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An elemental composition and FT-IR spectroscopy analysis of crude oils and their fractions Bartlomiej Gawel, Mona Eftekhardadkhah, and Gisle Øye Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/ef402286y • Publication Date (Web): 03 Feb 2014 Downloaded from http://pubs.acs.org on February 3, 2014
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An elemental composition and FT-IR spectroscopy analysis of crude oils and their fractions Bartłomiej Gaweł, Mona Eftekhardadkhah, Gisle Øye* Ugelstad Laboratory, Department of Chemical Engineering, Norwegian University of Science and Technology (NTNU), N-7491 Trondheim, Norway *Corresponding author:
[email protected] Phone: (+47) 73 59 41 35, Fax: (+47) 73 59 40 80 Abstract Detailed compositional analysis of nine crude oils and their SARA fractions were carried out by elemental analysis and FT-IR spectroscopy. The crude oils had a broad range of physicochemical properties. The largest difference in composition was found in the asphaltene fractions of the oils, followed by the resin fractions. These fractions had significantly higher abundancy of oxygen and nitrogen hetero atoms than the saturate and aromatics fractions. Furthermore, the lightest crude oils had highest oxygen content in the asphaltene fraction, while it was highest in the resin fraction for the heaviest oils. PLS regression models suggested that the total acid number was primarily associated with carboxylic acids in aliphatic structures and that high abundancy of nitrogen and oxygen particularly in the resin fraction enhanced the total base number. It is believed that the detailed structural information provided here will help to improve the understanding of the interfacial properties of the crude oils. Keywords: Crude Oil Characterisation, FT-IR Analysis, Elemental Analysis, Multivariate Analysis
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1. Introduction Separation of crude oil and water is crucial during processing of petroleum, and much research has been focused on understanding separation of water-in-crude oil emulsions 1. From a water management and environmental point of view, destabilisation of crude oil-in-water emulsions is important in terms of purification of produced water and clean-up of oil spills 2,3. Drop size distributions and coalescence rates are important factors for the separation efficiency of emulsions, and these are influenced by interfacial tension and interfacial rheology 4, 5. Low interfacial tension between crude oil and water can result in small drop sizes, while formation of interfacial viscoelastic layers can oppose coalescence of drops. Both phenomena will result in increased emulsion stability, and consequently it is important to have knowledge about the indigenous species in crude oils and how they affect the interfacial properties.
Typical characterisation of crude oils involves separation into its SARA fractions, i.e. saturates, aromatics, resins and asphaltenes. The common separation procedure entails initial precipitation of asphaltenes and high-performance liquid chromatography (HPLC) separation of the remaining fractions. Since the technique is based on polarity differences between the constituents, the presence of heteroatoms like oxygen, nitrogen and sulphur will strongly influence the fractionation and precipitation. The type and extent of heteroatoms will strongly influence the interfacial activity 6, 7 as well as water solubility 8-10 of molecules from the various fractions. However, there is not necessarily a correlation between the amount of the fractions in the crude oils and the interfacial activity or water solubility. This means that it is beneficial to obtain further structural information about the fractions.
However, there is not necessarily a correlation between the amount of the fractions in the crude oils and the interfacial activity or water solubility. In addition molecular size will influence both the water solubility and interfacial phenomena in terms of diffusion rates and conformational relaxation at the interface11. This means that it is beneficial to obtain further structural information about the fractions.
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It is well-known that resins and asphaltenes are the most interfacially active components in crude oils 12-14. Typically, these fractions contain components with acidic and/or basic functionalities. Acidic crude oil components, often referred to as naphthenic acids, have been reported to have high interfacial activity even at low concentrations 5,7,15. The naphthenic acids are complex mixtures of various carboxylic acids with different structure and number of acidic groups16, 17. The amount of acids in crude oils is commonly determined by potentiometric titration and given as the total acid number (TAN). However, the method does not provide any structural information about the compounds. Advanced techniques like high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) can be used to obtain this 18-20. Also the amount of basic crude oil components can be determined by potentiometric titration 21, and particularly pyridinic structures have been reported to influence the properties of oil-water interfaces22, 23.
