Ionic liquids as additives of asphaltene dispersions

The precipitation of asphaltenes constitutes nowadays a serious problem to oil industry since this phenomenon can lead to blocking pipelines, considerably diminishing the oil processing and the production of many oil transformation products. The tendency of such a phenomenon to occur depends on the operation conditions and on the oil composition, being carbon dioxide (naturally occurring component in oil wells or added in extraction process) a known promoter of asphaltene deposition. In particular, it is known that subtle changes in operation conditions (composition, temperature, pressure) may produce asphaltene precipitation.

Several additives to crude oil and oil products have been proposed as asphaltene precipitation inhibitors, most of them surfactants, hoping to play the same role as natural resins from crude oil which are thought to stabilize oil suspensions.

The key idea of this project is to explore the possibility of using room temperature ionic liquids to stabilize dispersions of asphaltenes in relevant media and, from a deeper understanding of the interactions between asphaltenes and ionic liquid surfactants, to screen the possible additives to use, as a function of asphaltene composition and operation conditions. Since it is known that some additives at specific ranges of composition tend to show the opposite effect (inducing precipitation), the possibility of using this additives to promote precipitation in order to separate asphaltenes from oil (and their valorization) will also be explored.

Ionic liquids are low melting organic salts. They can be synthetized with a large diversity of cations and anions, custom tailored at the molecular level to meet specific purposes. Due to their extremely low volatility, ionic liquids are often considered green solvents. Additionally, ionic liquids are non flammable, display high thermal stability, wide liquid range and a wide electrochemical window.

At the molecular level, ionic liquids are very similar to common ionic surfactants, with the advantage of being in the liquid state. It could thus be expected that ionic liquids interact with asphaltene cores, enhancing the stability of dispersions.

This project proposes a systematic approach to the subject, focusing on the thermodynamic and thermophysical properties of the systems of interest. The ultimate aim is to understand, and thus optimize, the mechanism of stabilization (or destabilization) of asphaltenes dispersions with ionic liquids in different media, and finally to propose a certain number of ionic liquids as new additives to asphaltene dispersions.

The stability of asphaltene dispersions implies compatibility between asphaltene particles and the surrounding media. The role of the ionic liquid, while located at the interface between alphaltenes and the solvent, is to promote their compatibility by simultaneously interacting with the asphaltene core, through Coulomb forces, hydrogen bonding, p-p stacking, etc and with the solvent, through dispersive forces.

In this context, interactions of ionic liquids with the asphaltene particles play an obvious important role. However, the affinity of side chains with the solvent is not, by all means, of lesser importance. Moreover, the composition of the solvent can change considerably and media with very high CO2 content are not uncommon. Ionic liquids with side chains compatible with CO2 should thus be chosen and those with perfluorinated chains are particularly well suited for this purpose.

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Artigos em revistas cientíicas de circulação internacional com arbitragem.

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