WO2002036859A1

WO2002036859A1 - Methods for increasing ionic conductivity in carbon dioxide and mixtures

Info

Publication number: WO2002036859A1
Application number: PCT/US2001/045574
Authority: WO
Inventors: Peter S. Fedkiw; Jin Jun; Joseph M. Desimone
Original assignee: University of North Carolina at Chapel Hill; North Carolina State University
Current assignee: University of North Carolina at Chapel Hill; North Carolina State University
Priority date: 2000-11-03
Filing date: 2001-10-24
Publication date: 2002-05-10
Anticipated expiration: 2003-05-03

Abstract

A composition of matter comprises an ionic compound; and a carbon dioxide containing fluid having at least one salt dissolved therein comprising at least one CO2-philic segment. The carbon dioxide containing fluid displays a higher ionic conductivity relative to a carbon dioxide containing fluid that does not contain the at least one salt.

Description

METHODS FOR INCREASING IONIC CONDUCTIVITY IN CARBON DIOXIDE AND MIXTURES

Field of the Invention The invention generally relates to compositions of matter which include carbon dioxide and exhibit increased ionic conductivity, along with methods of increasing the ionic conductivity of such compositions of matter.

Background of the Invention Electrochemical processes are currently gaining an increased amount of attention due to their ability to be potentially employed in a wide number of applications. For example, electrochemical oxidation in principal is a potentially more environmentally benign route for the destruction of chemical waste in comparison to thermal oxidation or wet-chemistry techniques. Specifically, the generation of noxious off-gases is minimized if not entirely eliminated, and mineral acids and salts are typically created by the electrooxidation of hetero-atom organics. In an electrochemical oxidation, refractory chemicals may be destroyed at relatively mild processing conditions by supplying adequate energy through the cell voltage. In addition to chemical destruction, electrochemical synthesis is believed to be a viable

"green" route for chemical manufacture in that the electrodes themselves may be capable of functioning as the site for oxidation and reduction. Consequently, spent chemical agents are usually not generated, and accompanying separation processes are typically not necessary. Furthermore, controlling the electrical current may set the rate of reaction, or alternatively, the electrode potential can be controlled to obtain specificity for the desired product(s). See e.g., D. Genders and N. Weinberg (eds.)

Electrochemistry for a Cleaner Environment, The Electrosynthesis Company (1992).

Electrochemical processes for waste destruction or chemicals manufacture in a supercritical fluid (SCF) presents a potential opportunity to couple and exploit the tunable solvent properties of SCFs with the controllability of electrochemical reactions. Processes for carrying but electrochemical reactions in a variety of SCF media, e.g., water, ammonia, acetonitrile, carbon dioxide, and sulfur dioxide have been proposed. See e.g., A. Bard, Pure & Appl. Chem., 64, 185 (1992), U. Leffrang, et al., Sep. Sci. and Tech., 32, 447 (1997), R.M. Crooks et al., J. Am. Chem. Soc, 106, 6851

(1984), A.C. McDonald et al., J. Phys. Chem., 90, 196 (1986), W.M. Flarsheim et al., J. Phys. Chem. 90, 3857 (1986), R.M. Crooks et al., J. Phys. Chem., 91, 1274 (1987), C.R. Cabrera et al., J. EIectroanal. Chem. 273, 147 (1989), C.R. Cabrera et al., J. Electroanal. Chem., 260, 457 (1989), and C-Y Liu et al., J. Phys. Chem. , 101 , 1180 (1997). Relatively little attention has focused on using SCFs for electrochemical reactions. R. A. Dombro et al., J. Electrochem. Soc, 135, 2219 (1988) and J. Li and G. Prentice, J. Electrochem. Soc, 144, 4284 (1997) propose using an SCF as a media in which to perform electrosynthesis, RΛ.Dombro et al., J. Electrochem. Soc, 135, 2219 (1988) and carbonylation reactions, A.P.Tomilov, Elektrokhimiya, 30, 725 (1994), V.M.Mazin et al., J F/ι/oπ/7e CΛem., 88, 29 (1998) . In contrast, various other studies have focused on employing SCFs as the solvents in electrochemical detectors as the effluent of an HPLC column See e.g., A.C. Michael et al., Anal. Chem., 61, 270 (1989), A.C. Michael et al., Anal. Chem., 61, 2193 (1989), D.E. Niehaus et al., Anal. Chem. 63, 1782 (1991), E.F. Sullenberger et al., Anal. Chem., 65, 2304 (1993), S.A. Olsen et al., Anal. Chem., 66, 503 (1994), and A.P. Abort et al., J. Phys. Chem. 101,

1180 (1997).

