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Thickening supercritical CO2 at high temperatures with rod-like reverse micelles
,
Yuuki Sato,
Sajad Kiani,
Shirin Alexander ,
Tretya Ardyani ,
Azmi Mohamed,
Robert M. Enick,
Sarah E. Rogers,
Christopher Hill ,
Julian Eastoe
Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume: 686
Swansea University Author:
Shirin Alexander
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DOI (Published version): 10.1016/j.colsurfa.2024.133302
Abstract
Earlier studies demonstrated the ability of some fluorinated surfactants to form rod-like reverse micelles with the ability to thicken water/supercritical CO2 (scCO2) mixtures at temperatures below 45 ºC [Langmuir 26 (2010) 83–88. Soft Matter 8 (2012) 7044–7055. Colloids and Surfaces B, 168 (2018),...
| Published in: | Colloids and Surfaces A: Physicochemical and Engineering Aspects |
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| ISSN: | 0927-7757 |
| Published: |
Elsevier BV
2024
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| Online Access: |
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| URI: | https://cronfa.swan.ac.uk/Record/cronfa65642 |
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| Abstract: |
Earlier studies demonstrated the ability of some fluorinated surfactants to form rod-like reverse micelles with the ability to thicken water/supercritical CO2 (scCO2) mixtures at temperatures below 45 ºC [Langmuir 26 (2010) 83–88. Soft Matter 8 (2012) 7044–7055. Colloids and Surfaces B, 168 (2018), 201–210.]. Such viscosity enhancement of scCO2 is known to increase sweep efficiency for oil recovery with CO2 flooding. However, temperatures of up to ∼100 ºC in conventional reservoirs are much higher than those employed in laboratory studies, and tend to weaken inter- and intra-molecular interactions between surfactant molecules, discouraging rod-like reverse micelle formation. With the aim of designing surfactants which form rod-like reverse micelles and thicken CO2 at high temperatures, this study examined phase behavior, nanostructures of reverse micelles and thickening ability of double ω-hydroperfluorocarbon-tail anionic surfactants in W/scCO2 mixtures at temperatures of 35 - 75 ºC and pressure of 80 - 400 bar with different water-to-surfactant molar ratios (W0). The measured CO2 viscosity increased by 1.9–2.2 × for double-chain surfactants M(di-HCF6)x (counterion Mx+ = Ni2+ and Co2+) at 40 mM, over the experimental temperature range. On the other hand, the shorter chain H(CF2)4CH2 twin-tail surfactants M(di-HCF4)x and Na(di-HCF6) gave only 1.1–1.5 × viscosity enhancements. The maximum thickening ability of M(di-HCF6)2 was at W0 = 10 in the W0 range of 5–20 75 ºC and 350 bar. High pressure and high temperature small-angle neutron scattering (SANS) was used determine the micellar structure in these systems, and rod micelles of aspect ratios of 4.5–6.5 were found. The results clearly suggest that ω-hydroperfluorohexyl-tails and divalent counterions induce the formation of rod-like reverse micelles in W/CO2 mixtures, even at high temperatures commensurate with in-reservoir conditions. |
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| Keywords: |
Supercritical CO2ω-hydroperfluorocarbon, Viscosity, Rod-like reverse micelle, Small-angle neutron scattering |
| College: |
Faculty of Science and Engineering |
| Funders: |
This project was supported by JSPS [KAKENHI, Grant-in-Aid for Scientific Research (B), No. 23H01750 and 19H02504, and International Exchanges 2021 Cost Share (JSPS) award 1845272]. We also acknowledge STFC for the allocation of beam time, travel, and consumables grants at ISIS. The authors acknowledge Shared Facility Center for Science and Technology, Hirosaki University (SFCST) for 1H NMR and FT-IR spectra measurements and elemental analysis. CH acknowledges JSPS for support as a JSPS International Research Fellow (Graduate School of Science and Technology, Hirosaki University). |