Asphaltenes in crude oil

Asphaltenes - Problems and Solutions in E P of Brazilian Crude Oils 

Erika Chrisman, Viviane Lima and Priscila Menechini Federal University of Rio de Janeiro/DOPOLAB 

The history of oil in Brazil began in 1858, when the Marquis of Olinda signed Decree No. 2266 granting Barros Pimentel the right to extract mineral asphalt for the manufacture of kerosene, on land situated on the banks of the Rio Marau in the province of Bahia. But who really came to be known as the discoverer of oil in Brazil was Monteiro Lobato that on January 21, 1939, already under the jurisdiction of the newly created Department of National Production, began drilling the well DNPM-163 in Bahia. 

Only in 1953 began the research of Brazilian cal by the government of Vargas, which established the state oil monopoly, with the creation of Petrobras. 

Petrobras - Petroleo Brasileiro 5/ A was founded on October 3,1953 and headquartered in Rio de Janeiro, now operates in 28 countries in the energy sector, primarily in the areas of exploration, production, refining, marketing and transportation of oil and derivatives in Brazil and abroad. Its current motto is An integrated energy company that works with social and environmental responsibility (http //pt.wikipedia.org/wiki/Petrobras). 

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Other techniques such as X-ray diffusion or small angle neutron diffusion are also used in attempts to describe the size and form of asphaltenes in crude oil. It is generally believed that asphaltenes have the approximate form of very flat ellipsoids whose thicknesses are on the order of one nanometer and diameters of several dozen nanometers. 

Certain alkyl-substituted phenol-formaldehyde resins can act as dispersants for asphalts and asphaltenes in crude oils [1681]. The dispersants help keep asphalt and asphaltenes in dispersion and inhibit fouling, precipitation, and buildup in the equipment. 

Asphaltenes can exist in various structural forms such as peri-condensed and kati-condensed rings. Upon heating, peri-condensed asphaltenes in crude oil have been shown to rearrange into kati-condensed asphaltenes. 

Speight, J.G. Asphaltenes in Crude Oil and Bitumen Structure and Dispersion in Suspensions, Fundamentals and Applications in the Petroleum Industry, Schramm, L.L. (Ed.), American Chemical Society Washington, 1996, pp. 377 101. 

In the next two chapters, the reader will be exposed to the main problems that arise for the crude oil industry due to the presence of asphaltenes in crude oil. The reader will also be exposed to the latest results of investigations of various possibilities for conversion to useful products of asphaltenes and heavy oil. 

The presence of asphaltene in crude oil causes problems for oil treatment as... 

Thanh, N. X., Hsieh, M. Philp, R. P. 1999. Waxes and asphaltenes in crude oils. Organic Geochemistry, 30, 119-132. 

McLean and coworkers [19,56] have investigated the effects of crude oil solvency and resin-asphaltene interactions on the stability of water-in-crude oil emulsions. They showed that there were three main factors that control the solubility of asphaltenes in crude oil, their tendency to aggregate, and their tendency to adsorb at oil-water interfaces. These are... 

It is well known that resins are good dispersing agents for asphaltenes in crude oil. From previous results, the resin films are not strongly influenced by bulk concentration or the nature of the spreading solvent. Hence, it is of major interest to study mixed films of resins and asphaltenes. Figure 5 shows the surfaee eoncentration of asphaltene/resin mixtures necessary to aehieve a surface pressure equal to 10 mN/m, when both solvent aromaticity and bulk concentration of resins are varied with the bulk concentration of asphaltenes is fixed (4mg/ml). 

The solubility of asphaltenes is highly dependent on the medium in which they are placed (81). The presence of dissolved asphaltenes in crude oil is mediated by a combination of crude aromaticity and petroleum resins that act to solvate asphaltene aggregates. Adding an excess of aliphatic solvent, namely n-hep-tane, sufficiently reduces the solubility of asphaltenes in crude oil and causes precipitation. To perform subsequent film experiments these precipitated asphaltenes were then redissolved in toluene. As n-heptane was added to the asphaltene—toluene solutions. 

Asphaltenes in crude oil are large, bulky molecules which behave like polymer molecules. Thus, liquid-liquid polymer solution theories are used to... 

Because the asphalt system is not a true solution, it can be fractionated into saturates, aromatics, resins, and asphaltenes by the solvent fraction method, SARA method, or TLC method. The polarity of these four fractions is increased in the order of saturates, aromatics, resins, asphaltenes. In crude oil, asphaltene micelles are present as discrete or dispersed particles in the oily phase. Although the asphaltenes themselves are insoluble in gas-oil (saturates and aromatics), they can exist as fine or coarse dispersions, depending on the resin content. The resins are part of the oily medium but have a polarity higher than gas-oil. This property enables the molecules to be easily adsorbed onto the asphaltene micelles and to act as a peptizing agent of the colloid stabilizer by charge neutralization. 

The state of asphaltenes in crude oil also has an effect on its stabilizing properties of emulsions. The asphaltenes will stabilize emulsions when they are present in colloidal form There is strong evidence that its properties are significantly increased when stabilizers are precipitated in the oil. 

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