Aromatic Polyisobutylene Succinimides as Viscosity Reducers with

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Aromatic Polyisobutylene Succinimides as Viscosity Reducers with Asphaltene Dispersion Capability for Heavy and Extra-Heavy Crude Oils Tomás Eduardo Chávez-Miyauchi,*,†,‡ Luis S. Zamudio-Rivera,*,†,§ and Victor Barba-López∥ †

Grupo de Química Aplicada a la Industria Petrolera, ‡Programa de Posgrado and §Programa de Ing. Molecular, Instituto Mexicano del Petróleo (IMP), Eje Central Lázaro Cárdenas No. 152 col. San Bartolo Atepehuacan, México D.F., 07730, México ∥ Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Morelos, Av. Universidad 1001, 62209 Cuernavaca, Morelos, México S Supporting Information *

ABSTRACT: Four aromatic polyisobutylene succinimides were synthesized and evaluated as viscosity reducers for heavy and extra-heavy Mexican crude oils. Because of the asphaltenic character of Mexican crude oils, aromatic heads capable of interacting with asphaltene aggregates by π−π stacking, hydrogen-bond formation, and acid−base interactions were selected. Asphaltene dispersion−aggregate inhibition and asphaltene disaggregation effects were evaluated as promoters of the viscosity reduction effect in asphaltenic crude oils, the asphaltene disaggregation being dominant. Chemical compounds show good efficiency as asphaltene aggregation inhibitors and dispersants and as viscosity reducers. Higher efficiency than the dilution effect induced by the solvent carrier is observed. Both experiments were studied by theoretical DFT calculations. Because of the agreement between theoretical and experimental results, both mechanisms can be elucidated. Results also show that the initial asphaltene content in oils is an important parameter in the selection of chemical agents as viscosity reducers.

1. INTRODUCTION Heavy and extra-heavy oil production is gaining interest because of the increasing oil demand and the decreasing production of conventional oils. The scenario implies enormous challenges in flow assurance, where the principal objective is the prevention of heavy organic compounds precipitation and viscosity reduction. The oil industry is then facing to the development of heavy oil fields located in Latin America, specially, Colombia, Venezuela, and Mexico.1 The high viscosity of heavy oils has been attributed to the content of heavy organic compounds such as resins and asphaltenes. There are diverse studies where the oil rheology is studied in terms of resin and asphaltene content,2−6 and it has been observed that, below an asphaltene concentration of 10%, the oil shows a behavior like a diluted system where the viscosity is directly proportional to the amount of resins, while above 10% of asphaltene content, the system behaves like a concentrated system where the viscosity increases dramatically because of the entanglement of the asphaltene aggregates in the media. Mexican oils are characterized by their high viscosities and their high amount of asphaltenes,7 generally above 8%. Many chemical products have been developed as flow improvers for heavy and extra-heavy crude oils, but these compounds are designed for waxy oils and have moderate to little effect in asphaltenic oils,8−11 because asphaltenes act as nucleation centers for the wax crystal growth,12 so it is desirable that the chemical compound is capable of dispersing or breaking these aggregates. Polyisobutylene succinimides have been used as detergent− dispersants in lubricating oils, but also as asphaltene dispersants and aggregate inhibitors in oil.13−15 Also, it has been observed © 2013 American Chemical Society

that compounds with a succinimide moiety are capable of breaking asphaltene aggregates, reducing their average molecular weight.16 On the basis of these premises and assuming that by dispersing heavy organic compounds, viscosity reduction of heavy oils can be achieved, derivatives of polyisobutylene succinimides were synthesized and analyzed as asphaltene dispersants and viscosity reducers for a heavy and an extraheavy Mexican crude oils. The polyisobutylene tail was selected because of its highly branched structure that can induce steric hydrance and disorder in the system, helping the breaking of aggregates and dispersion of heavy organic compounds. As the chemical product must interact with the asphaltene, it must mimic the interactions among asphaltene aggregates like π−π stacking, hydrogen bonds, acid−base interactions, van der Waals forces, and coordination complexes,17 and it must have an acid character,18 which is desirable because of the Lewis base character of the asphaltenes. For these reasons, compounds with hydroxyl and boronic acid19 functional groups were also tested.

