Asphaltene Aggregation: Influence of Composition of Copolymers

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Asphaltene aggregation: influence of composition of copolymers based on styrene-stearyl methacrylate and styrene-stearyl cinnamate containing sulfate groups Luiz Carlos Magalhães Palermo, and Elizabete F. Lucas Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.6b00444 • Publication Date (Web): 13 Apr 2016 Downloaded from http://pubs.acs.org on April 18, 2016

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Asphaltene aggregation: influence of composition of copolymers based on styrene-stearyl methacrylate and styrene-stearyl cinnamate containing sulfate groups Luis C. M. Palermo1,2 and Elizabete F. Lucas1,3* 1

Federal University of Rio de Janeiro, Institute of Macromolecules, Av. Horácio Macedo, 2030, Cidade Universitária, 21941598, RJ, Brazil - Phone# 552139387033. 2

Halliburton, Technological Park, R. Paulo Emídio Barbosa, 485, Cidade Universitária, 21941907, RJ, Brazil 3

Federal University of Rio de Janeiro, COPPE, Program of Materials and Metallurgy

Engineering, Av. Horácio Macedo, 2030, block F, Cidade Universitária, 21941598, RJ, Brazil, [email protected]

* Corresponding author: [email protected]

ABSTRACT. The stabilization of asphaltenes by chemical additives, resulting mainly from the action of amphiphilic molecules with low molar mass, has been widely used in the petroleum industry. Polymer materials can also be used as asphaltene stabilizers, although they can act as stabilizers or flocculants in function of their molar mass and/or composition. Asphaltene flocculation is also important in deasphalting crude oil or recovering polyaromatic molecules to be used as filler in polymer composites. In order to better understand the factors that affect the action of polymers on asphaltene phase behavior, we investigated a new family of compounds based on styrene-octadecyl methacrylate and styrene-octadecyl cinnamate, with varied sulfonation degrees. The results show that besides molar mass, the content of long pendant hydrocarbon chains (C18), the sulfonic groups content in the molecule and the polymer concentration directly influence the type of effect (stabilization or flocculation) on asphaltenes. The sulfonation of copolymers increases their stabilizing action by promoting stronger interaction of the additive with the asphaltene molecules by sulfonic groups. However, an excess of sulfonic groups promotes a reversal of this behavior, from stabilizing to flocculating, because a large amount of sulfonic groups in the same molecule brings the asphaltene molecules together and induces their aggregation. Keywords: Styrene-stearyl methacrylate; styrene-stearyl cinnamate; asphaltene stabilization/flocculation; asphaltene precipitation onset; near infrared spectrometry

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INTRODUCTION Crude oil is a complex mixture of hydrocarbons, classified in different groups, such as paraffins, aromatics, naphthenes, resins and asphaltenes. Among these substances, paraffins and asphaltenes stand out as mainly responsible for organic deposition. The asphaltenes in particular, classified as the most polar fraction of petroleum, cause problems during production and refining by clogging lines and equipment and stabilizing water-in-oil emulsions, hindering the demulsification of crude oil. 1-17 The aggregation of asphaltenes occurs when the solubilizing power of the liquid phase becomes insufficient to keep them dispersed and the asphaltene particles pass from an agglomerated state, corresponding to average diameter of 0.2 µm, to a precipitated state, with average diameter of about 3 µm.1-2,18 Investigation of the stabilization/flocculation of asphaltenes is therefore of great scientific and technological interest. The asphaltene precipitation onset, determined by n-heptane titration and near infrared spectroscopy (NIR) detection, can be used to identify formation of asphaltene particles. Although this method does not determine the size of the particles, it measures the amount of n-heptane required to form particles that are detectable by NIR. So, it can be inferred, from the shift of the asphaltene precipitation onset if the system is more or less stable, related to the amount of n-heptane required to provoke precipitation. The displacement of the asphaltene precipitation onset induced by an additive can be related to its stabilization/flocculation behavior: higher or lower onset values than that found for the pure petroleum/model system would correspond, respectively, to stabilizing or flocculating action. By definition, asphaltenes are soluble in aromatic hydrocarbons (like benzene and toluene) and insoluble in n-alkanes (like n-pentane, n-hexane and n-heptane). n-Heptane has been used in this kind of test to normalize the results.4,9,19-22

