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Title: Phase Behavior of Oxygen-Containing Polymers in CO2

Abstract

The cloud point curves of a series of oxygen-containing polymers in CO2 were measured to attempt to deduce the effect of oxygen functional groups within a polymer on the polymer/CO2 phase behavior. The addition of an ether oxygen to a hydrocarbon polymer, either in the backbone or the side chain, enhances "CO2-philicity" by providing sites for specific interactions with CO2 as well as by enhancing the entropy of mixing by creating more flexible chains with higher free volume. Ab initio calculations show that both ether and ester oxygens provide very attractive interaction sites for CO2 molecules. The binding energy for an isolated ether oxygen with CO2 is larger in magnitude than that for a carbonyl oxygen/CO2 complex. However, acetate functionalized polymers are more CO2-soluble than polymers with only ether functionalities-possibly because acetate functional groups contain a total of three binding modes for CO2 interactions, compared with only one for the ether functional group. Experiments clearly indicate that adding a single methylene group as a spacer between a polymer backbone and either an ether or acetate group exhibits a strong deleterious effect on phase behavior. This effect cannot be explained from our ab initio calculations.

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
National Energy Technology Laboratory (NETL), Pittsburgh, PA, and Morgantown, WV
Sponsoring Org.:
USDOE - Office of Fossil Energy (FE)
OSTI Identifier:
919547
Report Number(s):
DOE/NETL-IR-2007-114
Journal ID: ISSN 0024-9297; TRN: US200822%%289
DOE Contract Number:
None cited
Resource Type:
Journal Article
Resource Relation:
Journal Name: Macromolecules; Journal Volume: 40; Journal Issue: 4
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CATALYTIC EFFECTS; CARBON DIOXIDE; OXYGEN; POLYMERS; PHASE STUDIES; POLYETHYLENE GLYCOLS; POLYESTERS; ACETATES; MOLECULAR STRUCTURE

Citation Formats

Killic, Sevgi, Michalik, Stephen, Wang, Yang, Johnson, J.K., Enick, R.M., and Beckman, E.J.. Phase Behavior of Oxygen-Containing Polymers in CO2. United States: N. p., 2007. Web. doi:10.1021/ma061422h.
Killic, Sevgi, Michalik, Stephen, Wang, Yang, Johnson, J.K., Enick, R.M., & Beckman, E.J.. Phase Behavior of Oxygen-Containing Polymers in CO2. United States. doi:10.1021/ma061422h.
Killic, Sevgi, Michalik, Stephen, Wang, Yang, Johnson, J.K., Enick, R.M., and Beckman, E.J.. Tue . "Phase Behavior of Oxygen-Containing Polymers in CO2". United States. doi:10.1021/ma061422h.
@article{osti_919547,
title = {Phase Behavior of Oxygen-Containing Polymers in CO2},
author = {Killic, Sevgi and Michalik, Stephen and Wang, Yang and Johnson, J.K. and Enick, R.M. and Beckman, E.J.},
abstractNote = {The cloud point curves of a series of oxygen-containing polymers in CO2 were measured to attempt to deduce the effect of oxygen functional groups within a polymer on the polymer/CO2 phase behavior. The addition of an ether oxygen to a hydrocarbon polymer, either in the backbone or the side chain, enhances "CO2-philicity" by providing sites for specific interactions with CO2 as well as by enhancing the entropy of mixing by creating more flexible chains with higher free volume. Ab initio calculations show that both ether and ester oxygens provide very attractive interaction sites for CO2 molecules. The binding energy for an isolated ether oxygen with CO2 is larger in magnitude than that for a carbonyl oxygen/CO2 complex. However, acetate functionalized polymers are more CO2-soluble than polymers with only ether functionalities-possibly because acetate functional groups contain a total of three binding modes for CO2 interactions, compared with only one for the ether functional group. Experiments clearly indicate that adding a single methylene group as a spacer between a polymer backbone and either an ether or acetate group exhibits a strong deleterious effect on phase behavior. This effect cannot be explained from our ab initio calculations.},
doi = {10.1021/ma061422h},
journal = {Macromolecules},
number = 4,
volume = 40,
place = {United States},
year = {Tue Feb 20 00:00:00 EST 2007},
month = {Tue Feb 20 00:00:00 EST 2007}
}
  • Porous polymers containing various metal chelates bonded to nitrogen functionalities on the surface of the polymer have been synthesized and found to bind oxygen reversibly. The stationary phases containing (5,5'-(1,2-ethanediyldinitrilo)-bis(2,2,7-trimethyl-3-octanonato))cobalt(II) were found to be the most suitable of the phases investigated for separating oxygen from argon, nitrogen, and carbon monoxide. At ambient temperatures, near 25/sup 0/C, the reversible interaction of molecular oxygen with the transition-metal complex bonded to the stationary phase results in a marked increase in the retention time of oxygen, relative to species that have similar retention times in columns that do not contain the metal chelate. Themore » stationary phase can be used alone to achieve the separation of low molecular weight gases or in series with another column. The metal chelate stationary phase is selective for oxygen and little change in the retention time of oxygen is observed after hundreds of injections over a several-month period, indicating that no appreciable degradation of the stationary phase had taken place under these conditions. 30 references, 6 figures, 2 tables.« less
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  • Phase equilibria in mixtures containing carbon dioxide, water, and chloride salts have been investigated using a combination of solubility measurements and thermodynamic modeling. The solubility of water in the CO2-rich phase of ternary mixtures of CO2, H2O and NaCl or CaCl2 was determined, using near infrared spectroscopy, at 90 atm and 40 to 100 °C. These measurements fill a gap in the experimental database for CO2 water salt systems, for which phase composition data have been available only for the H2O-rich phases. A thermodynamic model for CO2 water salt systems has been constructed on the basis of the previously developedmore » Mixed-Solvent Electrolyte (MSE) framework, which is capable of modeling aqueous solutions over broad ranges of temperature and pressure, is valid to high electrolyte concentrations, treats mixed-phase systems (with both scCO2 and water present) and can predict the thermodynamic properties of dry and partially water-saturated supercritical CO2 over broad ranges of temperature and pressure. Within the MSE framework the standard-state properties are calculated from the Helgeson-Kirkham-Flowers equation of state whereas the excess Gibbs energy includes a long-range electrostatic interaction term expressed by a Pitzer-Debye-Hückel equation, a virial coefficient-type term for interactions between ions and a short-range term for interactions involving neutral molecules. The parameters of the MSE model have been evaluated using literature data for both the H2O-rich and CO2-rich phases in the CO2 - H2O binary and for the H2O-rich phase in the CO2 - H2O - NaCl / KCl / CaCl2 / MgCl2 ternary and multicompontent systems. The model accurately represents the properties of these systems at temperatures from 0°C to 300 °C and pressures up to ~4000 atm. Further, the solubilities of H2O in CO2-rich phases that are predicted by the model are in agreement with the new measurements for the CO2 - H2O - NaCl and CO2 - H2O - CaCl2 systems. Thus, the model can be used to predict the effect of various salts on the water content and water activity in CO2-rich phases on the basis of parameters determined from the properties of aqueous systems. Given the importance of water activity in CO2-rich phases for mineral reactivity, the model can be used as a foundation for predicting mineral transformations across the entire CO2/H2O composition range from aqueous solution to anhydrous scCO2. An example application using the model is presented which involves the transformation of forsterite to nesquehonite as a function of temperature and water content in the CO2-rich phase.« less