The solubilities of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) in supercritical CO2 (scCO2) in the presence of ethanol, 1-pentanol and 2,2,3,3,4,4,5,5-octafluoro-1-pentanol (F-pentanol) at 38.0 °C and different pressures were determined. It was found that AOT (0.01–0.07 M) could be solubilized in scCO2 with smaller amount of F-pentanol (0.20–0.30 M) compared with ethanol (1.00–1.40 M) and 1-pentanol (0.60–1.00 M), because F-pentanol has ‘CO2-philic’ fluorinated alkane chain. The phase behavior studies for AOT (0.03 M)/F-pentanol (0.18–0.35 M)/scCO2 system ranging in temperature from 38.0 to 52.2 °C and pressures up to 35.00 MPa indicated that the cloud point pressure of AOT decreased significantly with the addition of F-pentanol, and the lower temperature, the lower cloud point pressure of AOT especially at higher concentrations of F-pentanol. In addition, 0.016 M AOT/0.24 M F-pentanol/scCO2 system could solubilize a significant amount of water (, and ) at moderate conditions, which implied the formation of water-in-CO2 reverse microemulsions. Visual observation using a video camera on the solubilization of methyl orange (MO) further proved the existence of polar micro-water domains within the AOT W/C reverse microemulsions. Besides that, bio-macromolecules such as cytochrome c and lysozyme and 8-hydroxy-1,3,6-pyrenetrisulphonic acid trisodium salt (HPTS) characteristic of highly ionic property could be solubilized in the microemulsions, which was obviously reflected by the UV–vis spectra.
"researches have been conducted to find chemical modifiers that can alter the polarity of CO 2 and/or make chemical solutes more soluble in CO 2 (Ohgaki and Katayama, 1976; Suzuki et al., 1990; Wang et al., 2009a). It has found that the addition of co-solvents (such as ethanol, 1-pentanol, F-pentanol and trin-butylphosphate ) can effectively enhance the extraction rate and yield, which can also increase the solubility of polar compounds in CO 2 (Wang et al., 2005; Salgın, 2007; Liu et al., 2005). On the other hand, injection of CO 2 into oilfields has been used as an effective technique for improving oil recovery (IOR), and CO 2 foam is used to reduce the mobility of CO 2 and increase the sweeping efficiency of the CO 2 flooding. "
[Show abstract][Hide abstract] ABSTRACT: The dissolution of surfactant-like compounds in supercritical CO2 in presence of co-solvents was investigated. The solubility measurement was conducted using a visualized PVT cell combined with UV spectrophotometer method at different pressures and 313 K. The viscosity of mixtures of CO2 and co-solvents with or without dissolved surfactants was also measured at similar conditions using a capillary tube rheometer. Nonionic surfactants (N-NP-10c, branched alkylphenol ethoxylates and APG-1214, alkyl polyglucoside) and anionic surfactants (N-NP-15c-H, sulfonated alkylphenol ethoxylates) were studied, which are good CO2 foaming agents. Experimental results showed that increasing pressure and addition of co-solvents could effectively improve solubility of surfactants in supercritical CO2. The addition of ethanol as a co-solvent could increase N-NP-10c's solubility in CO2 from 0.15 g (100 g)−1 to 1.76 g (100 g)−1 (over 11 times). APG-1214 with a mixture of ethanol and ethylene glycol as co-solvents exhibited an immediate dissolution capability in CO2, and its solubility could reach up to 1.99 g (100 g)−1. The solubility of N-NP-15c-H in comparison with APG-1214 was relatively low, only 0.57 g (100 g)−1 was obtained with the same co-solvents and at similar conditions. The addition of ethanol into CO2 could slightly increase its viscosity, while the effect of ethylene glycol and surfactants was much higher than that of ethanol, which indicates that the dissolution of surfactants in CO2 with co-solvents involves complicated interactions between molecules.
Chemical Engineering Research and Design 10/2014; 94. DOI:10.1016/j.cherd.2014.10.002 · 2.28 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Silver and silver iodide nanocrystals have been synthesized in the water-in-CO(2) reverse microemulsions formed by the commonly used surfactant, sodium bis(2-ethylhexyl)sulfosuccinate (AOT), in the presence of 2,2,3,3,4,4,5,5-octafluoro-1-pentanol as cosurfactant. The nanometer-sized aqueous domains in the microemulsion cores not only act as nanoreactors, but the surfactant interfacial monolayer also helps the stabilization of the metal and semiconductor nanoparticles. The transmission electron microscopy results show that silver and silver iodide nanocrystals with average diameters of 6.0 nm (standard deviation, SD=1.3 nm) and 5.7 nm (SD=1.4 nm), respectively, were formed. The results indicate that the method can be utilized as a general and economically viable approach for the synthesis of metal and semiconductor quantum dots in environmentally benign supercritical carbon dioxide.
[Show abstract][Hide abstract] ABSTRACT: The phase behavior of poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) triblock copolymers (PEO-PPO-PEO Pluronics) in liquid and supercritical carbon dioxide has been studied by cloud point measurements. It shows that such trade hydrocarbonated surfactants are fairly soluble (0.1 wt.%) in carbon dioxide in relatively mild conditions of temperature and pressure (T < 65 °C, P < 30 MPa). An empirical model based on the molecular weight of the copolymer has been proposed to predict the pressure–temperature phase diagram for a series of Pluronics (10 wt.% of ethylene oxide). Furthermore, the water/CO2 interfacial tension has been measured to investigate the interactions between water and the polar moieties of the surfactants (PEO blocks and hydroxyl end-groups) as well as the interactions between CO2 and the “CO2-philic” moiety of the surfactants (PPO block). An interfacial saturation concentration was evidenced and it was shown to depend on the temperature at a given pressure. The cloud point curves and interfacial tension data are fully consistent with a change in the affinity of the surfactant for CO2 versus pressure and temperature. A correlation between CO2-philic characteristics and surface active properties of the copolymers is given.
Journal of Supercritical Fluids The 08/2007; 42(1-42):69-79. DOI:10.1016/j.supflu.2007.01.010 · 2.37 Impact Factor
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