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Chemical inhibitors are often used to prevent asphaltene deposition.19,23-24 Among these substances, the literature mentions molecules with relatively low molar mass and amphiphilic characteristics, such as alkylphenols with long hydrocarbon chains and sulfonic acids with long hydrocarbon chains. In relation to the dispersion of asphaltenes, amphiphilic compounds have proved to be efficient. The stabilization of asphaltenes is enhanced with increasing acidity of the polar group and longer alkyl chains. For example, p-alkylphenols have stronger stabilization effect than compounds with shorter chains, possibly due to the steric stabilization effect.25 Stabilization has also been attributed to the long alkyl radical by other authors.26 The dispersion power of the surfactants 4-dodecylbenzenesulfonic acid (DBSA), nonylphenol (NP) and 4-dodecyl resorcinol (DR), besides toluene and natural petroleum resins, have also been investigated.27 It has been verified that the effect of additives in stabilizing the asphaltenes present in the suspension is related mainly to the interaction between the molecules of the additive and the asphaltenes. The adsorption of amphiphilic compounds on the surface of asphaltene molecules and the acid-base interaction are the main reasons why asphaltenes remain stable, so that compounds with strong acidity are more efficient in destabilizing them.27 However, the efficiency of these molecules appears to depend on the type of oil and the asphaltene precipitation-inducing agent (n-alkanes or CO2).22

Derivatives

of

alkylbenzene,

ionic

liquids28

and

compounds

based

on

phthalocyanine29 also have been cited in the literature as promoting additive interactions with asphaltene molecules. The employment of vegetable oils as asphaltene dispersants is an inexpensive and green alternative. Cashew nut shell liquid (CNSL) and cardanol have been investigated as asphaltene stabilizers with satisfactory results.20,30 Vegetable oils (coconut, sweet almond,


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andiroba and sandalwood) and organic acids (linoleic, caprylic and palmitic) have dispersant behavior, associated with the length of the hydrocarbon chain.31 In contrast to the stabilization, the asphaltenes, flocculation is very important to the deasphaltation of the crude oil and for the recovery polycyclic aromatics, which can be applied as fillers in polymer composites, for example.32-33 The flocculation of asphaltenes can be achieved by the same kind of molecular interactions as those occurring for asphaltene stabilization, but the molar mass, composition and concentration affect this behavior. For example, polymers with controlled molar mass and specific content of polar groups in their structure act as stabilizer.19,24,25,27,34 Variation of the molar mass and composition of copolymers with the same structure can alter their behavior from stabilizer to flocculant.19-23-24 In one study, evaluation of polymers based on cardanol, obtained by addition polymerization, revealed a relation between the molar mass of the additive and its asphaltene stabilization/flocculation action.20 Polycardanol (PCN) and sulfonated polystyrene (SPS), with varied sulfonation degrees, were investigated as flocculants/stabilizers.21 Some molecules act as stabilizers and others as flocculants. It appears that besides the influence of molar mass, as mentioned previously,20 the content of acid groups in the same molecule and the concentration of polymer added also have an influence, with larger quantities of acid groups promoting flocculation of asphaltenes. These previous studies have shown there is a transition threshold for stabilization-flocculation of asphaltenes in function of the characteristics of the polymers, but additional information is necessary to better understand this relationship. Therefore, the objective of this study was to assess a new family of compounds based on styrene-methacrylate (long-chain) and styrene-cinnamate (long-chain), with varied sulfonation degrees, and to study the influence of the characteristics of the


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molecules on their action to stabilize/flocculate asphaltenes, monitoring it by NIR since this technique is quite fast, simple and reliable.

