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Phase-Change Solvents for the Capture and Release of CO2 and CO2-Soluble Surfactants for Stabilization of CO2-in-Brine Foams

Wei, Bing (2011) Phase-Change Solvents for the Capture and Release of CO2 and CO2-Soluble Surfactants for Stabilization of CO2-in-Brine Foams. Master's Thesis, University of Pittsburgh. (Unpublished)

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The first intention of this research is to identify specific CO2-philic solids from two candidates, namely sugar acetates and tert-butylated aromatics, which can be used to separate high pressure CO2 from H2. In this work, many of these solids were found to melt in the presence of high pressure CO2 (600 ¨C 1000 psi) and absorb large amounts of CO2. It was hoped that upon exposure to a 1:1 CO2/H2 high pressure gas mixture that was selected to be representative of a shifted gasifier effluent stream, the solid would melt and selectively absorb CO2. Only one candidate, glucose pentaacetate, was found to melt in the presence of the gas mixture at 25 oC. The pressure of the system was ~6000 psia, which is unrealistically high for the commercial application of this process. Therefore mixed gas solubilities in the molten phase were not determined.In a second project, a strategy for using CO2-soluble compounds to decrease the mobility of dense CO2 in porous media was investigated. It is to inject a CO2 surfactant solution into the porous media, which contains both brine and oil, thereby generating a low mobility emulsion or foam of CO2 droplets separated by surfactant-stabilized brine lamellae that bridge pore throats. In this work, the surfactants were screened by assessing their ability to stabilize foams when equal volumes of CO2 and brine were mixed with the amount of surfactant capable of dissolving in the CO2 at test conditions (e.g. 25 oC and 1300 psia). Stability was assessed by monitoring the rate of collapse of the foam and the appearance of clear zones of excess water and CO2.We have established the identity of several non-ionic, hydrocarbon-based, commercially available, inexpensive surfactants that can dissolve in CO2 at typical EOR reservoirs conditions to a high enough concentration (~0.02 - 0.20 wt% ) to form relatively stable emulsions/foams of liquid or supercritical CO2 droplets separated by films of brine. Although these surfactants are CO2-soluble, they are even more water-soluble, therefore they tend to partition into the low-volume brine phase and stabilize the emulsion form emulsions in which the brine is the low-volume (e.g. 10vol%) continuous phase, in accordance with Bancroft¡¯s rule. The most effective thickeners were branched alkyl phenol ethoxylates, linear alkyl phenol ethoxylates, and linear alkyl ethoxylates. Linear ethoxylated alcohols was ineffective foam stabilizers.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Wei, Bingbiw7@pitt.eduBIW7
Date: 26 January 2011
Date Type: Completion
Defense Date: 22 November 2010
Approval Date: 26 January 2011
Submission Date: 2 November 2010
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: MSChE - Master of Science in Chemical Engineering
Thesis Type: Master's Thesis
Refereed: Yes
Uncontrolled Keywords: carbon dioxide; foam stability; solubility
Other ID:, etd-11022010-195357
Date Deposited: 10 Nov 2011 20:03
Last Modified: 15 Nov 2016 13:51


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