Traditional separation and extraction of oil and bitumen from soil, sand, or other forms of mineral matter is a difficult and expensive process. The warm water methods presently used to extract bitumen from oil sands require large amounts of energy and result in the generation of significant quantities of waste process water that is toxic to aquatic life. Extrakt Process Solutions has developed an environmentally friendly and energy efficient process for separating bitumen, oil, or other hydrocarbons from sand, soil, or other particulate matter through the use of ionic liquids (ILs) and diluents. The separation occurs at ambient temperatures and does not result in the generation of waste process water.
WHAT ARE IONIC LIQUIDS?
Ionic liquids (ILs) are materials that are made up of ions, like common table salt (Na+Cl–), except that they are liquids below 100˚C. Because of their ionic nature they have unusual properties. In the Extrakt process they interact strongly with mineral surfaces and promote oil or bitumen separation.
Some water is used to remove IL from extracted sand, but both water and IL are easily separated and recycled through a closed system. For oil sands extractions, there is no need for tailings ponds. Clean minerals and oil are obtained from various types of sludge, remediating a significant environmental problem while providing materials that can be recycled and have economic value. The process is simple, as it involves conventional mixing and physical separation steps utilizing “off-the-shelf” equipment.
HOW DOES THE TECHNOLOGY WORK?
Because of their ionic nature, ILs have an affinity for minerals surfaces, which also have a charge. As a result, in the presence of an IL the energy of adhesion between bitumen and oil is close to an order of magnitude smaller than in water, facilitating separation. Using water instead of an IL results in a poor separation and emulsified mineral particles in the separated oil, as illustrated below for a separation of Alberta oil sands using an IL and a hydrocarbon solvent as a diluent.
Note that in this application, ILs are used as a separating fluid, not as a solvent. They are immiscible with hydrocarbons and because of density differences a separation into three layers is achieved upon standing (1g of gravity). Centrifugation speeds the separation significantly. At about 75% IL (right hand vial in this example), clean sand and solvent diluted bitumen are readily obtained.
HOW GOOD IS THE SEPARATION?
Infrared spectroscopy confirms that clean separations are obtained. This technique involves passing an infrared beam through a thin film of a material or scattering the light from its surface. The amount of light absorbed as a function of the frequency of the light (measured in wavenumbers, cm–1) is then plotted. Different chemical groups absorb at different frequencies, providing a kind of “molecular fingerprint” of a material. The infrared spectrum of a parent oil sand is shown as the green plot in the figure below. It has bands (labeled) due to hydrocarbons (bitumen) which show up as fairly weak absorptions near 2800 cm–1. The recovered bitumen (red plot at top) has very strong bands in this region of the spectrum, as one would expect. On the other hand, the extracted minerals have almost undetectable bands in this region. Similarly, the very strong mineral bands below 2000 cm–1 are absent in the spectrum of the recovered oil.
Similar results are obtained in extractions from other types of samples. A visually compelling example is the clean up of weathered oil in the form of tar balls obtained from a beach in Alabama a few months after the Deepwater Horizon disaster. The appearance of the contaminated sand before and after IL/diluent treatment is shown below. Spectroscopy confirmed a clean separation.
* US 8603326; US 8603327; CA 2764578; CA 2761201. Six New patent applications were also filed in 2016 describing processes based on inexpensive ionic solutions.