EXPERIMENTAL PART Materials Asphaltic residue was donated by Petrobras (source: Duque de Caxias Refinery); 99.5% n-heptane (used as received) and technical grade toluene (distilled at 100 ºC and dried under silica) were supplied by Vetec Química Fina (Duque de Caxias); and tetrahydrofuran HPLC/Spectro grade (used as received) was supplied by Tedia Brasil (São Paulo). The copolymers based on styrene-stearyl methacrylate and styrene-stearyl cinnamate, sulfonated and unsulfonated (Figure 1), were synthesized and characterized in a previous work35 and their specifications are reported in Table 1.

Extraction of the asphaltene fractions The asphaltenes were extracted from an asphaltic residue (ASPR) sample by solubility difference, using n-heptane as flocculant and toluene as solvent, with a Soxhlet extractor. The procedure is described in detail elsewhere in the literature.4,6,9 The C71 asphaltene fraction extracted from the ASPR was characterized and used to prepare model solutions of asphaltene in dry toluene, at concentration of 1 % wt/v.

Characterization of asphaltene fraction C7I The asphaltene structure was characterized by Fourier-transform infrared spectroscopy (FTIR) with a Varian Excalibur FTS 3100 spectrophotometer, using film casting in a KBr cell. The spectrum was scanned from 4000 to 400 cm-1 with resolution of 4 cm-1 at room


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temperature. The molar mass was measured by matrix-assisted laser desorption/ionizationtime-of-flight mass spectrometry (MALDI-TOF-MS) with a Shimadzu AXIMA Confidence spectrometer with positive ionization and a N2 laser, operating at 200 Hz. Fifty microliters of THF was used to prepare a solution of approximately 2 µg/mL, which was deposited on the support and evaporated at room temperature before the analysis. In these tests, we did not use a matrix to assist the ionization, due to the presence of ionizable groups in the asphaltene structure. The spectrogram obtained was treated with the standard software installed in the device.

Asphaltene precipitation onset The precipitation onset of the asphaltenes, from examining the model systems containing 1 %wt/v of asphaltenes in toluene, was determined by near infrared (NIR) spectrophotometry in a Bruker Matrix-F instrument at a wavelength of 1600 nm, using an external probe with 5mm optical path inserted in a flask containing 10 mL of the sample (model system of asphaltenes in toluene with concentration of 1% wt/v). A Jasco PU-2087 chromatographic pump was used to add the flocculant (n-heptane) at a flow of 2mL/min.4,9,36-37 In the beginning, the absorbance decreases with increasing flocculant volume because of the dilution of the system. Then, when the amount of flocculant is enough to induce asphaltene precipitation, the absorbance starts increasing due the presence of aggregates in the system. The volume of flocculant related to the lowest absorbance value was divided by 10 to express the asphaltene precipitation onset in terms of mL of flocculant per 1.0 mL of sample. The model systems were evaluated pure and with the addition of the selected copolymers (Table 1), at concentrations of 0.01, 0.025, 0.05 and 0.1 %wt/v. The standard deviation was 0.05 mL of n-heptane per 1.0 mL of model solution.


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RESULTS AND DISCUSSION Characterization of asphaltene fraction C7I Figure 2 presents the FTIR for the asphaltene fraction C7I, showing: bands in the region of 2920 and 2840 cm-1 (A), referring to the axial deformation of the CH2 and CH3 groups; a band at 1580 cm-1 (B), related to the C=C and C=O bonds; bands at 1450 (C) and 1372 cm-1 (D), attributed to the symmetric and asymmetric axial deformations of the CH3 group, respectively; a band at 1032 cm-1 (E), referring to the sulfoxide group (C2S=O); bands at 840 and 790 cm-1 (F), referring to the aromatic structure present in the asphaltene molecules and the out-of-plane deformation of the C-H bond of the ring; and a band at 730 cm-1 (G), referring to the aromatic hydrogen atoms. This spectrum is similar to those presented in the literature for other asphaltene samples.4,5,13,18,38 The use of mass spectrometry to determine the molar mass of asphaltenes has been increasing in recent years.39-41 The result of this analysis indicated that the molar mass of the asphaltene fraction C7I extracted was in the range of 100 to 1000 g/mol, with a maximum peak at 370 g/mol. This result is in accordance with those obtained previously.5