Notwithstanding any potential advantages, carrying out electrochemistry in supercritical carbon dioxide is hampered by potential limitations due to the relatively low dielectric constant of the carbon dioxide.

As a result, the dissociation of a salt present therein and hence ionic conductivity is low. Various techniques have been proposed to increase the ionic conductivity. As an example, it has been proposed to employ more polar fluids in the carbon dioxide, e.g., water or methanol. See e.g., A.C. Michael et al., Anal. Chem., 61, 270 (1989), A.C. Michael et al., Anal. Chem:, 61, 2193

(1989), and J. Li and G. Prentice, J. Electrochem. Soc, 144, 4284 (1997).

Such techniques are generally disadvantageous in that they often adversely affect the solution critical point.

There remains a need in the art for increasing the ionic conductivity of carbon dioxide-containing solutions.

Summary of the Invention In one aspect, the invention provides a composition of matter comprising an ionic compound; and a carbon dioxide containing fluid having at least one salt dissolved therein comprising at least one C0₂-phi!ic segment. The carbon dioxide containing fluid displays a higher ionic conductivity relative to a carbon dioxide containing fluid that does not contain the at least one salt.

In another aspect, the invention provides a process which utilizes the composition of matter described herein. In another aspect, the invention provides a method for increasing the ionic conductivity of a carbon dioxide-containing fluid. The method comprises introducing a salt into the carbon dioxide-containing fluid such that the salt dissolves therein to increase the ionic conductivity of the carbon dioxide- containing fluid dissolved therein. The salt comprises at least one CO₂-philic segment. These and other aspects and advantages of the invention are described herein..

Brief Description of the Drawings FIG. 1 A is a schematic diagram illustrating an example of an apparatus

^• that may be used in accordance with the invention.

FIG. 1B is a schematic diagram illustrating an example of an electrode which may be employed in conjunction with the invention.

FIG. 2 is a schematic diagram of a high pressure vessel that can be used in accordance with the invention.

FIGS. 3A-3C are graphs illustrating the effects of pressure, temperature, and types of salt on conductivity of mixtures comprising 5 mmol of: (a) LiCF₃C0₂ (FIG. 3A), (b) NaCF₃CO₂ (FIG. 3B), and (c) KCF₃CO₂ (FIG. 3C). FIGS.4A-4C are graphs illustrating the effects of pressure, temperature, and types of salt on conductivity of mixtures comprising 0.5 mmol of: (a) LiCF₃CO₂ (FIG. 4A), (b) NaCF₃CO₂ (FIG. 4B), and (c) KCF₃CO₂ (FIG. 4C).

FIGS. 5A-5C are graphs illustrating the effects of pressure, temperature, and types of salt on conductivity of mixtures comprising 0.05 mmol of: (a) LiCF₃CO₂ (FIG. 5A), (b) NaCF₃CO₂ (FIG. 5B), and (c) KCF₃CO₂ (FIG. 5C).

FIGS. 6A-6B are graphs illustrating the effects of temperature on the conductivity of mixtures comprising 0.5 mmol of salt. FIG. 6A illustrates the effect of temperature vs. conductivity. FIG. 6B illustrates the effect of temperature vs. pressure.

FIGS. 7A-7B are graphs illustrating the effects of temperature on the conductivity of mixtures comprising 0.05 mmol of salt. FIG. 7A illustrates the effect of temperature vs. conductivity. FIG. 7B illustrates the effect of temperature vs. pressure; FIG. 8 is a graph illustrating the temperature dependence of the molar conductivity for mixtures comprising 0.05 mmol and 0.5 mmol of perfluorinated salts.

FIG. 9 is a graph illustrating the conductivities of mixtures comprising 5 mmol of lithium trifluoroacetate and lithium acetate at each temperature as a function of C0₂ pressure.

