The electrophoretic mobility of asphaltene particles formed by precipitation induced by the addition of n-heptane to asphaltene solutions in toluene was measured in water and in nonpolar media. Dispersed in water, the particles presented a negative electrophoretic mobility, whereas in toluene their mobility was positive and around 2.0 × 10 -9 m 2 /V s. When resins were present in the precipitating medium, a coprecipitation of these fractions occurred, indicating an adsorption or binding process of the resins on the nascent asphaltene particles. This interaction, however, did not significantly change the electrophoretic mobility of the asphaltene particles. In contrast with commercial dispersants, resins fail to stabilize asphaltene dispersions. This result indicate that the descriptions representing asphaltenes as a solid phase intrinsically insoluble in hydrocarbon media dispersed by adsorbed resins molecules does not accurately represent the structure of these fractions

Cholesterol reduction together with the fractionation of triglycerides in butter oil was obtained using a combined supercritical CO 2 extraction/alumina adsorption process in a high-pressure apparatus that allows the independent control of temperature and pressure. Cholesterol levels in butter oil fractions extracted at 40°C and 27.6 MPa were reduced from 2.5 to 0.1 mg g Ϫ1 of oil. Butter oil was also fractionated into low-, intermediate-or high-molecular-weight triglycerides. This single-stage combined process is a clear indication of the important technological possibilities with a more efficient multistage fractionation followed by the subsequent blending and formation of desired milk fat products. A comparison of solubility data of pure cholesterol in CO 2 with those for cholesterol contained in butter oil revealed the co-solvency effects of triglycerides on the solvation of cholesterol.

The solubility of asphaltenes in heptane/toluene mixtures was studied at several temperatures. A significant increment in asphaltene solubility was observed when the temperature increases from 0 • C to 20 • C and a moderate increase when the temperature rose from 20 • C to 50 • C. These results indicate that asphaltenes behave as a higher consulate temperature system, similar to nonpolar waxes. Examined by photon correlation spectroscopy, diameters from the particles formed a range between 125 and 400 nm, depending on the amount of non-solvent (n-heptane) used for the precipitation process and the initial concentration of asphaltenes. The particles presented a small positive surface potential that was not altered by the addition of resins. 35

Literature data on the influence of magnetic fields on organic deposition process are most oriented to charged species, e.g., calcium carbonate scale. It has also been claimed that the use of magnetic tools can mitigate paraffin deposition in flow lines. If this technique can be applied to subsea flowlines the benefits are potentially high. However, magnetic tool manufacturers do not provide the necessary level of information to make the customer feel comfortable to rely on such devices. Therefore, a research project has been established to shed some light to this yet controversial subject. The paraffin crystallization process under the influence of magnetic fields and paraffin inhibitors (PIs) has been investigated with the aid of Microscopy. The objective of this study was three-folded - to provide a laboratory evidence to recommend - or not - the use of magnetic tool in the field, - to verify the Microscopy usefulness to study non-isotropic paraffin crystallization process and, - to provide an additional tool to help in selecting PIs. To our best knowledge the technical contributions of this study are- to confirm that magnetic field do alter paraffin crystallization process, - to establish a relationship between PIs and the paraffin crystallization process and, - the development of experimental analytical procedures to investigate paraffin deposition-related processes. Introduction Paraffin deposition is a well-known phenomenon that plagues the oil industry all over the world. As a rule paraffin problems can been solved in onshore fields with inexpensive physical and chemical methods. However, as the oil industry is continually moving to deep water scenarios where paraffin deposition takes place in difficult-to-reach subsea flow lines, manifolds and wet Xmas trees, no inexpensive solutions are known. Conversely, operators are concerned to paraffin deposition problems in deepwater production facilities for they are costly, time-consuming and means a serious menace to the economical feasibility of their enterprises. To cope with operational problems associated to organic deposition in deep waters, Petrobras has been funding an integrated research program - the so-called Petrobras Flow Assurance Program (PROCAP) - aimed at forecasting organic deposition and preventing and/or solving the problem in offshore wells. A set of preventive and remedial solutions were either in-house- or jointly-developed. The major products that arose from this research effort are briefly described as follows: Pigging A jointly industrial project on pipeline pigging simulation was launched by Petrobras in 1996. More than one hundred successful pigging operations have been conducted in subsea flow lines in Campos Basin so far. Nitrogen Generating System (SGN) The SGN method comprises the controlled reaction between two nitrogen-containing chemicals which is capable of generating a large amount of nitrogen gas and heat. The method has been successfully used in more than one hundred operations in Campos Basin area. Paraffin Inhibitors The use of paraffin inhibitor (PI) is another approach to solve paraffin deposition problems in offshore fields. The technology which also includes the correct application of these chemicals in the field has been used in a long-term test in the Albacora field, Campos Basin. On-going research on this subject has been oriented toward finding more cost-effective PI's and understanding how these chemicals prevent paraffin crystals from growing. Magnetic devices A study to investigate the potential of the so-called magnetic fluid conditioners (MFCs) to inhibit paraffin deposition is being carried out at Petrobras Research Center.

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