Asphaltene deposition is a well-known problem in the petroleum industry. Nevertheless, there seems to be a lack of information on the processes involved in asphaltene association and its relationship to asphaltene solubility under certain conditions. Molecular mechanics and molecular dynamics have had an important role in the investigation of these phenomena. To better understand the role of solvents in fractionating asphaltenes extracted from vacuum residues and evaluate their tendency to dissociate under different conditions, we modeled the effect of toluene, n-butane, isobutane, and n-heptane on an aggregate formed by two asphaltene molecules that would have a tendency to associate (not average structures commonly used in similar studies). Molecular dynamics simulations were performed on an asphaltene dimer after minimizing the conformation of each molecule and verifying the most stable position for docking. They reveal the extent to which these solvents are able to separate the aggregate at different temperatures after a given period of time. As expected, toluene is the most effective and n-heptane affects the aggregate the least, with n-butane and isobutane falling between these two bounds.
Asphaltenes represent a solubility class of petroleum constituents that has been associated with a number of problems that arise from the use of heavier crude oils. As they are defined by their solubility and not their chemical structure, there are often certain difficulties in distinguishing them from other solubility fractions. In a widely adopted separation procedure, saturates generally consist of naphthenes and paraffins while aromatics, resins, and asphaltenes are often quite similar polynuclear aromatic species which may vary in the number of heteroatoms and sizes of ring systems and side-chains that are present. In our attempts to characterize asphaltenes extracted from vacuum residues, we found that the procedures employed for separating asphaltenes in a certain sample have a significant effect on the analytical data that is generated from it. We have thus investigated the influence of different variables on vacuum residues obtained from two Brazilian and one Venezuelan crude and suggest that the most important factors are: the proportion of heptane to sample, treatment by ultra-sound and recovery of asphaltenes in residues by toluene. Combinations of these variables can be employed to hinder aggregation and afford a better separation of asphaltenes and resins. The analytical techniques that were used to confirm this are: NMR ( 1 H and 13 C), gel permeation chromatography (GPC), infrared spectroscopy (IR), and elemental analysis. Information on the types of aromatic ring substitution patterns and terminal methyl groups may be obtained from spectroscopic techniques particularly from NMR.
Resumo: O uso de inibidores de corrosão para o controle do processo corrosivo de materiais metálicos em meios agressivos consiste em uma prática tradicional da indústria petrolífera. Os compostos orgânicos estão sendo estudados para avaliar o seu comportamento frente ao potencial de inibição. Estudos revelam que certos compostos com presença de heteroatomos de N, S e O apresentaram eficiência de inibição significativa. Entretanto, a maioria destes compostos apresenta toxicidade elevada quanto à tolerância máxima de seres vivos. Este trabalho tem como objetivo a aplicação de análises estatísticas (analise fatorial -MANOVA) para avaliar as condições operacionais envolvidas em processos de acidificação de poços de petróleo. Os resultados experimentais revelam que a metodologia estatística proposta poderia ser utilizada para indicar novas formulações de inibidores comerciais a partir compostos orgânicos que apresentassem baixa toxicidade e alta eficiência de inibição para vários metais e ligas metálicas em meios agressivos.Palavras-chave: corrosão, inibidores de corrosão, planejamento de experimentos, toxicidade.Abstract: The use of inhibitors for mild steels corrosion control which are in contact with aggressive environment is an accepted practice in acid treatment of oil-wells. Lots of organic compounds are being studied to investigate their corrosion inhibition potential. Studies reveal that organic compounds with N, S and O showed significant inhibition efficiency. But most of these compounds are toxic to living beings. This article gives a factorial analysis to evaluate the optimum conditions of operational parameters involved in oil-well acidizing processes. The experimental results showed that the proposed statistical methodology could be used to indicate corrosion inhibitors based on organic compounds which have low toxicity and high inhibition efficiency for various metal and alloys in aggressive media.
The waxes in petroleum can precipitate and form unwanted gels and deposition when exposed to low temperatures. The idea of this chapter is to approach methods of quantification and physicochemical and morphological characterization of waxes and how this information can help in understanding this deposition. Information such as the quantity of waxes and the chemical structures in the oil is fundamental to predict the possible deposition and its ability to aggregate with other crystals. For example, the knowledge about the wax morphology may contribute to explain the nucleation and growth of the deposits. The polarized light microscopy, the most common technique to visualize wax crystals, and the brightfield microscopy, the most simple technique, able to show crystal details that have not been seen on the polarized light, was used.
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