FIG. 10 is a graph illustrating the conductivities of mixtures comprising 0.05 mmol of lithium trifluoroacetate and lithium acetate at each temperature as a function of CO₂ pressure.

Detailed Description of the Preferred Embodiments The present invention now will be described more fully hereinafter with reference to the accompanying specification, drawings, and examples, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

In one aspect, the invention relates to a composition of matter. The composition of matter comprises an ionic compound and a carbon dioxide containing fluid having at least salt dissolved therein. The salt comprises at least one CO₂-philic segment, and thus is soluble in the carbon dioxide. The carbon dioxide containing fluid displays a higher ionic conductivity relative to a carbon dioxide containing fluid that does not contain the at least one salt. Preferably, the composition of matter is homogeneous (i.e., single-phase). Any number of ionic compounds may be used for the purposes of the invention. The cations that can be employed are numerous and known to those skilled in the art. Exemplary cations include, without limitation, a metal cation, particularly those which are alkali metals (e.g., sodium, lithium, potassium), alkaline earth metals, transition metals, rare earth metals, and mixtures thereof. Exemplary anions include, without limitation, halogens, hydroxyl, carbonate, phosphate, acetate, trifluoroacetate, and the like. In a preferred embodiment, the composition of matter preferably comprises from about 0.1 , 0.5, 1, or 3 to about 6, 8, 9, or 10 percent by weight of the ionic compound.

For the purposes of the invention, carbon dioxide is employed as a fluid in a liquid or supercritical phase. If liquid CO₂ is used, the temperature employed during the process is preferably below 31 °C. In one embodiment, the CO₂ is utilized in a "supercritical" phase. As used herein, "supercritical" means that a fluid medium is above its critical temperature and pressure, i.e., about 31 °C and about 71 bar for CO₂. The thermodynamic properties of CO₂ . are reported in Hyatt, J. Org. Chem. 49: 5097-5101 (1984); therein, it is stated that the critical temperature of CO₂ is about 31 °C; thus the present invention may be carried out at a temperature above 31 °C. For the purposes of the invention, it is preferred to employ CO₂ at a pressure ranging from about 70 to about 1000 bar.

For the purposes of the invention, the term "CO₂-philic" segment refers to the segment having an affinity or capable of being solubilized in carbon dioxide. Various CO₂-philic segments may be employed including fluorinated segments (e.g., fluorinated polyethers, fluoroalkyls, and fluorinated polyacrylates), perfluorinated segments, silicon-containing segments (e.g., siloxanes), and mixtures thereof. Examples include, but are not limited to, those set forth in U.S. Patent Nos. 5,676,705; and 5,683,977 to Jureller et al., the disclosures of which are incorporated herein by reference in their entirety. In one embodiment, a vast number of perfluorinated salts can be used for the purposes of the invention which contain C0₂-philic segments and which are soluble in the carbon dioxide. The term "perfluorinated salt" refers to one which has at least one perfluorinated group. Examples of perfluorinated salts include, without limitation, a perfluoro alkyl sulfonate, a perfluoro alkyl carboxylate, a perfluoro sulfonyl imide, a perfluoro methide, and mixtures thereof. Exemplary perfluoro alkyl sulfonates are of the formula:

F₃C-(CF₂)n-SO₃M

wherein n ranges from 1 to 10 and M is a cation with a +1 charge including, without limitation, those described herein.

Exemplary perfluoro alkyl carboxylates are of the formula:

F₃C-(CF₂)_n-COOM

Exemplary perfluoro imides are of the formula:

Exemplary perfluoro methides are of the formula:

(F₃C-(CF₂)n-Sθ₂)₃CM

wherein n ranges from and M is a cation including, without limitation, those described herein. In a preferred embodiment, the composition of matter comprises from about 0.1 to about 10 percent by weight of the perfluorinated salt.