2. EXPERIMENTAL SECTION 2.1. Materials. Aniline, benzylamine, 3-aminophenol, 3-aminophenylboronic acid monohydrate, xylene, toluene, and n-heptane were purchased from Aldrich (at HPLC and reagent grade) and were used without further purification. PIBSA of Mn = 1098 g mol−1 was purchased from BASF and was used without further purification. The oils used for evaluations were Maya-type Mexican crude oils with two Received: October 28, 2012 Revised: February 21, 2013 Published: February 27, 2013 1994

dx.doi.org/10.1021/ef301748n | Energy Fuels 2013, 27, 1994−2001

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different API gravity values (21° and 12°, respectively), the properties of which are shown in Table 1.

The efficiency was obtained by the relation of absorbances of the test samples by the absorbance of the reference sample, eq 1

Table 1. Maya-Type Crude Oils Properties API gravity (deg) viscosity (Pa s) at 25 °C and 20 s−1 shear rate SARA analysis (wt %) saturates aromatics resins asphaltenes

%eff = oil A

oil B

21 0.723

12 29.681

18.17 28.97 41.52 11.31

03.07 30.85 48.77 17.06

Aexp A ref

× 100

(1)

The aggregate inhibition−dispersion effect due to the solvent of the samples was neglected by subtracting the efficiency of the sample with pure xylene (0.0 g L−1) from the other samples; by this way, only the effect of the chemical compounds is then observed. 2.4. Optical Microscope Images of Aggregates of Asphaltenes. Optical microscope images of the asphaltene aggregates separated by centrifugation of the dispersion−aggregation inhibition test solutions were obtained at amplification of 100 times their real size. The centrifugation process was applied to separate all the aggregates remaining in the solutions of the dispersion−aggregation inhibition test and also to promote the disaggregation effect of chemical compounds by inducing the further mixture of chemical compounds 1−4 with already formed aggregates. The experiment was performed only for the samples with 0.2 g L−1 of chemical compound. The samples were centrifugated at 2000 rpm for 25 min; asphaltenes were separated from the system by decantation and dispersed over a slide using immersion oil. Pictures of the aggregates were taken with no further amplification than that of the optical microscope. 2.5. Rheological Behavior of Crude Oil. Samples of 20 g of heavy and extra-heavy crude oils (21° and 12° API, respectively) were dosed with 0.1 g of a solution 40% w/w of compounds 1−4 in xylene obtaining a final concentration of 5 g kg−1 of additive, which corresponds to a final concentration of 2 g kg−1 of compounds 1−4. The samples were gently stirred at 50 °C for 1 h and then stabilized to ambient temperature. Apparent viscosity measurements were performed using an Anton-Paar Physica MCR-301 rheometer and a 50 mm PP50 plane measuring plate at 25, 40, 50, and 60 °C at a shear rate interval of 1.0−40.0 s−1. Low shear rates were selected due to the high viscosity of the samples. For comparative purposes, crude oil and crude oil with 5 g kg−1 of xylene were measured to be used as reference samples. 2.6. Modeling Asphaltene−Compound Interactions. The study of the interactions at a molecular scale between chemical compounds and asphaltenes with themselves and between chemical compounds and asphaltenes plays an important role in the elucidation of the mechanisms by which these compounds interact at a macromolecular scale.21,22 By these results, an understanding of how asphaltenes aggregate or how chemical agents interact with asphaltenes to inhibit or disperse asphaltene aggregates can be achieved. The aim of this section is to compare the interaction energies between the asphaltene aggregates and chemical compounds and between an asphaltene average molecule with a molecule of chemical compound. The asphaltene average structure used for the theoretical model was obtained from analytical data of the same asphaltene used in the dispersion−aggregation inhibition test. The structure was developed by Buenrostro-González et al.23,24 Molecular properties and asphaltene structure model can be observed in Table 2 and Figure 2, respectively. The molecules of compounds 1−4 have been modeled with 16 repetitive units of butylene to achieve the average molecular weight of the polymer used. Molecular structures of compounds (asp., 1, 2, 3, and 4) and their interaction pairs were optimized up to a geometrical configuration of minimal energy with the use of the DMol3 software of the console Materials Studio, version 6.0, with the following parameters: medium quality that corresponds to 2.0 × 10−5 Ha in energy, 0.004 Ha/Å in maximum force, and 0.005 Å in maximum displacement; functional GGA−PBE; method TS as correction to the contribution of dispersion energy; spin unrestricted (spin-polarized); automatic multiplicity; electric charge zero; effective core potentials treatment for internal electrons and DND base (version 3.5).25−30 The energy of the interaction pairs was calculated by the difference of total energies between monomeric and dimeric species according to eq 2

