaltene (33) Purcell, J. M.; Hendrickson, C. L.; Rodgers, R. P.; Marshall, A. G. Atmospheric pressure photoionization Fourier tansform ion cyclotron resonance mass spectrometry for complex mixture analysis. Anal. Chem. 2006, 78, 5906-5912.



Figure 9. Relative isoabundance-contoured plots of double bond equivalents vs carbon number for negative-ion ESI O2S class compounds from 0.1%, 0.5%, 1.0%, 3.0%, and 5.0% bitumen emulsion interfacial material.

Figure 10. Relative isoabundance-contoured plots of double bond equivalents vs carbon number for negative-ion ESI O3S class compounds from 0.1%, 0.5%, 1.0%, 3.0%, and 5.0% bitumen emulsion interfacial material.

polyaromatic fused cores and nonpolar tails.7,8 HC and S species cannot stabilize emulsions alone, as they lack polar function-

alities needed to decrease o/w interfacial tension and form bridging hydrogen bonds with water for emulsion stabilization.3


Figure 11. ESI basic (i.e., all classes that ionize by positive-ion ESI) NSO class relative abundances (>1%) for 0.1%, 1.0%, and 5.0% bitumen emulsion interfacial material.

We propose that partially HC and S class-solvated polar asphaltene aggregates account for low IM HC and S class abundance at low bitumen concentration. HC and S class IM depletion below bitumen critical concentration suggests coprecipitation as for asphaltenes aggregates. Acidic Oxygen-Containing Species. Oxygen-containing classes are the most abundant polar acidic emulsion film stabilizers, at each bitumen concentration (Figure 4). Nitrogencontaining classes are the least abundant. Nitrogen/oxygen compounds (i.e., NO, NO2, NO3) are the most abundant adsorbed nitrogen classes, indicating enhanced surface activity for species with at least one oxygen atom. We infer possible structural differences between adsorbed acidic resinous and asphaltenic species based on DBE and van Krevelen diagram aromaticity and alkylation distributions. Although FT-ICR MS

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cannot determine molecular structure, we can infer structural characteristics from ionization efficiency, carbon number, and DBE. The van Krevelen plot in Figure 5 concisely displays degree of unsaturation (aromaticity) from isoabundance contours for the hydrogen/carbon (H/C) ratio versus the oxygen/carbon (O/C) for each elemental composition containing at least one oxygen atom. Thus, the O/C ratio separates compositions horizontally by compound class (O, O2, O3, etc.) and the H/C ratio separates members of the same class with different type (DBE value) and carbon number distribution. The data shifts vertically downward with increasing DBE (i.e., increasing aromaticity). Finally, compositions with a given DBE value separate diagonally as a function of alkyl chain length.34 As for the FD data, negative-ion ESI O2 and O4 ions of low aromaticity are the most abundant Ox emulsion stabilizers at low bitumen concentration. Near the critical concentration of 1.0% bitumen, O4 ion abundance decreases. The 0.5% bitumen IM O4 class ions are more alkylated than 5.0% O4 ions, indicated by a wider O/C distribution. Ions of lower H/C ratios appear as percent of bitumen increases, confirming a shift to asphaltenic emulsion stabilization. Figure 6 illustrates changes among emulsion IM ESI polar acidic O1 class ions with respect to bitumen concentration. At critical concentration, largely polyaromatic phenolic O1 class species adsorb to the o/w interface. Polyaromatic phenols (11 < DBE < 20) in g1.0% bitumen emulsion IM, may have a sheet-like three-dimensional structure that stacks as thin rigid multilayered emulsion films. Alkylated monoaromatic phenols DBE 4) are seen in 1.0% bitumen IM, but sheet-like alkylated tri-aromatic phenols (DBE 9 and 10) are the most prevalent. DBE 2 (alkene or dicyclic) to 10 (tri-aromatic) surface-active O1 class ions occupy the o/w interface at low bitumen concentration, whereas C32-34 alkyl phenols (DBE 4) are the most abundant.

Figure 12. Relative isoabundance-contoured plots of double bond equivalents vs carbon number for positive-ion ESI basic N class compounds in 0.1%, 1.0%, and 5.0% bitumen emulsion interfacial material.



Figure 13. Relative isoabundance-contoured plots of double bond equivalents vs carbon number for positive-ion ESI basic NS class compounds in 0.1%, 1.0%, and 5.0% bitumen emulsion interfacial material.

Selective ionization of carboxylic acids by negative-ion ESI has previously been reported.18,35 ESI O2 class negative ions are presumably carboxylic acids. Unlike the phenols, 0.1% bitumen IM O2 class emulsion stabilizers have high aromatic character with fatty acids to tetra-aromatic (1 < DBE < 16) compositions contributing to flexible emulsion stability (Figure 7). Nevertheless, 1 < DBE < 11 O2 class ions are most abundant. 0.1% bitumen IM O2 class emulsion stabilizers are presumably napthenoaromatic at DBE 16. Naphthenic acids are part of the resin fraction according to SARA fractionation.36-40 Acyclic, cyclic, aromatic, and naptheno-aromatic acids compose naphthenic acid fractions.40 Distinction of O2 resins and asphaltenes may be naphtho-aromatic versus fused polyaromatic species. At g1.0% bitumen, DBE 21 O2 species adsorb to the interface. Acidic Sulfur-Containing Species. In addition to nonyl phenol, alkylbenzene sulfonates, (e.g., dodecylbenzensulfonic (34) Kim, S.; Kramer, R. W.; Hatcher, P. G. Graphical method for analysis of ultrahigh-resolution broadband mass spectra of natural organic matter, the van Krevelen diagram. Anal. Chem. 2003, 75 (20), 5336-5344. (35) Hsu, C. S.; Dechert, G. J.; Robbins, W. K.; Fukuda, E. K. Naphthenic acids in crude oils characterized by mass spectrometry. Energy Fuels 2000, 14 (1), 217-223. (36) Aske, N.; Kallevik, H.; Sjoblom, J. Determination of saturate, aromatic, resin, and asphaltenic (SARA) components in crude oils by means of infrared and near-infrared spectroscopy. Energy Fuels 2001, 15 (5), 1304-1312. (37) Gelot, A.; Friesen, W.; Hamza, H. A. Emulsification of oil and water in the presence of finely divided solids and surface-active agents. Colloids Surf. 1984, 12 (3-4), 271-303. (38) Green, J. B.; Stierwalt, B. K.; Thomson, J. S.; Treese, C. A. Rapid isolation of carboxylic-acids from petroleum using high-performance liquidchromatography. Anal. Chem. 1985, 57 (12), 2207-2211. (39) Koike, L.; Reboucas, L. M. C.; Reis, F. D. M.; Marsaioli, A. J.; Richnow, H. H.; Michaelis, W. Naphthenic acids from crude oils of campos basin. Org. Geochem. 1992, 18 (6), 851-860.

acid) are widely used in industry as asphaltene dispersents.11 In general IM OxS negative-ion aromaticity increases (decreased H/C) as percent of bitumen increases (Figure 8). At the flexible o/w interface 2 < DBE < 17 O2S compounds stabilize the emulsion (Figure 9). O2S compounds with DBE ) 17 are highly aromatic for a resin stabilized system, however O2S compounds are most abundant at 3 < DBE

Water Emulsion Films by

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