In various embodiments, the composition of matter also may optionally comprise at least one co-solvent. A number of co-solvents can be used, and preferably co-solvents which have a dielectric constant greater than supercritical state of carbon dioxide. In a preferred embodiment, polar co- solvents are used. Exemplary co-solvents that could be used include, but are not limited to, alcohols (e.g., methanol, ethanol, and isopropanol); water; nitriles (e.g., acetonitrile); fluorinated and other haiogenated solvents (e.g., chlorotrifluoromethane, trichlorofluoromethane, perfluoropropane, chlorodifluoromethane, and sulfur hexafluoride); amines (e.g., N-methyl pyrrolidone); amides (e.g., dimethyl acetamide); esters (e.g., ethyl acetate, dibasic esters, and lactate esters); ethers (e.g., diethyl ether, tetrahydrofuran, and glycol ethers); ketones (e.g., acetone and methyl ethyl ketone); organosilicones; alkyl pyrrolidones (e.g., N-methyl pyrrolidone); and carbonates(e.g., ethylene carbonate), along with petroleum-based solvents and solvent mixtures, Mixtures of_. the above co-solvents may be used.

If used, the composition of matter preferably comprises from about 5 to about 20 percent by weight of co-solvent.

In various embodiments, the composition of matter of the invention may optionally include a surfactant. Examples of surfactants that can be used include, without limitation, neutral surfactants, ionic surfactants, as well as surfactants that contain at least one "Cθ₂-philic" segment. Preferred surfactants include those containing at least one fluorinated segment (e.g., fluorinated or perfluorinated surfactants). The surfactants which are employed are known to those skilled in the art. Examples of suitable surfactants are set forth in U.S. Patent Nos. 5,783,082; 5,589,105; 5,639,836; and 5,451 ,633 to DeSimone et al_; 5,676,705; and 5,683,977 to Jureller et al., the disclosures of which are incorporated herein by reference in their entirety. Exemplary CO₂-philic segments may include a halogen (e.g., fluoro or chloro)-containing segment, a siloxane-containing segment, a branched polyalkylene oxide segment, or mixtures thereof. Examples of "CO₂-philic" segments are set forth in U.S. Patent Nos. 5,676,705; and 5,683,977 to Jureller et al. If employed, the fluorine-containing segment is typically a "fluoropolymer". As used herein, a "flϋoropolymer" has its conventional meaning in the art and should also be understood to include low molecular weight oligomers, i.e., those which have a degree of polymerization greater than or equal to two. See generally Banks et al., Organofluorine Compounds: Principals and Applications (1994); see also Fluorine-Containing Polymers, 7 Encyclopedia of Polymer Science and Engineering 256 (H. Mark et al. Eds. 2d Ed. 1985). Exemplary fluoropolymers are formed from monomers which may include fluoroacrylate monomers such as 2-(N-ethylperfiuorooctane- sulfonamido) ethyl acrylate ("EtFOSEA"), 2-(N-ethylperfluorooctane- sulfonamido) ethyl methacryiate ("EtFOSEMA"), 2-(N-methylperfluorooctane- sulfonamido) ethyl acrylate ("MeFOSEA"), 2-(N-methylperfluorooctane- sulfonamido) ethyl methacryiate ("MeFOSEMA"), 1,1'-dihydroperfluorooctyl acrylate ("FOA"), 1,1'-dihydroperfluorooctyl methacryiate ("FOMA"), Λ ,22- tetrahydroperfluoroalkylacrylate, ,1 ',2,2'-tetrahydroperfluoroalkyl- methacrylate and other fluoromethacrylates; fluorostyrene monomers such as α-fluorostyrene and 2,4,6-trifluoromethylstyrene; fluoroalkylene oxide monomers such as hexafluoropropylene oxide and perfluorocyclohexane oxide; fluoroolefins such as tetrafluoroethylene, vinylidine fluoride, and chlorotrifluoroethylene; and fluorinated alkyl vinyl ether monomers such as perfluoro(propyl vinyl ether) and perfIuoro(methyl vinyl ether). Copolymers using the above monomers may also be employed. Exemplary siloxane- containing segments include alkyl, fluoroalkyl, and chloroalkyl siloxanes. More specifically, dimethyl siloxanes and polydimethylsiloxane materials are useful. Mixtures of any of the above may be used. In certain embodiments, the "CO₂-philic" segment may be covalently linked to the "C0₂-phobic" segment.

