Ionic liquids as additives of asphaltene dispersions

Cofinanciado por:
Acronym | LIADA
Project title | Ionic liquids as additives of asphaltene dispersions
Project Code | ALT20-03-0145-FEDER-029458
Main objective | Reforçar a Investigação, o desenvolvimento tecnológico e a inovação

Region of intervention | Alentejo, Lisboa

Beneficiary entity |
  • Universidade de Évora(líder)
  • Associação do Instituto Superior Técnico para a Investigação e o Desenvolvimento (Sigla: IST-ID) (parceiro)
  • FCiências.ID - Associação para a Investigação e desenvolvimento de Ciências(parceiro)

Approval date | 04-10-2018
Start date | 15-12-2018
Date of the conclusion | 14-12-2021
Date of extension | 14-12-2022

Total eligible cost | 231737 €
European Union financial support | FEDER - 191903 €
National/regional public financial support | República Portuguesa - 39834 €
Apoio financeiro atribuído à Universidade de Évora | 220462 €


Asphaltenes, a heavy fraction of crude oil that is soluble in aromatic but insoluble in aliphatic solvents, have a natural tendency to precipitate as a consequence of even slight changes in operating conditions, causing serious problems in oil industry, such as pipeline clogging. The asphaltene nanoaggregates, predicted by most theories, are usually kept in suspension by resins (natural surfactants) present in oil, being displaced by any concentration imbalance in favor of aliphatic hydrocarbons. Carbon dioxide is also known to promote the precipitation of asphaltenes.

In the last years a several substances have been proposed as additives to increase the stability of asphaltene dispersions, being many of them ionic surfactants containing aromatic rings. In some cases, it was observed that the same additive can act as dispersing or precipitating agent (which may also be useful in certain circumstances) depending on its concentration.

The main objective of these project is to explore the possibility of using ionic liquids as additives to stabilize or destabilize asphaltene dispersions in organic solvents that mimic oil. Ionic liquids are structurally similar to ionic surfactants and, by combining cations and anions, it is possible to obtain many ionic liquids designed to meet specific characteristics.

Ionic liquids will be tested as additives to asphaltene suspensions and the best candidates should be chosen. In order to do this in a systematic way, the intermolecular interactions between asphaltenes and a previously selected ionic liquids (according to their structural details) will be investigated by studying pseudo-binary mixtures of both chemicals. Some thermophysical properties (density, viscosity and rheological properties) will be measured for different compositions and temperatures and solution structure and dynamics will also be investigated using NMR and DLS techniques in order to obtain the mobility and dimensions of asphaltene aggregates in different ionic liquids. In addition, molecular dynamics simulations will be also carried out in order to predict the thermophysical properties and to obtain some molecular insights on these systems.

Then, aggregation studies of asphaltenes on simple mixtures of aromatic and aliphatic solvents (in some cases including carbon monoxide) will be done by molecular dynamics simulation in order to screen the families of ionic liquids in terms of their tendency to stabilize dispersions or promote precipitation.

Some selected ionic liquids obtained from the previous screening procedure will be used in experimental precipitation tests in simple solvents and also used as components in vapour-liquid and vapour-liquid-solid equilibria measurements involving asphaltenes and synthetic mixtures that mimic oil.

The body of results that is expected to be obtained will allow the proposal of some ionic liquids that can be used in real conditions to prevent/promote precipitation in the any step of oil processing.

Goals, activities and expected/achieved results

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.


Espera-se com estes resultados:

Artigos em revistas cientíicas de circulação internacional com arbitragem.

Comunicações em congressos internacionais.


Teste de aditivos escolhidos em amostras reais em contexto industrial.