The physicochemical characterization of crude oils is often limited to SARA fractionation and determination of total acid and base numbers. This quantitative information does not necessarily provide information about the interfacial properties that can be anticipated. The aim of this work was to investigate the chemical composition and structural properties of individual crude oil fractions in detail. Nine crude oils were fractionated and analysed by elemental analysis and FTIR spectroscopy. Multivariate data analysis was used to elucidate correlations between these analyses and TAN and TBN values.
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2. Experimental 2.1 Crude oils Nine crude oils, denoted from A to I were analyzed with respect to saturates, aromatics, resins, and asphaltenes (i.e. SARA fractionations), total acid number (TAN), total base number (TBN), density and viscosity.
2.2 SARA Fractionation SARA fractionation was performed according to previously reported procedures 24. Initially asphaltenes were precipitated in n-hexane (three parallels, each of 4 g of crude oil diluted in 160 mL of solvent. The mixtures were left for mixing overnight and filtered through a 0.45-µm membrane filter (Millipore HVLP). Asphaltenes content is determined gravimetrically after solvent removal.
Further fractionation was performed using a high-performance liquid chromatography (HPLC) system with unbounded silica 15-µm 21.2 × 250 mm and amino 10-µm 21.2 × 50 mm columns 24
. 5 mL of the asphaltene extracted samples were diluted in n-hexane (corresponding to 0.6 g of
crude oil) and injected into a 20 mL/min flow (isocratic) of filtered and degassed n-hexane. The saturate fractions were collected during the first 3-5 minutes, while the aromatic fractions were collected as they left the amino precolumn (after 15 min) and from the amino precolumn by dichloromethane backflush up to 23 minutes after sample injection. The resin fractions were also eluted from the amino precolumn by dichloromethane backflush (retention time: 23−26 min). The weight fractions were determined gravimetrically after controlled evaporation of the solvents in N2 atmosphere. 2.3 Determination of the Total Acid and Base Number The total acid number (TAN) value of the crude oils was determined according to the D664−95 ASTM method 25. The crude oil (mass adjusted to obtain an equivalence volume close to 5 mL) was mixed with 50 mL of toluene, 50 mL of isopropanol, and 0.5 mL of water. The solution was titrated with 0.1 M tetrabutylammonium hydroxide dissolved in a mixture of isopropanol and methanol 10:1 (v/v). The titration was controlled by a Titrando unit (Metrohm) fitted with a
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6.0229.100 LL solvotrode with 0.4 M tetraethylammonium bromide in ethylene glycol as the electrolyte (Metrohm). The TAN value was calculated by the following equation: TAN =
M KOH CVeq moil
where MKOH is the molar weight of potassium hydroxide, C is the molar concentration of the titrant solution, Veq is the equivalence volume and moil is the mass of crude oil. The TBN value was determined by a method similar to the one described by Dubey and Doe 26. The sample (mass adjusted to obtain an equivalence volume close to 3−5 mL) was solubilised in 40 mL of methylisobutyl ketone and titrated with 0.025 M perchloric acid in acetic acid. 10 mL of titrant was added every 3 min in 0.1 ml increments. The titration was controlled by a Titrando unit (Metrohm) fitted with a 6.0229.100 LL solvotrode with 2 M LiCl in ethanol as the electrolyte (Metrohm). The TBN value was calculated from the following equation: TBN =
M KOH CVeq moil
where MKOH is the molar weight of potassium hydroxide, C is the molar concentration of the perchloric acid solution, Veq is the equivalence volume and moil is the mass of crude oil. 2.4 Density Measurements The density of the crude oils was measured with a DMA 5000 laboratory density meter (Anton Paar, Austria) at 20 oC.
2.5 Viscosity Measurements The viscosity of the crude oils was measured with a MCR 301 laboratory Rheometer (Anton Paar, Austria). The measurements were done at 20 oC using CC-27 geometry.
