Carbon dioxide-active surfactants

For the stabilization of various insoluble hydrocarbon polymers in carbon dioxide, it has been found that no one surfactant works well for all systems. Therefore it has become necessary to tailor the surfactants to the specific polymerization reaction. Through variation of not only the composition of the surfactants, but also their architectures, surfactants have been molecularly-engineered to be surface active—partitioning at the interface between the growing polymer particle and the CO2 continuous phase. The surfactants utilized to date include poly(FOA) homopolymer, poly(dimethylsiloxane) homopolymer with a polymerizable endgroup, poly(styrene-b-FOA), and poly(styrene-b-dimethylsiloxane). Through the utilization of these surfactants, the successful dispersion polymerization of methyl methacrylate (MMA), styrene, and 2,6-dimethylphenol in CO2 has been demonstrated. 

Specifically, EOR activity can be classified into three major types (1) chemical, (2) miscible displacement, and (3) thermal. The first category includes the injection of surfactants (micellar), polymers, alkaline (caustic), and carbon dioxide. In miscible displacement, a gas or liquid hydrocarbon is injected into the reservoir where it becomes miscible with the hydrocarbons... 

Harrison KL, daRocha SRP, Yates MZ, Johnston KP, Canelas D, DeSimone JM. Interfacial activity of polymeric surfactants at the polystyrene-carbon dioxide interface. Langmuir 1998 14 6855-6863. 

About 150 lipid molecules were present per 1 of enzyme. It was used to esterify 1-phenylethanol with lauric acid in isooctane, giving 95% conversion in 2 h. A lipid-coated lipase has also been used to esterify lauric acid with glycerol in sc carbon dioxide with 90% conversion.98 Catalase with less than 5% of its surface amino groups modified by the nonionic surfactant 9.7 had a higher activity in 1,1,1-trichloroethane than when the enzyme was conjugated with polyethylene glycol.99... 

To control the reaction rate of the acid, retarders such as alkyl sulfonates, alkyl phosphonates and alkyl amines are used to form hydrophobic films on carbonate surfaces. These protective films act as a barrier to slow acid attack. Another method involves the use of foaming agents to stabilize the carbon dioxide foam that is created when CO2 is released as a product of the acidetching reaction. This CO2 foam acts as a barrier to slow acid attack. Yet another method for controlling the acid activity in an oil well is the use of emulsions containing kerosene or diesel as the continuous oil phase and hydrochloric acid as the dispersed aqueous phase. Acid-in-oil emulsions are most commonly used because oil separates the acid from the carbonate surface (and from machine parts, thus reducing the level of corrosion). Moreover, acid reaction rates can be further decreased by surfactant retarders that increase the wettability of the carbonate surface for oil. 

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