Asphaltenes were obtained from the crude oil sample with 21° API by extractions with n-heptane according to the methodology described in a previous work by Buenrostro-Gonzalez et al.20 2.2. Synthesis of Aromatic Polyisobutenyl Succinimides. The synthetic route of aromatic polyisobutenyl succinimides is summarized in Figure 1. The products were obtained as dark yellow to brown viscous liquids in good yields (82−87%). (See the Supporting Information for the synthetic procedure.)

Figure 1. Synthetic route for the preparation of compounds 1−4.

The products’ structures were confirmed by Fourier-transform infrared (FTIR) spectroscopy using a Bruker FTIR Tensor 27 spectrophotometer, following the characteristic CO stretching band at 1700−1710 cm−1 (corresponding to the succinimide moiety, unlike the CO stretching band at 1789 cm−1 corresponding to the precursor succinanhydride moiety). 2.3. Evaluation of the Asphaltene Dispersion−Aggregation Inhibiton Dispersion Activity. The asphaltene dispersion− aggregation inhibition activity of compounds 1−4 was evaluated by determination of the asphaltenes remaining in solution after induced precipitation with n-heptane through ultraviolet−visible (UV−vis) spectroscopy. The experiment is based on the premise that asphaltenes are insoluble species in n-heptane media, but can reach colloidal stability by the use of surfactants that can maintain an adequate particle size or by modulating the electrostatic forces involved in the system. All samples were prepared at ambient temperature. The reference was prepared by mixing 1000 μL of a solution of 5.0 g L−1 of asphaltenes in toluene with 9000 μL of pure toluene in a conical bottom glass tube; this sample will represent the complete dispersion of asphaltene aggregates. For the test samples, 200 μL solutions of 0.0, 1.0, 2.5, 5.0, and 10.0 g L−1 of compounds 1−4 in xylenes were mixed with 1000 μL of the 5.0 g L−1 asphaltenes solution in toluene and 8800 μL of n-heptane to obtain samples with final concentrations of compounds 1−4 from 0.0 to 0.2 g L−1. The test tubes were stirred for 5 min using a vortex system and left to rest for 24 h. After the repose time, 1000 μL of the supernatants of the samples was diluted with 4000 μL of toluene. The absorbances of diluted supernatants were obtained using 100-mm optical-path quartz cells in a UV−vis spectrometer (Perkin-Elmer Double-Beam LAMBDA-35 UV−vis spectrometer) at a selected wavelength of 410 nm.

n

ΔE inter = ΔEdimer −

∑ ΔEmonomer, i i=1

1995

(2)


