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Title: Near-infrared spectroscopic investigation of water in supercritical CO2 and the effect of CaCl2

Abstract

Near-infrared (NIR) spectroscopy was applied to investigate the dissolution and chemical interaction of water dissolved into supercritical carbon dioxide (scCO2) and the influence of CaCl2 in the co-existing aqueous phase at fo empe e : 40 50 75 nd 100 C at 90 atm. Consistent with the trend of the vapor pressure of water, the solubility of pure water in scCO2 inc e ed f om 40 °C (0.32 mole%) o 100 °C (1.61 mole%). The presence of CaCl2 negatively affects the solubility of water in scCO2: at a given temperature and pressure the solubility of water decreased as the concentration of CaCl2 in the aqueous phase increased, following the trend of the activity of water. A 40 °C, the water concentration in scCO2 in contact with saturated CaCl2 aqueous solution was only 0.16 mole%, a drop of more than 50% as compared to pure water while that a 100 °C was 1.12 mole%, a drop of over 30% as compared to pure water, under otherwise the same conditions. Analysis of the spectral profiles suggested that water dissolved into scCO2 exists in the monomeric form under the evaluated temperature and pressure conditions, for both neat water and CaCl2 solutions. However,more » its rotational degrees of freedom decrease at lower temperatures due to higher fluid densities, leading to formation of weak H2O:CO2 Lewis acid-base complexes. Similarly, the nearly invariant spectral profiles of dissolved water in the presence and absence of saturated CaCl2 under the same experimental conditions was taken as evidence that CaCl2 dissolution in scCO2 was limited as the dissolved Ca2+/CaCl2 would likely be highly hydrated and would alter the overall spectra of waters in the scCO2 phase.« less

Authors:
; ; ; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
1072896
Report Number(s):
PNNL-SA-89926
Journal ID: ISSN 0378-3812; 47427; 39937; KC0302060; KC0303020
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Fluid Phase Equilibria
Additional Journal Information:
Journal Volume: 338; Journal Issue: C; Journal ID: ISSN 0378-3812
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Environmental Molecular Sciences Laboratory

Citation Formats

Wang, Zheming, Felmy, Andrew R., Thompson, Christopher J., Loring, John S., Joly, Alan G., Rosso, Kevin M., Schaef, Herbert T., and Dixon, David A. Near-infrared spectroscopic investigation of water in supercritical CO2 and the effect of CaCl2. United States: N. p., 2013. Web. doi:10.1016/j.fluid.2012.11.012.
Wang, Zheming, Felmy, Andrew R., Thompson, Christopher J., Loring, John S., Joly, Alan G., Rosso, Kevin M., Schaef, Herbert T., & Dixon, David A. Near-infrared spectroscopic investigation of water in supercritical CO2 and the effect of CaCl2. United States. https://doi.org/10.1016/j.fluid.2012.11.012
Wang, Zheming, Felmy, Andrew R., Thompson, Christopher J., Loring, John S., Joly, Alan G., Rosso, Kevin M., Schaef, Herbert T., and Dixon, David A. Tue . "Near-infrared spectroscopic investigation of water in supercritical CO2 and the effect of CaCl2". United States. https://doi.org/10.1016/j.fluid.2012.11.012.
@article{osti_1072896,
title = {Near-infrared spectroscopic investigation of water in supercritical CO2 and the effect of CaCl2},
author = {Wang, Zheming and Felmy, Andrew R. and Thompson, Christopher J. and Loring, John S. and Joly, Alan G. and Rosso, Kevin M. and Schaef, Herbert T. and Dixon, David A.},
abstractNote = {Near-infrared (NIR) spectroscopy was applied to investigate the dissolution and chemical interaction of water dissolved into supercritical carbon dioxide (scCO2) and the influence of CaCl2 in the co-existing aqueous phase at fo empe e : 40 50 75 nd 100 C at 90 atm. Consistent with the trend of the vapor pressure of water, the solubility of pure water in scCO2 inc e ed f om 40 °C (0.32 mole%) o 100 °C (1.61 mole%). The presence of CaCl2 negatively affects the solubility of water in scCO2: at a given temperature and pressure the solubility of water decreased as the concentration of CaCl2 in the aqueous phase increased, following the trend of the activity of water. A 40 °C, the water concentration in scCO2 in contact with saturated CaCl2 aqueous solution was only 0.16 mole%, a drop of more than 50% as compared to pure water while that a 100 °C was 1.12 mole%, a drop of over 30% as compared to pure water, under otherwise the same conditions. Analysis of the spectral profiles suggested that water dissolved into scCO2 exists in the monomeric form under the evaluated temperature and pressure conditions, for both neat water and CaCl2 solutions. However, its rotational degrees of freedom decrease at lower temperatures due to higher fluid densities, leading to formation of weak H2O:CO2 Lewis acid-base complexes. Similarly, the nearly invariant spectral profiles of dissolved water in the presence and absence of saturated CaCl2 under the same experimental conditions was taken as evidence that CaCl2 dissolution in scCO2 was limited as the dissolved Ca2+/CaCl2 would likely be highly hydrated and would alter the overall spectra of waters in the scCO2 phase.},
doi = {10.1016/j.fluid.2012.11.012},
url = {https://www.osti.gov/biblio/1072896}, journal = {Fluid Phase Equilibria},
issn = {0378-3812},
number = C,
volume = 338,
place = {United States},
year = {2013},
month = {1}
}