2.6 Elemental Analysis Carbon, hydrogen, nitrogen, sulfur and oxygen contents were determined using a CHNSO EA 1108 Elemental Analyser, Fisons Instruments. The measurements were carried out at the Oil and Gas Institute (Kraków, Poland).
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2.7 FT-IR Spectroscopy FT-IR spectra were recorded on a spectrometer (Bruker Optics) equipped with an Attenuated Total Reflection (ATR) cell. Spectra were collected between 4000 cm-1 and 600 cm-1, with 4 cm1
resolution. In most cases, a drop of sample was placed directly on the ATR cell. Some of the
samples were dissolved in CH2Cl2, in order to easily place small amounts of sample on the cell, and measured after solvent evaporation. The band intensities were integrated using the Fityk software.
2.8 Multivariate Data Analysis – Partial Least Square (PLS) Regression PLS regression is a data decomposition method where so-called latent variables are used to explain the maximal variance and maximize the covariance between two groups of variables (X and Y) 27. A model is constructed that relates predictors (X) variables to one or more response (Y) variables, and regression coefficients are used to identify the most important predictor variables in the model 28. One PLS regression model was made by relating the elemental analysis (C, H, N, O S) of the various fractions to the TBN values. The FT-IR spectra of the resin and asphaltene fractions were related to the TAN values in another model. In both cases, the prediction variables were weighted by the amount of the appropriate fractions. The number of latent variables was restricted to two, in order to avoid overfitting of the data. The analyses were performed with the Unscrambler X 10.1 software (Camo Software, Norway).
3. Results and discussion 3.1 Characterisation by elemental analysis Table 1 summarizes the physicochemical properties of the investigated crude oils. The density of the oils ranged from 0.81 to 0.94 g/cm3. Oil samples A, E and F had distinctly lower density than the remaining oils. These three samples were also recognised to have the lowest amounts of resins and highest amounts of saturates. An asphaltene content of 13.9 wt% for crude oil C was considerably higher than for the other oils, for which the amounts ranged from 0.1 to 2.5 wt%. Crude oil C was also the only oil where the amount of asphaltenes was higher than for the resins. The TBN values ranged from 0.6 to 4.4 mg/g. Eight of the samples had higher TBN values than TAN values and were considered to be basic in nature. Five of the oils (A, C, D, E and F) had low TAN values, i.e. between 0.3 and 0.5 mg/g, while the remaining oils had values between 1.4
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and 2.7 mg/g. The highest TAN value was observed for sample H, which was the only acidic crude oil.
Elemental analyses were carried out for the crude oils and for each of their SARA fractions. The C/H ratios of the crude oils are shown in Table 1. High C/H ratio indicated less hydrogen present in the samples and was attributed to higher aromaticity and higher extent of ring condensation. More hydrogen, i.e. lower C/H ratio, was associated with the presence of aliphatic compounds. Five of the crude oils (B, E, F, H and I) had relatively similar C/H ratios within the range of 0.50 to 0.53. Higher ratios (> 0.56) were seen for crude oils C, D and G, demonstrating overall higher aromaticity. Nevertheless, the C/H ratios are generally lower than those reported for bitumen samples 29. The C/H ratio of crude oil A was considerably lower than for the other oils, indicating that the sample had overall more aliphatic character.
The C/H ratios of the SARA fractions of the oils are shown in Figure 1, and all fell into the following sequence: saturates < aromatics ≈ resins < asphaltenes. As expected, low ratios were seen for the saturate fraction for all the oils. The minor differences between C/H ratios within the saturate fractions were likely caused by variations in chain length, degree of branching and extent of cyclic compounds. The similarity also revealed that the substantially lower C/H ratio observed for crude oil A as a whole was due to the high amount of saturates, not a distinctive difference in the composition of the saturate fraction. Generally, the aromatics and resins fractions had similar aromaticity for all the oils. This could suggest that these fractions had similar extent of methylene moieties. The highest structural variance in terms of aromaticity was seen between the asphaltene fractions of the crude oils.