Influence of copolymers on the asphaltene precipitation onset of the model-system The precipitation onset of asphaltenes is related to the volume of the flocculant (nheptane) necessary to start precipitation. The results of this analysis have been used to assess the precipitation potential of asphaltenes.4,9,14,18 The main limitations of the method to determine the precipitation onset of asphaltenes utilizing flocculant titration with monitoring of the absorption intensity by NIR are related to two factors: (i) in viscous oil samples, it is only possible to identify the effect of dilution of


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the sample, not the precipitation of asphaltenes; and (ii) the interference of the particles present in crude oil (from the reservoir rock formation) is not considered.7,42 However, these drawbacks are not found when analyzing model systems, as those containing asphaltenes in toluene analyzed here. Figure 3 presents the graph of absorbance in function of volume of n-heptane added to the pure model system, which presented a precipitation onset value of 1.30 mL of n-heptane per 1.00 mL of model solution. This number was obtained from the inflection point of the curve, i.e., the minimum absorbance value, where the effect of formation of aggregates starts to overcome the effect of dilution of the system. Note that the value taken from the curve in Figure 3 was divided by 10 since 10 mL of the model solution was used. The systems containing copolymer presented curves with similar profiles. The asphaltene precipitation onset results are reported in Figures 4 and 5, respectively, for styrene-stearyl methacrylate copolymers (SSMA-mass1, SSMA-mass2, SSMA-mass4, SSMA-mass5 and SSMA-sol2) and styrene-stearyl cinnamate copolymers (SSC-mass1 and SSC-mass2), both families with and without the presence of varied concentrations of sulfonic groups. An increase or reduction in relation to the value of 1.30 mL of n-heptane per 1.0 mL of model system would indicate whether the additive acted as a stabilizer or flocculant, respectively. By analyzing the results for the styrene-stearyl methacrylate copolymers without sulfonic groups, the highest precipitation onset values were obtained at the lowest concentration (0.01 %wt/v). Due to the predominant aromatic character of asphaltenes, the interaction with copolymers should occur by the aromatic ring of the styrene. In an aromatic solvent (toluene), intramolecular interactions of the hydrocarbon pendent chains of the copolymers is expected. As polymer concentration increases, the contact among molecules also increases, bringing


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together the asphaltene molecules and reducing the stability, i.e., the asphaltene precipitation onset decreases. The copolymer with lowest content of hydrocarbon chains (SSMA-mass1) was the only one that acted as a flocculant (Figure 4a – sulfonation degree = 0%): at concentration of 0.01%, there was no variation in the precipitation onset, while raising the dosage to 0.1% led to a reduction in the precipitation onset in relation to the pure model system (from 1.30 to 1.16 mL of n-heptane per 1.0 mL of model solution), with its flocculant character accentuating with increased concentration. This behavior is based on the interactions explained above. There is a probably a strong interaction between this copolymer and asphaltenes due to the high content of styrene in its structure. However, there are not enough long hydrocarbon chains to stabilize the system. The other copolymers without sulfonic groups did not have flocculant action in the concentration range evaluated, while the strongest stabilizing action was obtained by SSMAmass4 (Figure 4c – sulfonation degree = 0%) at 0.01%, where the precipitation onset rose from 1.30 to 1.56 mL of n-heptane per 1.0 mL of model solution. We expected the increase in content of long hydrocarbon chains to provide an increase in the steric stabilization. However, the action of the copolymers did not appear to be associated only with the average content of hydrocarbon chains in the molecules, since copolymer SSMA-mass2 (Figure 4b), with composition similar to that of SSMA-mass4, showed less pronounced stabilizing action (1.47 mL of n-heptane per 1.0 mL of model solution). In a previous study,35 it was observed that SSMA-mass4 was soluble in solvents presenting solubility parameters in a broader range, thus enabling it to exhibit a more amphiphilic character, which is also coherent with its stronger stabilizing action. Besides this, SSMA-mass4 is the copolymer with the lowest average molar mass, an aspect that was associated with better stabilizing action in a previous