Surfactants that are suitable for the invention may be in the form of, for example, homo, random, block (e.g., di-block, tri-block, or multi-block), blocky (those from step growth polymerization), and star homopolymers, copolymers, and co-oligomers. Exemplary homopolymers include, but are not limited to, poly(1 ,1'-dihydroperfluorooctyl acrylate) ("PFOA"), poly(1.1'-dihydro- perfluorooctyl methacryiate) ("PFOMA"), poly(2-(N-ethylperfluorooctane- sulfonamido) ethyl methacryiate) ("PEtFOSEMA"), and poly(2-(N- ethylperfiuorooctane sulfonamido) ethyl acrylate) ("PEtFOSEA"). Exemplary block copolymers include, but are not limited to^', polystyrene-b-poly(1 ,1- dihydroperfluorooctyl acrylate), polymethyl methacryiate-b-poly(1,1- dihydroperfluorooctyl methacryiate), poly(2-(dimethylamino)ethyl methacrylate)-b-po!y(1,1 -dihydroperfluorooctyl methacryiate), and a diblock copolymer of poly(2-hydroxyethyl methacryiate) and poiy(1,1- dihydroperfluorooctyl methacryiate). Statistical copolymers of poly(1 , 1 - dihydroperfluoro octyl acrylate) and polystyrene, along with poly(1,1- dihydroperfluorooctyl methacryiate) and poly(2-hydroxyethyl methacryiate) can also be used. Graft copolymers may be also be used and include, for example, poly(styrene-g-dimethylsiloxane), poly(methyl acrylate-g- 1,1'dihydroperfluorooctyl methacryiate), and poly(1 ,1 '-dihydroperfluorooctyl acrylate-g-styrene). Random copolymers may be employed and examples of such include, but are not limited to, copolymers or terpolymers of tetrafluoroethylene, vinylidene fluoride, hexafluoropropylene, chlorotrifluoroethylene, and ethylene. Other examples can be found in I. Piirma, Polymeric Surfactants (Marcel Dekker 1992); and G. Odian,

Principals of Polymerization (John Wiley and Sons, Inc. 1991). It should be emphasized that non-polymeric molecules may be used such as perfluoro octanoic acid, surfynols, perfluoro(2-propoxy propanoic) acid, fluorinated alcohols and diols, along with various fluorinated acids, ethoxylates, amides, glycosides, alkanolamides, quaternary ammonium salts, amine oxides, and amines. Mixtures of any of the above may be used.

Various nonionic surfactants optionally can be used in the invention. Examples of nonionic surfactants that can be used include, without limitation, those which are from the family of alkylphenoxypoly(ethyleneoxy)ethanols. Examples of anionic surfactants that may be employed include, but are not limited to, those that are selected from the broad class of sulfonates, sulfates, ethersulfates, sulfosuccinates, diphenyloxide disulfonates, and the like, as well as others that are apparent to one skilled in the art. Cationic surfactants that can be used are numerous and include, without limitation, those which employ cationic moieties include quaternary ammonium, protonated ammonium, sulfonium, and phosphonium moieties. In one embodiment, the surfactants can be used in conjunction with the salt having the CO -philic segment and co-solvent such that micelles are formed which are rich in co-solvent and salt in a homogeneous carbon dioxide-rich phase. Preferably, the compositioi of matter in such an embodiment comprises from about 0.001 , 0.005, 0.01 , or 0.02 to about 0.06, 0.08, or 0.1 percent by weight of surfactant. Alternatively, in another embodiment, the surfactants may be used to form bicontinuous co-solvent- rich and carbon dioxide-rich phases, with the predominant ionic pathway believed to be occurring in the co-solvent-rich phase. For the purposes of the invention, the term "bicontinuous phase" may be defined as a sample- spanning, intertwined arrangement of a co-solvent rich phase and a carbon dioxide rich phase stabilized by surfactant regions, i.e., an emulsion (e.g., microemulsion) which is continuous in the two phase system. In this embodiment, the composition preferably comprises from about 0.001. 0.005, 0.01, or 0.02 to about 0.06, 0.08, or 0.1 percent by weight of surfactant. In forming bicontinuous phases, preferred surfactants include, without limitation, those listed herein (e.g., fluorinated surfactants). Particularly preferred surfactants include perfluoropolyether carboxylates such as those derived from the fluoroalkylene oxide class. Various amounts of surfactant may be used for the purposes of the invention. Preferably, the composition of matter comprises from about 0.001. 0.005, 0.01 , or 0.02 to about 0.06, 0.08, or 0.1 percent by weight of surfactant.