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compound 2 has a methylene group that bends the head of the molecule, thus avoiding the interaction of both functional groups at the same time with the asphaltene. The difference of efficiencies between compounds 3 and 4 and compound 1 can be attributed to the hydroxyl groups in the molecule; these functional groups act as donors of hydrogen bonds, by this way, two types of interactions between the molecule and the asphaltene exist: hydrogen bonding and π−π stacking, unlike compound 1 that can only interact with the asphaltene by π−π stacking. Efficiencies of compounds 3 and 4 are very similar, but it can be observed that the efficiency of compound 4 increases very steeply with increasing concentration. This can be explained by two different reasons: first, boron acts as a Lewis acid, so it can interact with the asphaltene as well as its hydroxyl groups and the second is that there are two hydroxyl groups in 4 compared to only one hydroxyl group in compound 3. 3.2. Optical Microscope Images of Precipitated Aggregates of Asphaltenes. Optical microscope images of asphaltene aggregates are shown in Figure 4.

Table 2. Molecular Characteristics of Average Structure of Asphaltene mol formula mol wt (g mol−1) elemental analysis (%) C H no. of fused rings H/C CAa CSa CA/CS fA = CA/(CA + CS) a

C58H59NOS 818.16 85.07 7.21 10 1.02 33 25 1.32 0.57

Where CA = aromatic carbons, CS = Aliphatic carbons.

Figure 2. Asphaltene proposed for the molecular modeling.

3. RESULTS AND DISCUSSION 3.1. Asphaltene Dispersion−Aggregation Inhibiton Activity. Asphaltene dispersion−aggregation inhibition efficiencies as function of chemical compound concentration are shown in Figure 3. It can be seen that efficiencies grow rapidly

Figure 4. Optical microscope images at 100× of precipitated asphaltenes: (A) reference, (B) compound 1, (C) compound 2, (D) compound 3, and (E) compound 4 at 0.2 g L−1.

Figure 3. Asphaltenes aggregation inhibition−dispersion activity of compounds 1−4 in n-heptane medium.

for compounds 1, 3, and 4, but it is lower for compound 1 than for compounds 3 and 4, which have efficiencies above 70% at 0.2 g L−1. The notorious difference between compounds 1, 3, and 4 and compound 2 can be attributed to the spatial arrangement of the aromatic group in the head of the molecule; as the aromatic group for compounds 1, 3, and 4 are in the same axis as the succinimide group, both functional groups can interact with the plane structure of the asphaltene, while

By this series of images, it can be observed that the dispersion−aggregation inhibition effect is not directly related to the disaggregation effect of the compounds. The images show that for compounds 3 and 4 aggregates seem smaller than for compounds 1 and 2; however, asphaltene aggregates observed for compound 2 (which had no dispersion−aggregate inhibition effect) are smaller than for compound 1 and quite similar to aggregates of compound 4. This can give us also the 1996


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Figure 5. Apparent viscosity of oils dosed with chemical compounds in the range of 1−40 s−1 of shear rate. A25, A40, A50 and A60 denote oil A at 25, 40, 50, and 60 °C, respectively, and B25, B40, B50, and B60 denote oil B at 25, 40, 50, and 60 °C, respectively.

idea that compound 2 by its conformation can generate disorder in the system by steric effects. Compound 1 is

practically linear so it generates less disorder than compound 2, so the disaggregation effect is lower. 1997


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3.4. Modeling Asphaltene−Compound Interactions. Table 3 shows the calculated formation and interaction energies

