Oil & Natural Gas Projects
Exploration and Production Technologies
Use of Ionic Liquids in Produced-Water Clean-up
This project was funded through DOE's Natural Gas and Oil Technology Partnership
Program. The program establishes alliances that combine the resources and experience
of the nation's petroleum industry with the capabilities of the national laboratories
to expedite research, development, and demonstration of advanced technologies
for improved natural gas and oil recovery.
The goal was to use novel hydrophobic ionic liquid solvents for removal of organics
from produced water. Chemical distribution factors were measured for major classes
of organics: acids, paraffins, ketones, alcohols, and aromatics. The efficiency
of the process was demonstrated using a centrifugal contactor for separation
of immiscible liquid phases.
Oak Ridge National Laboratory (ORNL)
Oak Ridge, TN
Shell Oil Co.
San Ramon, CA
The project has demonstrated that hydrophobic ionic liquids can preferentially
remove selected organics from an aqueous phase. Efficient separation techniques
have been developed using state-of-the-art centrifugal contactor technology.
The produced-water waste stream is of concern to all oil producers, large companies
as well as small, independent producers. Offshore and onshore facilities alike
will benefit from the ability to remediate produced water using methods that
are both efficient and cost-effective. Research into a new approach, such as
applying ionic liquids to solving problems with produced water, will assist
all producers to comply with environmental regulations, ensuring a diverse and
secure energy supply.
Discharge of produced water in the Gulf of Mexico is regulated by National Pollutant
Discharge Elimination System permits, which specify that total oil and grease
in the water be below a daily maximum of 42 ppm. Remediation of the billions
of barrels of water per annum of produced water often gives variable results
because of the chemistry of the oil and its ability to buffer against pH changes.
The problem is particularly severe for new wells, where the properties of the
oil may change during production, and the amounts and types of the water-soluble
organic compounds are not well-known. Hence the goal of this project will be
to introduce a new approach to produced-water remediation, through solvent extraction
using ionic liquids.
In the project, researchers:
- Selected ionic liquid solvents based on physical and chemical properties.
- Tested organic removal under conditions of temperature, salinity, and pH
comparable to that found in produced water and published results.
- Demonstrated separation in a centrifugal contactor.
- Measured bulk-phase and interfacial properties key to separation efficiencies
and published results.
Current Status (August 2005)
In this project, ORNL and industry partners have addressed questions regarding
efficacy, regeneration, and selectivity of ionic liquid-based removal of polar
organic compounds from produced water. For produced-water remediation, the ionic
liquid must be immiscible with the aqueous phase. Hydrophobic ionic liquids
have been synthesized in-house and have been tested in three ways:
- In liquid-liquid extraction of produced water contaminants (complete).
- Phase separation with a brine in a centrifugal contactor that has previously
been used for oil/water separations (in progress).
- Physical properties measurements (in progress).
Effluent samples collected from NaCl:bmim TF2N separated in a centrifugal contactor.
The work was published in two papers presented at the Separation Science and
Technology Conference in Gatlinberg, KY, in October 2003 and at the National
AICHE meeting in November 2004.
McFarlane, J., Ridenour, W.B., Luo, H., Hunt, R.D., DePaoli, D.W., and Ren,
R.X., 2005, Room-Temperature Ionic Liquids for Separating Organics from Produced
Water, Separations Science and Technology 40 (6), 1245-1265.
Toh, S.L.I., McFarlane, J., Tsouris, C., DePaoli, D.W., Luo, H., Dai, S., Room-Temperature
Ionic Liquids in Liquid-Liquid Extraction: Effects of Solubility in Aqueous
Solutions on Surface Properties.
Project Start: March 1, 2003
Project End: September 30, 2005; no-cost extension to December 31, 2005
Anticipated DOE Contribution: $390,000
Performer Contribution: Industry (in kind): $78,000 (20% of total)
NETL - Rhonda Jacobs (firstname.lastname@example.org or 918-699-2037)
ORNL - David DePaoli (email@example.com or 865-574-6817)