In accordance with the addition, the composition of matter preferably has an ionic conductivity which ranges from about 10^"6, 10^'5, or 10^"4 S/cm to about 10^"3, 10^'2, or 10^'1 S/cm. The. composition of matter preferably displays increased ionic conductivity relative to a composition of matter that does not employ a salt that includes a Cθ₂-philic segment.

In another aspect, the invention provides a process which utilizes the composition of matter as defined herein. Such processes include those which encompass electrochemical aspects. Exemplary processes include, without limitation, an electroorganic synthesis, a waste destruction, a separation, a surface modification, an electrodeposition, an electrodissolution, and an in- situ generation of initiator.

In another aspect, the invention relates to a method of increasing the ionic conductivity of a carbon dioxide-containing fluid. The method comprises introducing a salt into the carbon dioxide-containing fluid such that the - salt dissolves therein and increases the ionic conductivity of the carbon dioxide-containing fluid. In accordance with the invention, the salt is comprises at least one CO₂-philic segment. The method of the invention may encompass, but is not limited tb, any of embodiments set forth hereinabove. The invention may be carried out in various high pressure cells or vessels, including those which are batch, semi-continuous, or continuous. The cell or vessel may optionally be subject to mechanical agitation by employing appropriate devices (e.g., a paddle stirrer or impeller stirrer). When necessary, the cell or vessel may use appropriate heating devices (e.g., a heating furnace or heating rods).

The invention will now be described in greater detail with respect to the examples. It should be understood that the examples are for the purposes of illustration, and in no way limit the invention that is described by the claims.

I. Reagents

In the examples, bone-dry carbon dioxide (National Welders of Raleigh, NC, 99.8 percent, 860 psia) was used as the CO source without further treatment. HPLC grade methanol (Fischer Scientific of Atlanta, Georgia) was used as a co-solvent. The ionic compounds that were studied include lithium trifluoroacetate (95 percent), sodium trifluoroacetate (98 percent), and potassium trifluoroacetate (98 percent) all supplied by the Aldrich Chemical Company of Milwaukee, Wisconsin. To examine the effect of perfluorinated versus non-perfluorinated anion on ionic conductivity, lithium acetate (99.9 percent) furnished by Sigma of Milwaukee, Wisconsin was used. A 1 M solution of each salt in methanol was used as stock solution. Since the salts are generally considered hygroscopic, salt weighing was conducted in an argon-filled glove box. The solution was kept in a septum-sealed bottle to minimize humidity infiltration. Water content of the methanol + salt solutions varied between 150 ppm and 1000 ppm, as measured by Karl-Fisher titration. The measurements were believed to depend on the salt concentration. - ^{" '}

II. High Pressure Vessel

FIG. 1A is a schematic of the apparatus used in the experiments. Carbon dioxide is pumped into the cell using a manually operated pressure generator (model 62-1-10 made available from the High Pressure Equipment Co. of Erie, Pennsylvania. A cylindrical high-pressure vessel was constructed from 316 stainless steel (see FIG. 2). The vessel has five taper-sealed ports on the cylindrical surface, and threaded fixtures on the flat surfaces. The electrodes were mounted on a 316 stainless steel plug using insulated electrical feedthroughs (see FIG. 1B), and the plug was held against a teflon gasket by a threaded thrust ring. In order to observe the phase behavior during the runs, a sapphire window (1-inchdiameter, 3/8-inch thickness, I NSACO) was secured to the opposite face of the vessel by a threaded retainer and a Teflon seal. The volume of electrolyte within the cell was 22 ± 0.5 cm³. Heating tape (Omega of Stamford, Connecticut) was wrapped around the vessel and the temperature was controlled using a thermocouple (T-type) positioned in front of the platinum (Pt) flag and a temperature controller (Omega, CN 76000 series). The five 1/ 6-inch diameter taper- sealed ports were used for sample injection, thermocouple, fluid inlet/outlet, pressure gauge (Omega, PX 615 series with DP 25 series meter), and rupture disk.