For the case of compounds 3 and 4, the complexes formed must be very strong because in addition to the dispersion− aggregation inhibition effect, they can keep the aggregates small. It is important to note that although the centrifugation process involves the extraction of the solvent beneath the solid aggregates, promoting in this way the further agglomeration, the aggregates remain small with the use of the chemical compounds. 3.3. Rheological Behavior of Crude Oil. It is assumed in this work that by stabilizing the heavy organic compounds of heavy oils (by dispersing asphaltene aggregates, reducing their size, or diminishing the interaction strength among them), viscosity can be reduced. Chemical compounds have shown action in the dispersion−aggregation inhibition of asphaltenes; it has been elucidated that they also modify the electrostatic field of asphaltene aggregates31 and also can disaggregate them, so they must have effect in viscosity reduction of heavy oils. This effect must be dependent, among other properties, on the amount of asphaltenes the oil has. Two different oils were dosed with the chemical compounds: oil A with 11.31% of asphaltenes and oil B with 17.06% of asphaltenes, according to SARA analysis (n-heptane insolubles). A sample dosed with the solvent was also tested to observe the effect of the same in the viscosity reduction and to compare it with the effect alone of the chemical compounds. Results are shown in Figure 5. At first sight, it can be observed that the viscosity reduction decreases as the temperature rises in both oils; this behavior can indicate that the viscosity reduction phenomenon is still governed primarily by the thermal effect and then by the dispersion or asphaltene disaggregation mechanisms. However, by analyzing apparent viscosity curves, different effects can be elucidated. For crude A, the viscosity is reduced up to 23.25% by compound 4, at 25 °C, representing 7.12% of additional viscosity reduction compared to the solvent itself; furthermore, compounds 3 and 4 present at low temperatures a good performance in viscosity reduction that is in accordance with their efficiency as asphaltenes dispersants−aggregate inhibitors. Compound 2, unlike its efficiency as asphaltene dispersant− aggregate inhibitor, has a good performance as viscosity reducer at low temperatures, and this could be explained by its capacity to disaggregate asphaltene clusters. At higher temperatures, the efficiency as flow improvers for compounds 2−4 decreases and for compound 1 increases markedly; this behavior is because compound 1 may not have a strong interaction with asphaltenes and the energy of the system allows it to cross through the aggregates, breaking them with its highly branched aliphatic tail. Compounds 2−4 increase viscosity of the crude at 60 °C; at this temperatures, crude oil must be behaving as a diluted system where the presence of heavy molecules (as chemical compounds in this case) increases viscosity instead of decreasing it. For crude B, viscosity is always reduced by chemical compounds, and because of this, it can be assumed that the system is always in a concentrated regime. The maximum viscosity reduction achieved is 12.35% with compound 3 at 25 °C, 5.59% more than the reduction achieved by the solvent itself. In this case, the viscosity reduction effect is directly correlated to the asphaltene disaggregation at all temperatures. The dilution effect with xylene is lost at 50 °C, while the viscosity reduction remains with all the compounds even at 60 °C.

Table 3. Energetics of Model Interactions for the Asphaltene−Asphaltene, Asphaltene−Compound, and Compound−Compund Species species

total energy (kcal mol‑1) × 10‑6

ΔE (kcal mol‑1)

asp. 1 2 3 4 asp.−asp. asp.−1 asp.−2 asp.−3 asp.−4 1−1 2−2 3−3 4−4

−1.7392 −2.0210 −2.0456 −2.0682 −2.1314 −3.4786 −3.7603 −3.7850 −3.8075 −3.8708 −4.0421 −4.0913 −4.1364 −4.2629

−113.7927 −120.9350 −116.9878 −126.8145 −123.0210 −103.7434 −4.7571 −104.9038 −61.1195

