Phase transition and viscosity behavior of emulsified systems were studied after modifying their physicochemical formulation. Effects of concentration and nature of salts and n-alcohols, and water/oil relation on the rheological properties of emulsions were also studied. Pre-equilibrated systems were emulsified according to an agitation procedure, and the viscosity (cP) was measured at different shear rates ranging from 1 to 300 s-1. The phase behavior, as well as the emulsion type based on electrolytic conductivity, was observed. Several interpretations of the flow and viscosity curves of emulsions were made through the estimation of rheological parameters such as consistency index "k" and behavior index "n".

The use of fatty acids (FAs) as amphiphiles is very important because they have a behaving similar to surfactants. The formulation for the preferential partition of these species was studied by varying the amount of salt at constant acid concentration. As the salt concentration increases, a Winsor I→III→II transition is observed for all the systems studied. Furthermore, the electrolyte concentration required to obtain the optimum formulation varies inversely with the chain length of the acid. The partition coefficient of the surfactant allows one to obtain thermodynamic information on the acid transfer process between the phases of the system.

En el presente trabajo se estudiaron las propiedades tensoactivas de las fracciones obtenidas mediante degradación oxidativa asistida por microondas con peróxido de hidrógeno de dos ligninas de pino (LAA y LKM). Las reacciones fueron llevadas a cabo en recipientes cerrados, empleando diferentes cantidades de agente oxidante, en un horno microondas doméstico. Las reacciones se completaron rápidamente, generando agua como subproducto. Los productos de oxidación fueron caracterizados por espectroscopia UV-Vis y FTIR. Al compararlos con las muestras originales de lignina se observó una disminución de la absorción cerca de los 280 nm debido a la oxidación de los anillos aromáticos. En el análisis por FTIR se observó el aumento de las señales correspondientes a los grupos C=O entre 1.700-1.720 cm-1 y entre 1.650-1.700 cm-1 atribuidas a la oxidación de las cadenas laterales y de los anillos aromáticos, respectivamente. Esto último se evidenció por la disminución de la señal C=C aromática, alrededor de los 1.600 cm-1. Se comprobó la eficiencia y versatilidad de la radiación microondas para promover este tipo de reacciones. Las ligninas oxidadas mostraron un aumento de la tensión superficial debido a la aparición de nuevos grupos polares.

In this work the fractions obtained by microwave-assisted oxidative degradation with hydrogen peroxide of two pine lignins (LAA y LKM) and its tensoactive properties were studied. The reactions were carried out using different quantities of the oxidant agent in a domestic microwave oven in closed reactors. The reaction was completed quickly with the generation of water as by-product. The oxidation products were characterized by UV and FTIR spectroscopy. When comparing them with the original lignin samples in UV analysis, the absorption decreased near the 280nmdue to the oxidation of the aromatic rings. In the analysis by FTIR the signals corresponding to the groups C=O increased among 1,700-1,720 cm-1 and 1,650-1,700 cm-1 attributed to the oxidation of the lateral chains and aromatic rings, respectively. This results were evidenced because of the aromatic signal C=C around the 1,600 cm-1 decreased. It was proven the efficiency and versatility of the radiation microwaves to carry out this type of reactions. The surface tension of the oxidized lignin increased due the new hydrophilic groups.

Las emulsiones de crudo en agua se han utilizado para producir y transportar hidrocarburos pesados. En estudios anteriores se determinó que las emulsiones de crudo en agua preparadas con mezclas de surfactantes no-iónicos y aniónicos son más estables y menos viscosas que las emulsiones preparadas con un único surfactante, y que adicionando aminas de cadena corta se logra incrementar la estabilidad de dichas emulsiones. En este artículo se discute el efecto de aminas alifáticas de cadena corta en la estabilidad y las propiedades reológicas de emulsiones de crudo pesado en agua, preparadas a una relación crudo/agua 70/30. Se utilizaron surfactantes no-iónicos polietoxilados, tanto individualmente como mezclados con un surfactante aniónico del tipo aril benceno sulfonato. Se emplearon como co-surfactantes aminas alifáticas de 2, 4 y 6 átomos de carbono, tanto de cadena lineal como ramificada. Los resultados mostraron que las aminas primarias de cadena lineal producen emulsiones más estables y con mayor viscosidad que las emulsiones preparadas con aminas secundarias o terciarias de igual número de átomos de carbono. Se concluyó que las aminas alifáticas cortas son excelentes co-surfactantes, ya que estabilizan las emulsiones formadas en el sistema surfactante-agua-crudo.

The crude oil in water emulsions have been used to produce and to transport heavy hydrocarbons. More stability and less viscosity than the emulsions prepared with an only surfactant was obtained for the crude oil in water emulsions prepared with non-ionic and anionic surfactant mixtures, in previous studies. The stability of these emulsions could be increased, adding short chain amines. In this work, the effect of aliphatic short chain amines in the stability and the rheological properties of heavy crude oil in water emulsions, prepared at crude oil/water relationship of 70/30, is discussed. Polyethoxylated non-ionic surfactants were used, individually or in a mixture with an anionic surfactant of aryl benzene sulfonate type. Aliphatic short chain amines of 2, 4 and 6 atoms of carbon were used as co-surfactants, so much of lineal chain and ramified chain. The results showed that the primary amines of lineal chain produce more stable emulsions and with more viscosity that the emulsions prepared with secondary or tertiary amines of the same number of atoms of carbon. It was concluded that aliphatic short chain amines are excellent co-surfactants, because they stabilize micelles formed inside the system surfactant-water-crude oil.

En el presente trabajo se evaluaron formulaciones para emulsionar crudo pesado en agua, a una relación crudo/agua 70/30. Se utilizaron surfactantes no-iónicos y aniónicos, mientras que aminas de cadena corta se emplearon como co-surfactantes. Se evaluaron la estabilidad, la viscosidad, la conductividad, el tamaño promedio de gota y la distribución de tamaño promedio de gota. Se obtuvieron emulsiones estables para sistemas simples y múltiples, cuyas viscosidades son considerablemente menores a la viscosidad original del crudo, todas de fase externa agua y con una amplia zona de inversión. El tamaño mínimo promedio de gota obtenido fue de 23 mm, con distribuciones polidispersas, tanto unimodales como bimodales. Se concluyó que las mezclas de surfactantes no-iónicos y aniónicos originan una sinergia positiva incrementando la estabilidad de las emulsiones de crudo en agua, y que las aminas de cadena corta son excelentes co-surfactantes, ya que estabilizan las micelas formadas dentro del sistema surfactante-agua-crudo

In the present work, formulations to emulsify heavy crude oil in water, at crude oil/water relationship of 70/30, were evaluated. Non-ionic and anionic surfactants were used with amines of short chain as co-surfactants. Stability, viscosity, conductivity, drop size and size distribution, were evaluated. Stable emulsions were obtained with simple and multiple systems which smaller viscosities than the original crude oil, all them with external phases of water and “extended inversion zone”. The minimum drop size obtained was of 23 µm, with polydisperses distributions, unimodals and bimodals. It was concluded that non-ionic and anionic surfactants mixtures originate a positive synergy, increasing the stability of the crude oil emulsions, and as well as that short chain amines are excellent co-surfactants, because they stabilize micelles formed inside the surfactant-water-crude oil system