The oxygen content of the crude oils is given in Table 1. Crude oil B had the highest amount of oxygen (1.62 wt%) of the oils. The acid number of this oil was also high. Furthermore, crude oils A and C high oxygen contents (1.1-1.2 wt%), but low total acid numbers. The remaining oils had similar amounts of oxygen within the range of 0.47 to 0.84 wt%. Some of these oils (D, E and F) had low acid numbers, while it was higher for the other oils (G, H and I). This demonstrated large variation in the fraction of oxygen associated with acidic groups between the oils.
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Figure 2 shows the oxygen content of the SARA fractions of the oils. Low amounts of oxygen were observed in the saturate fraction of all the oils. This could be due to the presence of oxygen atoms in non-polar ether compounds. Incomplete separation of fractions could also be an explanation. The oxygen content was higher in the aromatics fractions, and significantly higher in the resin and asphaltene fractions. For some of the oils, the asphaltene contained more oxygen than the resins. These crude oils (A, B, F and I) also had the lowest asphaltene content (i.e. small fractions of highly polar asphaltenes) and low viscosity. The crude oils were the resin fractions had highest oxygen content generally corresponded to the oils with highest viscosity.
The nitrogen content of the crude oils was lower than the oxygen content, as seen in Table 1. Crude oil H stood out with higher nitrogen content than the other oils, while it was very low for crude oil A and C. Figure 3 shows the amount of nitrogen in the SARA fractions. For all the crude oils most of the nitrogen was present in the resin and asphaltene fractions. Low amounts of nitrogen were seen in the aromatics fraction for some oils, while none of the oils had detectable nitrogen in the saturate fraction.
Generally, the crude oils had low amounts of sulfur, as seen in Table 1. A notable exception was crude oil C, which contained about 6 wt% sulfur. As shown in Figure 4, the sulfur is more or less evenly distributed between the aromatics, resin and asphaltene fractions. For crude oil C, however, the asphaltenes had markedly more sulfur than the aromatics and resin fractions. None of the crude oils had sulfur in the saturate fraction. This indicated that this element generally was present within heterocyclic ring systems of polyaromatic compounds (i.e. thiophenic compounds) rather than within aliphatic chains like thiols, sulfides and disulfides.
3.2 Characterisation by FT-IR spectroscopy The FT-IR spectra were relatively similar for all the crude oils as seen in Figure 5. All the band assignments are summarised in Table 2. Most of the absorption bands were assigned to different types of C-H vibrations30. The strong bands at 2950, 2920, 2850, and 1446 and 1377 cm-1 corresponded to stretching and bending vibrations for aliphatic –CH2 and –CH3 groups, respectively. The band around 1600 cm-1 was associated with aromatic C=C stretching vibrations, while the bands between 900 and 700 cm-1 were assigned to various aromatic C–H in-
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plane and out-of plane bending vibrations 30. The band around 1700 cm-1 was attributed to the stretching vibrations of carbonyl groups, predominantly in carboxylic acids (see below). The intensity of this band was generally low, but the highest intensity was observed for the samples with high TAN values (samples B, G, I, H) and high resins content. Figure 6 shows the FT-IR spectra from 1800 to 600 cm-1 of the SARA fractions of the crude oils. The spectra for the saturate fractions are similar for all the oils and are dominated by the aliphatic –CH2 and –CH3 bending vibrations at 1446 and 1377 cm-1, Figure 6A. In addition, a band around 730 cm-1, appeared, which has been attributed to long alkyl chains; (CH2)n with n > 4 30. Also the spectra of the aromatics fractions were quite similar for the oils, Figure 6B. The characteristic ring vibrations were seen around 1600 cm-1 and in the range between 900 and 700 cm-1. Some differences in the relative intensities of the bands indicated structural variations. The aliphatic bending vibrations at 1446 and 1377 cm-1 showed that alkyl groups are substituted on the aromatic rings, while the stretching vibration of the carbonyl group at 1700 cm-1 was most pronounced in sample A, B and F. Significant variations in band intensities were seen in the resin fractions, Figure 6C. This indicated more pronounced structural differences between the crude oils in this fraction. In addition to the characteristic aliphatic and aromatic vibrations, several bands corresponding to polar functional groups were observed. The C=O stretching band around 1700 cm-1 was clearly seen in all the samples, and was most pronounced for the fraction from crude oil H, i.e. the only acidic oil. The band around 1031 cm-1 can be assigned to C-O stretching vibrations of ethers and alcohols as well as sulfoxides 31. The relatively low sulfur content (except for crude oil C), made it likely that the band was mostly dominated by the C-O stretching vibrations. This was further supported by the presence of OH stretching around 3300 cm-1 (not shown) and the bands located around 1306 cm-1, 1260 cm-1 and 1160 cm-1 which can be ascribed to C-O vibrations in esters, acids, and alcohols. It should also be noted that any residuals of solvent could result in C-H out-of-plane wagging and C-Cl stretching vibrations at 1260 cm-1 and 740 cm-1, respectively. The band assignments for the asphaltene fractions were similar as described for the resin fractions, but the variations in relative band intensities and the broadness of the bands (i.e. structural variation) were larger, Figure 6D.
