478753 High Temperature Ultradry Carbon Dioxide-in-Water Foam Stabilized with Viscoelastic Surfactants

Tuesday, November 15, 2016: 10:10 AM
Union Square 22 (Hilton San Francisco Union Square)
Keith P. Johnston, McKetta Department of Chemical Engineering, The University of Texas at Austin, Austin, TX, Shehab Alzobaidi, Chemical engineering, Mississippi state university, STARKVILLE, MS, Chang Da, Chemical and Biomolecular Engineering, Rice University, Houston, TX and Vu Tran, Chemical Engineering, Purdue University, West Lafayette, IN

Ultradry carbon dioxide- in-water (C/W) foams with gas phase volume fractions () above 0.95 tend to be inherently unstable, as the large capillary pressure between the foam bubbles accelerates coalescence. Herein, we demonstrate that these ultradry C/W foams may be stabilized with viscoelastic aqueous phases formed with a single surfactant at a concentration of only 1% (w/v). The C/W foams are stable in DI water and over a wide range of salinity. Moreover, they are stable even for temperatures up to 120oC and with  up to 0.99. The properties of the foams and the aqueous viscoelastic solutions are examined for a series of surfactants. For our surfactants, the relaxation times from complex rheology indicate the formation of viscoelastic wormlike micelles over a wide range in salinity and pH, given the high surfactant packing fraction. At 90 oC and above 0.9, the foam morphology was composed of ~ 35 m diameter bubbles with a polyhedral texture. The apparent viscosities of these ultradry foams reached more than 120 cP with stabilities more than 30-fold over those for foams formed with the non-viscoelastic surfactants. The highly viscous lamellae remain thicker, due to the slower drainage rate, therefore resulting in slower Ostwald ripening relative to foams with non-viscoelastic lamellae. This is shown by measuring the change in bubble diameter with time via optical microscopy. Ultradry C/W foam at elevated temperatures could potentially be useful for CO2 sequestration, improved oil recovery or for hydraulic fracturing with minimal use of water to reduce the requirements for wastewater disposal.

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