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Title: Determination of Organic Partitioning Coefficients in Water-Supercritical CO 2 Systems by Simultaneous in Situ UV and Near-Infrared Spectroscopies

CO2 injected into depleted oil or gas reservoirs for long-term storage has the potential to mobilize organic compounds and distribute them between sediments and reservoir brines. Understanding this process is important when considering health and environmental risks, but little quantitative data currently exists on the partitioning of organics between supercritical CO2 and water. In this work, a high-pressure, in situ measurement capability was developed to assess the distribution of organics between CO2 and water at conditions relevant to deep underground storage of CO2. The apparatus consists of a titanium reactor with quartz windows, near-infrared and UV spectroscopic detectors, and switching valves that facilitate quantitative injection of organic reagents into the pressurized reactor. To demonstrate the utility of the system, partitioning coefficients were determined for benzene in water/supercritical CO2 over the range 35-65 °C and approximately 25-150 bar. Density changes in the CO2 phase with increasing pressure were shown to have dramatic impacts on benzene's partitioning behavior. Our partitioning coefficients were approximately 5-15 times lower than values previously determined by ex situ techniques that are prone to sampling losses. The in situ methodology reported here could be applied to quantify the distribution behavior of a wide range of organic compounds thatmore » may be present in geologic CO2 storage scenarios.« less
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Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 0013-936X; 47864; AA7050000
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Environmental Science and Technology; Journal Volume: 50; Journal Issue: 11
American Chemical Society (ACS)
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org:
USDOE Office of Fossil Energy (FE)
Country of Publication:
United States
Organic Partitioning Coefficients; Supercritical CO2; in situ; Environmental Molecular Sciences Laboratory