Fan, Xin
(2006)
OXYGENATED HYDROCARBON-BASED AND HYDROCARBON-BASED CO2 SOLUBLE SURFACTANTS.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
The objectives of this work are to design, synthesize, and evaluate hydrocarbon-based or oxygenated hydrocarbon-based CO2 soluble surfactants. These surfactants would be able to form stable water-in-CO2 microemulsions with polar microenvironments capable of dissolving polar species in the bulk non-polar CO2 solvent, or to form metal precursors which can be reduced to nanoparticles in the presence of stabilizing ligands, or to generate foams in-situ for enhanced oil recovery application. Several oxygenated hydrocarbons, including acetylated sugars, poly(propylene glycol), oligo(vinyl acetate), and highly branched methylated hydrocarbons were used generate CO2-soluble ionic surfactants. Surfactants with vinyl acetate tails yielded the most promising results, exhibiting levels of CO2 solubility comparable to those associated with fluorinated ionic surfactants. For example, a sodium sulfate with single, oligomeric vinyl acetate (VAc) tails consisting of 10 VAc repeat units was 7 wt% soluble in CO2 at 25 oC and 48 MPa. Upon introduction of water to these systems, only surfactants with the oligomeric vinyl acetate tails exhibited spectroscopic evidence of a polar environment that was capable of solubilizing the methyl orange into CO2-rich phase. Silver bis(3,5,5-trimethyl-1-hexyl) sulfosuccinate, Ag-AOT-TMH, was synthesized from hydrocarbon-based ionic surfactant of sodium bis(3,5,5-trimethyl-1-hexyl) sulfosuccinate, Na-AOT-TMH through ion exchange. Ag-AOT-TMH exhibits 1.2 wt% solubility in dense CO2 at 40 oC and 52 MPa. Silver nanoparticles were produced by reducing the supercritical CO2 solution containing 0.06 wt% Ag-AOT-TMH and 0.5 wt% perfluorooctanethiol (stabilizing ligand) using a reducing agent of NaBH4. Iso-stearic acid, a short, stubby compound with branched, methylated tails, as a hydrocarbon-based nonionic surfactant, has been shown to have high solubility in carbon dioxide. The solvation of the tails by carbon dioxide has made isostearic acid sterically stabilize metallic nanoparticles as a ligand. The stability of CO2-water emulsion formed by ionic and nonionic surfactants was studied in CO2 at 22 oC and 34.5 MPa for 0.01-1.0 wt% surfactant mixed with equivalent volumes of CO2 and water. Emulsion stability was monitored by observing the rate of collapse of the white, opaque middle-phase emulsion between the transparent CO2 and water phases and the steady-state volume of the emulsion. It was found that at surfactant concentration of 0.01 wt%, oligo(vinyl acetate)10 sodium sulfate displayed the best emulsion, taking over 450 minutes to collapse.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
2 June 2006 |
| Date Type: |
Completion |
| Defense Date: |
1 February 2006 |
| Approval Date: |
2 June 2006 |
| Submission Date: |
9 February 2006 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Chemical Engineering |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
Carbon Dioxide; CO2-philic; Foam; Microemulsion; Nanoparticle; Phase Behavior; Stability; Surfactant |
| Other ID: |
http://etd.library.pitt.edu/ETD/available/etd-02092006-121431/, etd-02092006-121431 |
| Date Deposited: |
10 Nov 2011 19:31 |
| Last Modified: |
19 Dec 2016 14:34 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/6342 |
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