for compounds 1−4 and asphaltene average structure (asp.). For achieving the major quantities of interactions between chemical species, different accommodations were tested, in this way, and the most stable conformation was obtained. After the geometry optimization of the structures, the comparison between total energies, electron density isosurfaces, and atomic charges from Mulliken analysis was used to elucidate the nature of the interactions that take place in the complex formation. With the use of eq 2, the preference of an asphaltene average structure to adsorb with another asphaltene or with a chemical compound molecule can be analyzed. In this way, the aggregation inhibition mechanism is represented. On the other hand, the analysis of the interaction between two chemical compound molecules reveals the feasibility of these compounds to form stable micelles that will improve the efficiency of dispersion of asphaltene aggregates. It can be seen that for all four compounds, the interaction with the asphaltene average structure presents lower energies than the interaction between two asphaltenes; in this way, compounds 1, 3, and 4 present the most stable interactions while compound 2 presents similar energy to the asphaltene dimer. These results are in accord with the possible interactions that can occur between the head of the chemical compound and the asphaltene being strongest for compounds 3 and 4 due to the possibility of formation of hydrogen bonds. For the case of self-aggregation of chemical compounds, the interaction energy between compounds 1 and 3 themselves is similar to their interaction energy with the asphaltene; for the case of compound 4, the energy of self-aggregation is lower but it may still be competitive with the interaction with the asphaltene. Compound 2 has very low interaction with another molecule but it has a relative strong interaction with the asphaltene. The dispersion−inhibition efficiencies for compounds 1 and 3 must be related then to the strong interaction energies among them; this gives us the idea that the stabilization is due to the formation of stable micelles that keep asphaltene aggregates separated from one another. By analyzing the electron density isosurfaces of the complexes (Figure 6), we can observe that the complex formed between compound 4 and the asphaltene average molecule is 1998


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be consulted in the Supporting Information). By comparing the atomic charges of the chemical compounds 1−4 and the average asphaltene structure with the respective atomic charges of their interaction complexes, it was observed that, for the four cases, there exists evidence of π−π stacking between the phenyl group of the chemical compounds and the asphaltene core. In the case of compounds 1 and 2 this is the predominant interaction of the head, while for compounds 3 and 4, there exists evidence of the formation of hydrogen bonds. A coordination interaction performed by the boron in compound 4 is discarded because it turns more positive while to perform a coordination interaction it must gain electron density; however, the two hydroxyl groups can perform effective interactions with the asphaltene by hydrogen bond and dipole−dipole interactions. The experimental activity can be related to these theoretical results; for the case of the asphaltene dispersion−aggregation inhibition activity, to perform an adequate analysis, it is necessary to analyze which concentration of the test corresponds to a one-to-one molar relation with the asphaltene, which is the one modeled. By using the average molecular weight of the chemical compounds and the molecular weight of the asphaltene used for the elucidation of the average structure, molar ratios were obtained for the concentrations in the asphaltene dispersion−aggregation inhibition activity test. Molar ratios of the samples with 0.05 and 0.10 g L−1 of chemical compound are shown in Table 4. Table 4. Molar Ratios of Asphaltene:Chemical Compound in Asphaltene Dispersion−Aggregation Inhibition Activity Test at 0.05 and 0.10 g L−1 of Chemical Compound molar ratio asphaltene:compd compd

0.05 g L‑1

0.10 g L‑1

1 2 3 4

1:0.697 1:0.689 1:0.688 1:0.672

1:1.395 1:1.378 1:1.376 1:1.344

It can be observed that the 1:1 molar ratio is located between these two chemical compound concentrations. The asphaltene dispersion−aggregation inhibition activity between these two concentrations changes between compounds 3 and 4. By the molecular model, compound 4 complex has a lower energy value than compound 3 complex, so the effect is similar to the behavior at 0.05 g L−1. Above this molar ratio, compound 4 has a higher efficiency and it can be assumed that a molar ratio higher than 1:1 is favorable for the dispersion with compound 4. Taking this into account, the molecular model represents very well the system, and the asphaltene dispersion− aggregation inhibition activity can be extrapolated from molecular interactions behavior.