III. Electrodes and Instruments

Pt flag electrodes (5 x 5 mm²) were spot welded to a Pt wire (0.02-inch diameter) that served as the electrical lead. The Pt wire was threaded through teflon tubing which, in turn, was placed in a 1/16 stainless steel tube that was put through the stainless steel plug and fixed in place by a taper seal (FIG. 1B and FIG. 2). Each electrode was sealed at the wetted end by Torr Seal® made available by Varian of Palo Alto, California, and when assembled the working and counter electrodes were approximately parallel and positioned 1 cm apart. The cell constant for conductivity calculations was measured as 1.53 cm using a KCI standard solution. Impedance measurements were made with a BAS Zahner IM6e Impedance Analyzer. Most of the measurements were performed in a frequency range of 500 mHz to 1MHz and a 200 mV to 1000 mV amplitude.

IV. Procedure

The cell was filled with CO₂ prior to loading at approximately 800 psig and vented to atmospheric pressure three times. Thereafter, 5 mL of the salt + methanol stock solution was injected into the cell through a syringe, and the injection port was plugged. Carbon dioxide was added to the cell so that an "initial-fill condition" of 17 ± 1 °C and 760 ± 20 psig was obtained. After heating to the desired temperature, the pressure was increased by adding carbon dioxide through the pump while keeping the temperature constant. Sufficient time was allowed to reach equilibrium before recording a measurement. At the conclusion of each measurement, the mixture was vented, the cell was cooled to room temperature, rinsed with methanol several times, and heated to 100°C for 30 minutes while continuously purging with CO₂. The clean and dried cell was stored open to the atmosphere until used in the next set of experiments.

Example 1

Ionic Conductivity of LiCF₃CO₂ in Carbon Dioxide

The ionic conductivity of mixture containing 5 mmol of LiCF₃CO₂ was investigated in carbon dioxide according to the procedure set forth above at various temperatures and pressures. The results are illustrated in FIG. 3A. Example 2

Ionic Conductivity of aCF₃C0₂ in Carbon Dioxide

The procedure according to Example 1 was repeated except that NaCF₃CO2 was investigated. The results are illustrated in FIG. 3B.

Example 3

Ionic Conductivity of KCF₃C0₂ in Carbon Dioxide The procedure according to Example 1 was repeated except that

KCF3CO₂ was investigated. The results are illustrated in FIG. 3C.

Example 4

Ionic Conductivity of LiCF3C0₂ in Carbon Dioxide

The ionic conductivity of mixture containing 0.5 mmol of UCF₃CO₂ was investigated in carbon dioxide according to the procedure set forth above at various temperatures and pressures. The results are illustrated in FIG.4A.

Example 5

Ionic Conductivity of NaCF₃C0₂ in Carbon Dioxide

The procedure according to Example 4 was repeated except that

NaCF₃C0₂ was investigated. The results are illustrated in FIG.4B.

Example 6

Ionic Conductivity of KCF₃C0₂ in Carbon Dioxide

The procedure according to Example 4 was repeated except that KCF₃CO₂ was investigated. The results are illustrated in FIG. 4C. Example 7

Ionic Conductivity of LiCF₃CO₂ in Carbon Dioxide

The ionic conductivity of mixture containing 0.05 mmol of LiCF₃CO₂ was investigated in carbon dioxide according to the procedure set forth above at various temperatures and pressures. The results are illustrated in FIG. 5A.

Example 8

Ionic Conductivity of NaCF₃CO₂ in Carbon Dioxide

The procedure according to Example 7 was repeated except that

NaCF₃CO₂,was investigated. The results are illustrated in FIG. 5B.

Example 9

Ionic Conductivity of KCF₃CO₂ in Carbon Dioxide

The procedure according to Example 7 was repeated except that

KCF₃CO₂ was investigated. The results are illustrated in FIG. 5C.

Example 10

Ionic Conductivities of LiCF₃CO_2j NaCF₃CO_2j and KCF₃C0₂ in Carbon Dioxide

The ionic conductivities of various CO₂ mixtures containing UCF3CO2, NaCF₃CO₂, and KCF3CO₂ were investigated. FIGS. 6A and 6B illustrate the conductivity results for mixtures containing 0.5 mmol of salt at various temperatures and pressures. In general, the lithium salt displayed the highest conductivity. Example 11

Ionic Conductivities of LiCF₃CO₂, NaCF₃CO_2j and KCF₃CO₂ in Carbon Dioxide

The ionic conductivities of various CO₂ mixtures containing LiCF₃CO₂, NaCF₃CO₂, and KCF₃C0₂were investigated. FIGS.7A and 7B illustrate the conductivity results for mixtures containing 0.05 mmol of salt at various temperatures and pressures. In general, the lithium salt displayed the highest conductivity.

