Gaspar González
Petrobras
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Featured researches published by Gaspar González.
Journal of Petroleum Science and Engineering | 2001
André L. C. Machado; Elizabete F. Lucas; Gaspar González
Abstract Several techniques have been used to minimize the problems caused by the wax deposition, and the continuous addition of polymeric inhibitors is considered an attractive technological alternative. The addition of copolymers like polyacrylates, polymethacrylates or poly(ethylene-co-vinyl acetate) (EVA) permit to inhibit the deposition phenomenon; nonetheless, this effect is specific, i.e. similar copolymers present different performance depending on their physical–chemical properties in solution. In this work, the influence of the EVA vinyl acetate content on the viscosity and the pour point of a Brazilian crude oil were evaluated. A correlation between both results was also obtained. The phase behavior and the solubility parameter of EVA copolymers, with different vinyl acetate contents, were investigated in various solvents together with an evaluation of the efficiency of these copolymers as pour point depressants for two different samples of crude oil. EVA copolymers containing 20, 30, 40 and 80 wt.% of vinyl acetate were used and tests with the crude oil were carried out using 50, 500, 1000 and 5000 ppm of EVA as additive. The results obtained from viscosity measurements showed that only below the temperature at which wax crystals start forming did the copolymer exhibit a strong influence in the reduction of oil viscosity, at an optimum concentration. The pour point results revealed EVA 30 to be the most efficient. The results obtained from both experiments showed that the viscosity and the pour point behaviors do not show good correlation. Not only the solubility parameter and the vinyl acetate content, but also the molecular weight and polydispersity have an important influence on both phase behavior and pour point depression. Furthermore, it was confirmed that the additive must present a reduced solubility at a temperature close to the crude oil cloud point. This, however, is not the only factor that determines the efficiency of the additive as paraffin/wax deposition inhibitor.
Colloids and Surfaces | 1991
Gaspar González; Antonieta Middea
Abstract The dispersion of asphaltene in heptane by different oil soluble amphiphiles was investigated. Alkyl phenols show good peptizing properties and partially lose their capacity when oxyethylenic groups are incorporated into the molecule. Primary aliphatic amines also show some ability to disperse asphaltene, but long chain aliphatic alcohols and alkyl benzenes are rather inefficient. Asphaltene solutions in toluene containing alkyl phenols are less sensitive to precipitation by the addition of low molecular weight alkanes. The asphaltene adsorption onto quartz was also reduced by the addition of amphiphiles.
Colloids and Surfaces | 1991
Gaspar González; Maria Bárbara C. Moreira
Abstract Studies on the adsorption of asphaltenes, extracted from shale oil and dissolved in toluene on various minerals, were carried out. Langmuir-type isotherms were obtained showing a maximum adsorption density of 1–2 mg m −2 for most minerals. The adsorption process produced marked changes in the wettability of the solid. The contact angles measured at the mineral-water-toluene solution interface for asphaltene-covered surfaces at neutral pH were 102° for quartz, 89° for calcite, 72° for magnesite and 110° for mica, whereas the corresponding values for the bare minerals were 32 ± 2°. Confirmatory results were obtained using immersion tests for powdered mineral samples. The contact angle depends on the aqueous phase, going through a maximum between pH 3 and pH 8; similar results were obtained for the interfacial tension between water and a solution of asphaltene in toluene. For low asphaltene concentrations the contact angles reverted to lower values on exposure of the mineral with adsorbed asphaltenes to the pure solvent. However, this inversion was not possible for higher asphaltene concentrations. Similar behavior was observed in previous work for the displacement of asphaltenes from the mineral-solution interface by non-ionic surfactants. These results were ascribed to lateral interactions that make the adsorption process irreversible for high sarface coverage.
Journal of Dispersion Science and Technology | 1987
Gaspar González; Antonieta Middea
ABSTRACT The adsorption of asphaltenes and resins from toluene solutions onto quartz and feldspar and the effect of this process on the properties of the mineral-aqueous solution interface have been investigated. Asphaltenes were adsorbed to a greater extent than resins, and the adsorption of mixtures was at least equivalente to the weighted average of the adsorption of both components separately. The electrophoretic mobility of quartz or feldspar was not modified by the adsorption of asphaltenes or resins, indicating that the sites responsible for the surface charge of the minerals were unaffected by the presence of the adsorved organic species. The adsorption turned the minerals partially hydrophobic. This effect is more important for asphaltene covered particles which do not immerse in aqueous electrolyte solutions, indicating a contact angle larger than 90a immersion become spontaneous in liquid mixtures (methanol-water, ethanol-water), presenting a surface tension lower than 35 mNm-1. Ethoxylated and...
Spe Production & Facilities | 1993
Gaspar González; Ana Maria Travalloni-Louvisse
Asphaltenes show moderate capacity to reduce oil/water interfacial tension (IFT) and/or stabilize emulsions. However, in the presence of other surfactants and fine particles presenting intermediate wettability, these compounds enhance emulsion formation and stability. At the solid/solution interface, asphaltenes adsorb up to a saturation value of 2 to 3 mg/g and modify the mineral wettability. At the oil/solution interface, asphaltenes adsorb up to a saturation value of 2 to 3 mg/g and modify the mineral wettability. At the oil/gas interface, the asphaltic fractions adsorb as single molecules or as liquid crystalline phases, causing foaming problems.
