High temperature ultralow water content carbon dioxide-in-water foam stabilized with viscoelastic zwitterionic surfactants.
Ultralow water content carbon dioxide-in-water (C/W) foams with gas phase volume fractions (ϕ) above 0.95 (that is <0.05 water) tend to be inherently unstable given that the large capillary pressures that cause the lamellar films to thin. Herein, we demonstrate that these C/W foams may be stabilized with viscoelastic aqueous phases formed with a single zwitterionic surfactant at a concentration of only 1% (w/v) in DI water and over a wide range of salinity. Moreover, they are stable with a foam quality ϕ up to 0.98 even for temperatures up to 120°C. The properties of aqueous viscoelastic solutions and foams containing these solutions are examined for a series of zwitterionic amidopropylcarbobetaines, R-ONHC3H6N(CH3)2CH2CO2, where R is varied from C12-14(coco) to C18(oleyl) to C22(erucyl). For the surfactants with long C18and C22tails, the relaxation times from complex rheology indicate the presence of viscoelastic wormlike micelles over a wide range in salinity and pH, given the high surfactant packing fraction. The apparent viscosities of these ultralow water content foams reached more than 120cP with stabilities more than 30-fold over those for foams formed with the non-viscoelastic C12-14surfactant. At 90°C, the foam morphology was composed of ∼35μm diameter bubbles with a polyhedral texture. The apparent foam viscosity typically increased with ϕ and then dropped at ϕ values higher than 0.95-0.98. The Ostwald ripening rate was slower for foams with viscoelastic versus non-viscoelastic lamellae as shown by optical microscopy, as a consequence of slower lamellar drainage rates. The ability to achieve high stabilities for ultralow water content C/W foams over a wide temperature range is of interest in various technologies including polymer and materials science, CO2enhanced oil recovery, CO2sequestration (by greater control of the CO2flow patterns), and possibly even hydraulic fracturing with minimal use of water to reduce the requirements for wastewater disposal.
McKetta Department of Chemical Engineering, University of Texas at Austin, United States.
Shehab
S
Alzobaidi
McKetta Department of Chemical Engineering, University of Texas at Austin, United States.
Chang
C
Da
McKetta Department of Chemical Engineering, University of Texas at Austin, United States.
Vu
V
Tran
Department of Petroleum & Geosystems Engineering, University of Texas at Austin, United States.
Maša
M
Prodanović
McKetta Department of Chemical Engineering, University of Texas at Austin, United States. Electronic address: kpj@che.utexas.edu.
Keith P
KP
Johnston
CO(2)-in-water foam; Foam stability; High internal phase foam; Surfactant-stabilized foam; Viscoelastic; Viscosity; Wormlike micelles