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study.20 In any event, a significant increase in the content of hydrocarbon chains appears to reverse the behavior of the additive: samples SSMA-mass5 (53/47) and SSMA-sol2 (60/40), with the highest content of pendant hydrocarbon chains, had weaker stabilizing action than observed for SSMA-mass4 (82/18). The additive SSMA-mass1 had flocculant action at all sulfonation degrees (39.1 – 55.0%) and concentrations tested (0.01 – 0.1%) (Figure 4a). Therefore, we believe there is a relationship between the sites available in the dispersants for interaction with the asphaltene molecules and their efficiency. Copolymer SSMA-mass1 has, besides the inserted sulfonic groups, greater availability of aromatic rings, which also interact with the polycondensed rings of the asphaltenes, so that the lower proportion of hydrocarbon segments conferred by the lower stearyl methacrylate in the copolymer’s structure diminishes the steric impediment and thus favors the formation of asphaltene aggregates. For all the other structures (SSMA-mass2, SSMA-mass4, SSMA-mass5 and SSMAsol2), we observed a shift of the precipitation onset to higher sulfonation degrees, in general occurring at the lowest dosage (0.01%). This behavior is probably associated with the increase in the amphiphilic character of the molecules due to the presence of sulfonic groups. However, for sulfonation degrees above 50% the behavior reversed, with a reduction of the asphaltene precipitation onset, characteristic of flocculant action. Hence, it can be inferred that a threshold exists for the content of sulfonic groups, at which the copolymer shifts from acting as a stabilizer to being a flocculant. This concentration limit of sulfonic groups was observed in previous studies,21,43 regarding the application of sulfonated polystyrene as an asphaltene dispersant/flocculant. The pictorial representation proposed previously21 is now supported by the results obtained for the current copolymers.


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The most significant stabilizing actions (precipitation onset values of up to 1.8 mL of nheptane per 1.0 mL of model solution) were observed for the SSMA-mass2 sulfonated structure (Figure 4b), with sulfonation degree of 16.6%, at concentrations of 0.01, 0.025 and 0.5%. This indicates that the performance of the molecule is associated with a stronger relationship between the polar and non-polar groups in the polymer’s final structure. Besides this, the distribution of the sulfonic groups in the additive’s structure appears to influence the shift of the asphaltene precipitation onset. The heterogeneous distribution of acid groups after sulfonation is reported in literature.44 For the styrene-stearyl cinnamate copolymers without the presence of sulfonic groups (Figures 5a and 5b, respectively for SSC-mass1 and SSC-mass2), the results were virtually the same, with precipitation onset values shifted to slightly higher values at the lowest concentration (0.01%). The increase in stabilizing action with higher content of hydrocarbon chains (from 7 to 15 mols) confirmed the increase in the additive’s stabilizing action, as observed for the styrene-stearyl methacrylate family of copolymers. The sulfonated samples also presented flocculant action, as discussed previously. However, this behavior was observed for samples with lower sulfonation degrees in comparison to the styrene-stearyl methacrylate samples. This behavior can be related to the fact that styrene-stearyl cinnamate has a higher content of aromatic groups than the other family of copolymers, and these groups can also interact with the asphaltene molecules. The overall results evidence a sulfonation degree that represents the stabilizationflocculation transition behavior. Since this transition seems to be related also to the amphiphilic character of the molecule, the percentage of sulfonation that induces transition behavior depends on the copolymer composition.