Colloids and Surfaces A: Physicochemical and Engineering Aspects | 1999
R.C.G. Oliveira; Gaspar González; J.F. Oliveira
Abstract The removal of emulsified residual oil from water is an important issue due to the increasing concern with the environment. In the present paper various surface chemistry aspects of dissolved gas flotation were studied aiming at a better understanding of the mechanisms of the process. These studies included surface and interfacial tension measurements of a model system composed of n-dodecane in the presence and absence of nonyl-phenol. Critical micelle concentration and spreading coefficients determinations were undertaken at different NaCl concentrations. The spreading coefficient proved to be a critical parameter in oil droplets flotation. After bubble–drop contact and rupture of the water film, oil drops have a tendency to spread over the bubble surfaces. The spreading coefficient increased with increasing salt concentration. An experimental setup was designed to measure the induction contact time between single n-dodecane droplets and air bubbles. Induction time decreased with increasing salt concentration. In the presence of the nonyl-phenol aqueous solution, induction time decreased with time of stabilization. On the other hand, induction time increased with time of stabilization when nonyl-phenol was added to the organic phase. The mechanisms involved are discussed and some results obtained in a dissolved air flotation batch unit in which bubbles size was measured and controlled are also presented.
Colloids and Surfaces | 1988
Gaspar González; Antonieta Middea
Abstract The adsorption of three different samples of asphaltenes and resins onto calcite was studied. For all the samples the adsorption of asphaltenes was greater than that of resins, the plateaus being between 2 and 3 mg g −1 for asphaltenes and between 0.5 and 0.6 mg g −1 for resins. The adsorption process produced important changes in the wettability of calcite. The equilibrium contact angle measured at the calcite—water—toluene interface was between 80 and 95° for asphaltenes and between 60 and 85° for the resins fraction. These figures are lower than the corresponding values obtained for quartz. This result explains the presence of quartziferous particles in a greater amount than calcareous material in asphaltic sludges. The adsorbed asphaltic fractions did not modify to a great extent the electrophoretic mobility of calcite particles, in agreement with previous results obtained for quartz and feldspar.
Journal of Dispersion Science and Technology | 2007
Geiza E. Oliveira; Claudia R. E. Mansur; Elizabete F. Lucas; Gaspar González; Wladmir F. Souza
The influence of asphaltenes and naphthenic acids on wax appearance temperature (WAT), wax crystals morphology, and pour point was estimated for solutions of a commercial paraffin sample dissolved in a solvents mixture. In addition, the performance of copolymers obtained by modification of ethylene‐vinyl acetate copolymers as organic deposition inhibitors (ODI) also was studied. Asphaltenes reduced the pour point and this effect increased with the increase in the asphaltenes concentration, indicating that asphaltenes interact with the paraffins to form particles with a different interaction profile. The observation of the wax crystals using optical microscopy revealed that in the absence of additives the solid wax particles form a homogeneous mass, evenly distributed throughout the whole sample having a plane lamellar structure which favor aggregation. When asphaltenes were incorporated, the particles were smaller and less well defined. At higher asphaltenes concentrations, dark particles whose surface resembled asphaltenes also were observed. Naphthenic acids caused a small increase in the pour point and when both fractions, asphaltenes and naphthenic acids, were added together, the asphaltenes seem to have their pour point reduction effect depressed. The ODI presented some efficiency as pour point reducers but, in the presence of asphaltenes, this efficiency was largely enhanced suggesting that beside the alteration of the particles an efficient dispersion mechanism is also necessary to inhibit the aggregation of the wax particles.
Journal of Applied Polymer Science | 1997
Claudia R. E. Mansur; Clara Marize F. Oliveira; Gaspar González; Elizabete F. Lucas
Phase behavior of aqueous systems containing block copolymers of poly(ethylene oxide (PEO) and poly(propylene oxide) (PPO) was evaluated by building up temperature-concentration phase diagrams. We have studied bifunctional triblock copolymers (HO-PEO-PPO-PEO-OH) and monofunctional diblock copolymers (R-PEO-PPO-OH and R-PPO-PEO-OH, where R length is linear C 4 and C 12-14 ). The cloud points of the polymer solutions depended on EO/PO ratio, polarity, R length and position of the hydrophilic and hydrophobic segments along the molecule. Such factors influence on the solutions behavior was also analyzed in terms of critical micelle concentration (CMC), which was obtained from surface tension vs. concentration plots. Salts (NaCl and KCl) added into the polymer solutions change the solvent polarity decreasing the cloud points. On the other hand, the cloud points of the polymer solutions increased as a hydrotrope (sodium p-toluenesulfonate) was added.
Colloids and Surfaces A: Physicochemical and Engineering Aspects | 1999
Claudia R. E. Mansur; Luciana S. Spinelli; Elizabete F. Lucas; Gaspar González
Abstract The aqueous solution behavior of diblock poly(ethylene oxide)–poly(propylene oxide) (PEO–PPO) copolymers coupled with hydrocarbon groups was studied in the presence of the hydrotropic agent sodium p-toluenesulfonate (NaPTS). The change in phase of the aqueous systems was evaluated by building up temperature–concentration phase diagrams. The critical micelle concentrations (CMC) of the copolymers and the aggregation points of NaPTS and NaPTS/copolymer mixtures were obtained by surface tension measurements, viscometry data and dye solubilization. The copolymers and NaPTS adsorb and reduce the surface tension of the solution until the surface becomes saturated: the CMC values are related to the solubility of the copolymers. Solutions containing NaPTS/copolymer mixtures exhibit the opposite behavior: at constant copolymer concentrations and with increasing NaPTS concentration, the surface tension remains constant until the aggregates of NaPTS start to form. Above this concentration, the surface tension increases. The surface tension and the aggregation points of the NaPTS solutions are dependent on the structure of the copolymer. The influence of the length of the hydrocarbon groups and the PPO position segment in the structure of the copolymers were also studied. From viscometric data, a pronounced increase in solution viscosity was observed as aggregates began to form. The results obtained from dye solubilization are in good agreement with the surface tension and viscometric measurements.
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Marcia Cristina Khalil de Oliveira
Federal University of Rio de Janeiro
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