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The ratios between intensities of some characteristic absorption bands were used to further investigate structural characteristics of the fractions, Figure 7. The extent of aromaticity in the fractions were evaluated by considering the ratio between the bands associated with aromatic C=C stretching (around 1600 cm-1) and aliphatic C-H bending (around 1460 cm-1). The aromatic character was markedly more pronounced in the resin and asphaltene fractions than in the aromatics fractions, Figure 7A. This is different than what was observed from the elemental analysis, where the aromatic character of the aromatics and resin fractions were similar (Figure 1). This originated from different hereroatoms content in the aromatics and resins fractions. Higher heteroatom percentage in the resins fraction elevates C/H ratio due to lower hydrogen content, however do not affect significantly the peaks ratio. Furthermore, the ratio between intensities of the C=O stretching vibration (around 1700 cm-1) and aliphatic C-H bending (around 1460 cm-1) was used to evaluate the extent of carbonylic groups in the various fractions, Figure 7B. Only three of the oils (A, B and C) had low amounts of carbonyls in the aromatics fractions. Other oxygen containing functional groups must then account for most of the oxygen observed in these fractions (Figure 2). Significant amounts of carbonyl were, however, seen in the resin and asphaltene fractions, even though the variation between the oils was large. The majority of the oils had more carbonyl in the resin fraction than in the asphaltene fraction.
3.3 PLS regression analysis The predicted TBN values are plotted versus the measured values in Figure 8. Crude oil C was identified as an outlier (probably due to the high sulfur content) and was not included in further analysis. The R2 value of the model was 0.96, while 76 % of the variation in the X variables (elemental composition of the fractions) was used to predict 96 % of the variation in the Y variables (TBN values). This indicated that the model preformed quite well. The regression coefficients for the first latent variable in the model are shown in Figure 9. Variables with positive coefficients tend to enhance TBN values in the model, while the opposite is the case for negative coefficients. The signs of the coefficients for each variable were similar for the aromatics, resin and asphaltene fractions. However, the absolute and relative magnitudes varied
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between the fractions. It is clear that the resin fraction was most important for the model. High amounts of nitrogen and oxygen in this fraction gave high TBN values. Detailed structural analyses (by FT-ICR MS) have shown that both N1 and N1O1 are abundant heteroatom classes in resin fractions 19, 20. In these studies the nitrogen class species were attributed to carbazolic type of compounds, while the oxygen atom in the N1O1 class species were considered to be hydroxyl rather than furan-like cyclic ethers. Furthermore, the amount of sulphur did not influence the model, while high values of the C/H ratio opposed high TBN values. The latter suggested that more condensed aromatic structures contributed less to TBN values, even though it should be expected that the basic functionalities are present within aromatic structures 21. Finally, the model showed that the aromatics fraction was more important for TBN values than the asphaltene fraction, despite higher abundancy of nitrogen and oxygen in the latter. This might be attributed to the larger amounts of aromatics in the crude oils.