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CONCLUSIONS The introduction of long hydrocarbon chains (C18) in the polystyrene structure produces molecules able to promote steric stabilization of asphaltenes, which can interact with the copolymers through the ester and aromatic groups. The copolymer’s behavior is related to the content of hydrocarbon chains and molar mass: very low or very high concentrations of long hydrocarbon chains appear to impair the additive’s stabilizing action. The sulfonation of copolymers increases their stabilizing action by promoting stronger interaction of the additive with the asphaltene molecules by means of the sulfonic groups. However, an excess of sulfonic groups promotes a reversal of this behavior, from stabilizing to flocculating, and the sulfonation degree where this reversal occurs depends on the copolymer’s structure. Under the conditions analyzed, the most pronounced stabilizing action was obtained for the styrenestearyl methacrylate samples (81/19 mol/mol) with sulfonation degree of 16.6%, at concentrations of 0.01, 0.025 and 0.05%. In turn, the strongest flocculant action was obtained for the styrene-stearyl methacrylate samples (95/5 mol/mol) with sulfonation degrees of 39 and 55%, at concentration of 0.1%.

ACKNOWLEDGEMENTS We thank the Brazilian research agencies CNPq, CAPES and FAPERJ, as well as the National Petroleum, Natural Gas and Biofuels Agency (ANP) and Petrobras for support.

REFERENCES (1) Gray, M. R. Upgrading Petroleum Residues and Heavy Oils; Marcel Dekker: New York, 1994.


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(2) Mullins, O. C.; Sheu, E. Y.; Hammami, A.; Marshall, A. G. Asphaltenes, heavy oils, and petroliomics; Springer:New York, 2007. (3) Ramalho, J. B. V. S.; Lechuga, F. C.; Lucas, E. F. Quim. Nova 2010, 33, 1664-1670. (4) Garreto, M. S. E.; Gonzalez, G.; Ramos, A. C.; Lucas, E. F. Chem. & Chem. Technol. 2010, 4, 317-323. (5) Honse, S. O.; Ferreira, S. R.; Mansur, C. R. E.; Gonzalez, G.; Lucas, E. F. Quim. Nova 2012, 35, 1991-1994. (6) Honse, S. O.; Mansur, C. R. E.; Lucas, E. F. J. Braz. Chem. Soc. 2012, 23, 2204-2210. (7) Mansur, C. R. E.; Melo, A. R.; Lucas, E. F. Energy Fuels 2012, 26, 4988-4994. (8) Fan, Y.; Simon, S.; Sjoblom, J. Colloids Surf. A 2010, 366, 120–128. (9) Garreto, M. S. E.; Mansur, C. R. E.; Lucas, E. F. Fuel 2013, 113, 318-322. (10) McKenna, A. M.; Donald, L. J.; Fitzsimmons, J. E.; Juyal, P.; Spicer, V.; Standing, K. G.; Marshall, A. G.; Rodgers, R. P. Energy Fuels 2013, 27, 1246-1256. (11) Altoé, R.; Oliveira, M. C. K.; Lopes, H. E.; Teixeira, C.; Cirilo, L. C. M.; Lucas, E. F.; Gonzalez, G. Colloids Surf. A 2014, 445, 59-66. (12) Poveda, J. C.; Molina, D.; Martinez, H.; Florez, O.; Campillo, B. Energy Fuels 2014, 28, 735-744. (13) Ferreira, S. R.; Barreira, F. R.; Spinelli, L.; Seidl, P.; Leal, K. Z.; Lucas, E. F. Quim. Nova in press. DOI: 10.5935/0100-4042.20150172 . (14) Ferreira, S. R.; Louzada, H. F.; Gonzalez, G.; Lucas, E. F. Energy Fuels 2015, 29, 7213– 7220. (15) Maia Filho, D. C.; Ramalho, J. B. V. S.; Spinelli, L.; Lucas, E. F. Colloid Surf. A 2012, 396, 208-212.