Figure 6. Electron density isosurfaces of (A) asphaltene−1 complex, (B) asphaltene−2 complex, (C) asphaltene−3 complex, and (D) asphaltene−4 complex.

very dense, so it must be very stable; this effective interaction promotes the asphaltene dispersion−inhibition efficiency by the modification of its polarity. Although the interaction energies between compounds 1−3 and the asphaltene are relatively strong, we observe that the complexes are not as dense as with compound 4. Compound 2 has low interaction between two molecules; however, the interaction between a molecule and an asphaltene average structure is relatively strong. As the molecule has to bend to achieve the interaction, it generates disorder by occupying a higher volume. In this way, the molecule promotes the asphaltene breakage or disaggregation leading to smaller aggregates. The disaggregation efficiency will increase as the energy of the system increases, so that is why the viscosity reduction efficiency increases for compound 2 at higher temperatures and shear rates. To confirm the interactions nature, a Mulliken population analysis was performed (the condensed comparative tables can

4. CONCLUSIONS Four aromatic polyisobutylene succinimides were synthesized, evaluated, and molecularly analyzed as viscosity reducers for heavy and extra-heavy asphaltenic crude oils. Aromatic heads can interact with the asphaltene polyaromatic structure by π−π stacking and in compounds 3 and 4 also by hydrogen bond formation and acid−base interaction. A polyisobutylene tail was selected because of its highly branched structure that can generate disorder in the system, helping the breaking of the 1999


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Salle A.C. for the facilities given to obtain the microscope images.

aggregates. Compounds 1, 3, and 4 show good efficiency as asphaltene dispersion−aggregate inhibitors, but apparently this efficiency is not directly related to the asphaltene disaggregation mechanism, where compound 2 has a better efficiency than compound 1. The viscosity reduction seems to be directly related to the disaggregation mechanism, and it has to be noticed that the initial concentration of asphaltenes in the oil mixture is an important parameter to analyze the selection of a chemical agent as flow improver. The effect of the flow improvers decreased as temperature increased, and this is in accordance with the fact that the thermal effect is still governing the viscosity reduction process on heavy crude oils; however, the heat at the mixing zone can be helpful in the diffusion of the chemical product that will show an effect when the oil is cooled down. It has also been observed that the aromatic polyisobutylene succinimide derivatives have an additional viscosity reduction to the one achieved by dilution with the solvent carrier. The asphaltene dispersion−aggregation inhibition and the disaggregation mechanisms were studied by theoretical DFT calculations. We can conclude that the mechanisms of asphaltene dispersion−aggregate inhibition and aggregate breakage act at a molecular scale and can be extrapolated to a macroscopic scale. Finally, we can conclude that, as these compounds present a viscosity reduction effect by modifying the morphology of asphaltene aggregates, they can show a better effect if they are mixed with the crude at the reservoir so that problems such as asphaltene precipitation and pipe clogging are avoided. The study of new chemical products for their use as viscosity reducers and asphaltene stabilizers and how these chemical compounds interact with the surfaces to reduce the friction and improve the flowability of crudes in transport processes continues in our laboratory.

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ASSOCIATED CONTENT

S Supporting Information *

Synthesis procedure of aromatic polyisobutenyl succinimides, spectroscopic characterization, experimental data from the asphaltene dispersion−aggregation inhibition test, and Mulliken atomic charges tables. This material is available free of charge via the Internet at http://pubs.acs.org.

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REFERENCES

AUTHOR INFORMATION

Corresponding Author

*Tel. +52 + 55 91758113, +52 +55 91757548. E-mail: [email protected], [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS T.E.C.-M thanks The National Mexican Council of Science and Technology (CONACYT) and IMP for a Ph.D. scholarship. The authors want to acknowledge the Mexican Institute of Petroleum (IMP), Project Y.00123, for financial support, and Chemical Investigations Center (CIQ) at the Morelos State Autonomous University (UAEM). Also authors want to aknowledge Dr. Edgar Ramirez Jaramillo and Dr. Eduardo Buenrostro Gonzalez for the crude oil samples, Dr. Jose Manuel ́ Martinez Magadán for his help and valuable advice on the optimization of the interaction structures, and Universidad La 2000


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2001


Aromatic Polyisobutylene Succinimides as Viscosity Reducers with

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