The model relating the FT-IR spectra of the fractions to the TAN values (excluding crude oil C) had a R2 value of 0.87, while 67 % of the variation in the X variables was used to explain 87 % of the variation in the Y variables. The regression coefficients for both the latent variables in the model are shown in Figure 10. There was little information in the coefficients for the first latent variable (blue line), probably due to light scattering effects during analysis. For the second latent variable (blue line), the coefficients corresponding to the carbonyl stretching around 1700 cm-1 were most important for the TAN value. Positive contributions were seen from the coefficients associated with C-O stretching vibrations around 1260 cm-1 and 1160 cm-1 as well. Negative coefficients around 1600 cm-1 corresponded to aromatic C=C stretching vibrations. Based on this, the model suggested that the TAN values were related with carboxylic acids associated with aliphatic rather than aromatic structures. This is in good agreement with the accepted structural properties of naphthenic acids 32.
4. Conclusions Detailed compositional analysis of nine crude oils and their SARA fractions were carried out. The crude oils had a broad range of physicochemical properties. The largest difference in composition was found in the asphaltene fractions of the oils, followed by the resin fractions.
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These fractions had significantly higher abundancy of oxygen and nitrogen hetero atoms than the saturate and aromatics fractions. Furthermore, the lightest crude oils had highest oxygen content in the asphaltene fraction, while it was highest in the resin fraction for the heaviest oils. PLS regression models suggested that the total acid number was primarily associated with carboxylic acids in aliphatic structures and that high abundancy of nitrogen and oxygen particularly in the resin fraction enhanced the total base number. Acknowledgment The authors are grateful to the industrial sponsors (ConocoPhillips Skandinavia, ENI Norge, Schlumberger Norge Divison, M-I EPCON, Statoil Petroleum and Total E&P Norge) of the joint industrial program “Produced Water Management: Fundamental Understanding of the Fluids” for financial support.
5. References: (1) Sjöblom, J.; Aske, N.; Auflem, I. H.; Brandal, O.; Havre, T. E.; Saether, O.; Westvik, A.; Johnsen, E. E.; Kallevik, H., Adv. Colloid Interface Sci. 2003, 100, 399-473. (2) Zahed, M. A.; Aziz, H. A.; Isa, M. H.; Mohajeri, L., Clean: Soil Air Water 2012, 40, 262267. (3) Ahmadun, F. l.-R.; Pendashteh, A.; Abdullah, L. C.; Biak, D. R. A.; Madaeni, S. S.; Abidin, Z. Z., J. Hazard. Mater. 2009, 170, 530-551. (4) Maldonado-Valderrama, J.; Martin-Rodriguez, A.; Galvez-Ruiz, M. J.; Miller, R.; Langevin, D.; Cabrerizo-Vilchez, M. A., Colloids Surf., A 2008, 323, 116-122. (5) Arla, D.; Sinquin, A.; Palermo, T.; Hurtevent, C.; Graciaa, A.; Dicharry, C., Energy Fuels 2006, 21, 1337-1342. (6) Varadaraj, R.; Brons, C., Energy Fuels 2007, 21, 195-198. (7) Muller, H.; Pauchard, V. O.; Hajji, A. A., Energy Fuels 2009, 23, 1280-1288. (8) Eftekhardadkhah, M.; Reynders, P.; Øye, G., Chem. Eng. Sci. 2013, 101, 359-365. (9) Eftekhardadkhah, M.; Øye, G., Energy Fuels 2013, 27, 5128-5134. (10) Eftekhardadkhah, M.; Øye, G., Ind. Eng. Chem. 2013, 52, 17315-17321. (11) Rane, J. P.; Harbottle, D.; Pauchard, V.; Couzis, A.; Banerjee, S., Langmuir 2012, 28, 99869995.