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(16) Maia Filho, D. C.; Ramalho, J. B. V. S.; Lucas, G. M. S.; Lucas, E. F. Colloid Surf. A 2012, 405, 73-78. (17) Castillo, J.; Ranaudo, M. A.; Fernández, A.; Piscitelli, V.; Maza, M.; Navarro, A. Colloids Surf. A 2013, 427, 41-46. (18) Oliveira, G. E. Comportamento de fases de paraffins, asphaltenes e ácidos naftênicos de petroleum e influência da presença de aditivos poliméricos. D.Sc. Thesis, Universidade Federal do Rio de Janeiro, Rio de Janeiro, 2006. (19) Lucas, E. F.; Ferreira, L. S.; Khalil, C. N. Polymers Applications in Petroleum Production, in: Mark, H. F. (Ed), Encyclopedia of Polymer Science and Technology, John Wiley & Sons: New York, 2015. (20) Moreira, L. F. B.; Lucas, E. F.; Gonzalez, G. J. Appl. Polym. Sci. 1999, 73, 29–34. (21) Lima, A. F.; Mansur, C. R. E.; Lucas, E. F.; Gonzalez, G. Energy Fuels 2010, 24, 23692375. (22) Ibrahim, H. H.; Idem, R. O. Energy Fuels 2004, 18, 743-754. (23) Amro, O. M. J. Petrol. Sci. Eng. 2005, 46, 243-252. (24) Kelland, M. A. Production Chemicals for the Oil and Gas Industry; CRC Press: New York, 2009. (25) Chang, C. L.; Fogler, H. S. Langmuir 1994, 10, 1758-1766. (26) Ramos, A. C. S. J. Petrol. Sci. Eng. 2001, 32, 201– 216. (27) Al-Sahhaf, T. A.; Fahim, M. A.; Elkilani, A. S. Fluid Phase Equilib. 2002, 194/197, 1045-1057. (28) Hu, Y. F.; Guo, T. M. Langmuir 2005, 21, 8168-8174. (29) Mena-Cervantes, V. Y.; Hernandez-Altamirano, R.; Buenrostro-Gonzalez, E.; Beltran, H. I.; Zamudio-Rivera, L. S. Energy Fuels 2011, 25, 224-231.


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(30) Moreira, L. F. B.; González, G.; Lucas, E. F. Polimeros 1998, 3(jul/set), 46-54. (31) Junior, L. C. R.; Ferreira, M. S.; Ramos, A. C. S. J. Petrol. Sci. Eng. 2006, 51, 26–36. (32) Satake, A.; Miyajima, Y.; Kobuke, Y. Chem. Mater. 2005, 17, 716-724. (33) Wu, H.; Kessler, M. R. RSC Advances 2015, 5, 24264-24273. (34) Lucas, E. F.; Mansur, C. R.; Spinelli, L.; Queirós, Y. G. C. Pure Appl. Chem. 2009, 81, 473-494. (35) Palermo, L. C. M.; Souza Junior, N. F.; Silvino, A. C.; Gentili, D.; Lucas, E. F. J. Appl. Polym. Sci. 2016, 133, 43112. (36) Kallevik, H.; Hansenb, S. B.; Sæthera, Ø.; Kvalheima, O. M.; Sjöblom, J. J. Dispers. Sci. Technol. 2002, 21, 245-262. (37) Ostlund, J. A.; Nydén, M.; Auflem, I. H.; Sjöblom, J. Energy Fuels 2003, 17, 113-119. (38) Oliveira, G. E.; Mansur, C. R. E.; Lucas, E. F.; González, G.; Souza, W. F. J. Dispers. Sci. Technol. 2007, 28, 1-8. (39) Herod, A. A.; Bartle, K. D.; Kandiyoti, R. Energy Fuels 2008, 22, 4312-4317. (40) Mullins, O. C.; Martínez-Haya, B.; Marshall, A. G. Energy Fuels 2008, 22, 1765-1773. (41) Hurt, M. R.; Borton, D. J.; Choi, H. J.; Kenttämaa, H. I. Energy Fuels 2013, 27, 36533658. (42) Henriques, C. B.; Winter, A.; Koroishi, A. T.; Maciel Filho, R.; Bueno, M. I. M. S. Quim. Nova 2011, 34, 424-429. (43) Mazzeo, C. P. P. Desenvolvimento de polímeros para floculação de asfaltenos de petróleo, M.Sc. Thesis, Universidade Federal do Rio de Janeiro, 2010. (44) Kucera, F.; Jancar, J. Polym. Eng. Sci. 1998, 38, 783-792.


