|Separation of bitumen from a Canadian oil sand sample using an ionic liquid. Click to enlarge.|
A team of researchers at Penn State has developed a new, more environmentally friendly method of separating bitumen from oil sands utilizing ionic liquids (IL). The method is also capable of cleaning oil spills from beaches and separating oil from drill cuttings, the solid particles that must be removed from drilling fluids in oil and gas wells. The Penn State separation method uses very little energy and water, and all solvents are recycled and reused.
Paul Painter, professor of polymer science in the Department of Materials Science and Engineering at Penn State, and his group have spent the past 18 months developing a technique that uses ionic liquids (salt in a liquid state) to facilitate separation. The separation takes place at room temperature without the generation of waste process water.
|Oil sands (also called tar or bituminous sands) are complex mixtures of sand, clays, water and bitumen, a “heavy” or highly viscous oil.|
|Oil sands represent approximately two-thirds of the world’s estimated oil reserves. Canada is the world’s major producer of unconventional oil from sands, and the US imports more than 1 million barrels of oil per day from Canada, about twice as much as from Saudi Arabia. Much of this oil is produced from the Alberta tar sands.|
|Significant quantities of oil sands (estimated to contain 32 billion barrels of oil) can also be found in Eastern Utah in the US.|
|Extraction and separation of bitumen from surface-mined oil sands involves the use of significant amounts of energy and water. The water used in the process is ultimately stored in vast tailing ponds. It is a complex mixture of water, dissolved salts, minerals, residual bitumen, surfactants released from the bitumen and other materials used in processing and is acutely toxic to aquatic life.|
|In addition, the requirement for large amounts of water can deplete the supply of local fresh water resources.|
Essentially all of the bitumen is recovered in a very clean form, with no detectable mineral fines, which interact preferentially with the IL, and no contamination from the IL. The sand is also recovered in an uncontaminated form after removing residual IL with small amounts of cold water. Because of the unique properties of ILs, the water and IL used in this process can be readily separated, recovered and recycled through the system.
The separation is usually conducted in conjunction with a non-polar solvent to lower the viscosity of the tar or bitumen and facilitate separation. Because the bitumen, solvents and sand/clay mixture separate into three distinct phases, each can be removed separately and the solvent can be reused.
The process can also be used to extract oil and tar from beach sand after oil spills, such as the Exxon Valdez and Deepwater Horizon incidents. Unlike other methods of cleanup, the Penn State process completely removes the hydrocarbons, and the cleaned sand can be returned to the beach instead of being sent to landfills. In an experiment using sand polluted by the BP oil spill, the team was able to separate hydrocarbons from the sand within seconds. A small amount of water was used to clean the remaining ionic liquids from the sand, but that water was also recoverable.
It was so clean you could toss it back on the beach. Plus, the only extra energy you need is enough to stir the mixture.—Aron Lupinsky, a researcher in Painter’s group
The researchers work with a group of ionic liquids based on 1-alkyl-3-methylimidazolium cations, a positively charged material with high chemical and thermal stability, a low degree of flammability, and almost negligible vapor pressure, which makes recovering the ionic liquid relatively simple. The properties of these materials can be “tailored” by varying the nature of the substituents (R) on the ring and the nature of the anion.
The team has built a functioning bench top model system and is in the process of reducing their discovery to practice for patenting.