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(12) Mullins, O. C., Energ Fuels 2010, 24, 2179-2207. (13) Spiecker, P. M.; Gawrys, K. L.; Trail, C. B.; Kilpatrick, P. K., Colloids Surf., A 2003, 220, 9-27. (14) Poteau, S.; Argillier, J.-F. O.; Langevin, D.; Pincet, F. D. R.; Perez, E., Energy Fuels 2005, 19, 1337-1341. (15) Brandal, O.; Sjöblom, J.; Øye, G., J. Dispersion Sci. Technol. 2004, 25, 367-374. (16) Clemente, J. S.; Fedorak, P. M., Chemosphere 2005, 60, 585-600. (17) Simon, S.; Nordgard, E.; Bruheim, P.; Sjöblom, J., J. Chromatogr., A 2008, 1200, 136-143. (18) Hu, Q.-L.; Liu, Y.-R.; Liu, Z.-L.; Tian, S.-B.; Xu, Z.-H., Chin. J. Anal. Chem. 2010, 38, 564-568. (19) Cho, Y.; Na, J.-G.; Nho, N.-S.; Kim, S.; Kim, S., Energy Fuels 2012, 26, 2558-2565. (20) Shi, Q.; Hou, D.; Chung, K. H.; Xu, C.; Zhao, S.; Zhang, Y., Energy Fuels 2009, 24, 25452553. (21) Simon, S.; Nenningstand, A. L.; Herschbach, E.; Sjöblom, J., Energy Fuels 2010, 24, 10431050. (22) Spildo, K.; Blokhus, A. M.; Andersson, A., J. Colloid Interface Sci. 2001, 243, 483-490. (23) Nenningsland, A. L.; Simon, S.; Sjöblom, J., Energy Fuels 2010, 24, 6501-6505. (24) Hannisdal, A.; Hemmingsen, P. V.; Sjöblom, J., Ind. Eng. Chem. Res. 2005, 44, 1349-1357. (25) ASTM D664-95 1995. (26) Dubey, S. T.; Doe, P. H., Spe Reservoir Eng. 1993, 8, 195-200. (27) Esbensen, K. E., Multivariate Data Analysis In Practice, Como, 2002. (28) Geladi, P.; Kowalski, B. R., Anal. Chim. Acta 1986, 185, 1-17. (29) Yoon, S.; Bhatt, S.; Lee, W.; Lee, H.; Jeong, S.; Baeg, J.-O.; Lee, C., Korean J. Chem. Eng. 2009, 26 (1), 64-71.(29) Castro, L. V.; Vazquez, F., Energy Fuels 2009, 23, 1603-1609. (30) Castro, L. V.; Vazquez, F., Energy Fuels 2009, 23, 1603-1609. (31) Boukir, A.; Aries, E.; Guiliano, M.; Asia, L.; Doumenq, P.; Mille, G., Chemosphere 2001, 43, 279-286. (32) Brandal, O.; Hanneseth, A. M.; Hemmingsen, P. V.; Sjöblom, J.; Kim, S.; Rodgers, R. P.; Marshall, A. G., J. Dispersion Sci. Technol. 2006, 27, 295-305.
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Page 14 of 25
Table 1: Physicochemil properties of the crude oils
A
B
C
D
E
F
G
H
I
0.81
0.92
0.94
0.91
0.81
0.82
0.92
0.88
0.9
43.2
22.3
19.0
24.0
43.2
41.0
22.3
29.3
25.7
3
78
487
18800
11
16
408
11
159
Saturates (wt%)
80.0
44.3
25.6
58.1
67.7
62.2
53.5
60.0
52.0
Aromatics (wt%)
18.0
38.8
49.6
30.7
27.1
31.2
29.9
36.0
32.0
Resins (wt%)
1.9
16.4
10.9
9.5
4.4
5.9
14.4
6.7
13.9
(wt%)
0.1
0.5
13.9
1.7
0.8
0.7
2.5
0.3
2.1
Resin/asphaltenes
19
33
0.8
6
6
8
6
22
7
TAN (mg/g)
0.4
2.3
0.5
0.3
0.3
0.3
2.2
2.7
1.4
TBN (mg/g)
0.6
4.4
1.3
1.5
1.1
1.5
2.9
0.8
3
C/H (atomic ratio)
0.44
0.52
0.58
0.56
0,51
0.5
0.56
0.52
0.53
O (wt%)
1.13
1.62
1.24
0.81
0,47
0.64
0.76
0.84
0.78
N (wt%)