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Table 1. Copolymers based on styrene-stearyl methacrylate and styrene-stearyl cinnamate35 Code

Molar composition

Sulfonation degrees

Sty/Stearyl

(%)

by NMR-1H SSMA-mass1

95/5

126,000

2.84

0.0, 39.1, 55.0

SSMA-mass2

81/19

136,000

4.34

0.0, 16.6, 38.9, 57.4

SSMA-mass4

82/18

67,880

4.62

0.0, 26.0, 51.4, 66.6

SSMA-mass5

53/47

92,300

2.87

0.0, 20.6, 34.4

SSMA-sol2

60/40

123,000

2.10

0.0, 19.3, 40.3

SSC-mass1

93/7

63,600

2.30

0.0, 22.4, 40.2, 62

SSC-mass2

85/15

72,400

1.80

0.0, 14.8, 27.1, 31.1


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Figures Captions

Figure 1. Structures of (a) styrene-stearyl methacrylate and (b) styrene-stearyl cinnamate, sulfonated and unsulfonated Figure 2. Infrared absorption spectrum of asphaltene fraction C7I. Figure 3. Absorbance curve in function of n-heptane volume for the model solution of asphaltene fraction C7I in toluene at 1%m/v, obtained by near infrared (NIR) spectrometry at 1600 nm. Figure 4. Asphaltenes precipitation onset in function of additive concentration for styrene (STY) - stearyl methacrylate (SMA) copolymers: (a) SSMA-mass1 (STY/SMA 95/5), (b) SSMA-mass2 (STY/SMA 81/19), (c) SSMA-mass4 (STY/SMA 82/18), (d) SSMA-mass5 (STY/SMA 53/47) and (e) SSMA-sol2 (STY/SMA 60/40). Figure 5. Asphaltenes precipitation onset in function of additive concentration for styrene (STY) -stearyl cinnamate (CMA) copolymers: (a) SSC-mass1 (STY/CMA 93/7) and (b) SSC-mass2 (STY/CMA 85/15).


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Figure 1. Structures of (a) styrene-stearyl methacrylate and (b) styrene-stearyl cinnamate, sulfonated and unsulfonated


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Figure 2. Infrared absorption spectrum of asphaltene fraction C7I.


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Figure 3. Absorbance curve in function of n-heptane volume for the model solution of asphaltene fraction C7I in toluene at 1%m/v, obtained by near infrared (NIR) spectrometry at 1600 nm.


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Figure 4. Asphaltenes precipitation onset in function of additive concentration for styrene (STY) - stearyl methacrylate (SMA) copolymers: (a) SSMA-mass1 (STY/SMA 95/5), (b) SSMA-mass2 (STY/SMA 81/19), (c) SSMA-mass4 (STY/SMA 82/18), (d) SSMA-mass5 (STY/SMA 53/47) and (e) SSMA-sol2 (STY/SMA 60/40).


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Figure 5. Asphaltenes precipitation onset in function of additive concentration for styrene (STY) -stearyl cinnamate (CMA) copolymers: (a) SSC-mass1 (STY/CMA 93/7) and (b) SSC-mass2 (STY/CMA 85/15).


Asphaltene Aggregation: Influence of Composition of Copolymers

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