Example 12

Ionic Conductivities of LiCF₃CO_2j NaCF₃CO₂, and KCF₃CO₂ in Carbon Dioxide

FIG. 8 illustrate the conductivity results for the salts illustrated in

Examples 10 and 11 listed as a function of temperature. In general, the lithium salt having a concentration of 0.05 mmol displayed the highest conductivity range. Although not intending to be bound by theory, the 0.05 mmol concentration is believed to display a higher conductivity relative to the

0.5 mmol concentration due the fluid being present as a single-phase.

Example 13

Ionic Conductivities of LiCF₃C0₂ and LiCH₃CO₂ in Carbon Dioxide

The ionic conductivities of LiCF₃CO₂and LiCH₃Cθ₂were investigated at various temperatures and pressures in carbon dioxide. The concentration for each salt was 5 mmol. The results are illustrated in FIG. 9. As can be seen, LiCH₃C0₂ displayed higher conductivity values at lower CO₂ pressures whilb UCF3CO₂ displayed higher conductivity values at higher CO₂ pressures. Example 14

Ionic Conductivities of LiCF₃CO₂ and LiCH₃CO₂ in Carbon Dioxide

The ionic conductivities of LiCF₃CO₂and LiCH₃C0₂were investigated at various temperatures and pressures in carbon dioxide. The concentration for each salt was 0.05 mmol. The results are illustrated in FIG. 10. As can be seen, UCF3CO₂ generally displayed higher conductivity values throughout the

CO₂ pressure range than UCH3CO₂.

The invention is illustrated by reference to the above embodiments. It should be appreciated however that the invention is not limited to these embodiments but is instead defined by the. claims that follow.

Claims

THAT WHICH IS CLAIMED:

1. A composition of matter comprising: an ionic compound; and a carbon dioxide containing fluid having at least one salt dissolved therein comprising at least one CO₂-philic segment, wherein the carbon dioxide containing fluid displays a higher ionic conductivity relative to a carbon dioxide containing fluid that does not contain the at least one salt.

2. The composition of matter according to Claim 1 , wherein the carbon dioxide is supercritical carbon dioxide.

3. The composition of matter according to Claim 1 , wherein the carbon dioxide is liquid carbon dioxide.

4. The composition of matter according to Claim 1 , wherein the at least one CO₂-philic segment is a perfluorinated group.

5. The composition of matter according to Claim 1 , wherein the at least one CO₂-philic segment is a siloxane group.

6. The composition of matter according to Claim 1 , wherein the salt is selected from the group consisting of a perfluoro alkyl sulfonate, a perfluoro alkyl carboxylate, a perfluoro sulfonyl imide, a perfluoro methide, and mixtures thereof.

7. The composition of matter according to Claim 1 , wherein said composition further comprises a co-solvent.

8. The composition of matter according to Claim 7, wherein the co- solvent has a dielectric constant that is greater than carbon dioxide.

9. The composition of matter according to Claim 8, wherein the co- solvent is selected from the group consisting of water, a nitrile, an alcohol, a carbonate, and mixtures thereof.

10. The composition of matter according to Claim 1 , wherein the ionic compound comprises a metal selected from the group consisting of an alkali metal, an alkaline earth metal, a rare earth metal, a transition metal, and mixtures thereof.

1.1. The composition of matter according to Claim 10, wherein the ionic compound comprises sodium, lithium, potassium, and mixtures thereof.

12. The composition of matter according to Claim 7, wherein said composition further comprises a surfactant.

13. The composition of matter according to Claim 12, wherein the surfactant comprises a fluorinated segment.

14. The composition of matter according to Claim 13, wherein the fluorinated segment comprises at least one monomer selected from the group consisting of a fluoroacrylate, a fluorinated methacryiate monomer, a fluorostyrene, a fluoroalkylene oxide, a fluoroolefin, a fluorinated alkyl vinyl ether, and mixtures thereof.

15. The composition of matter according to Claim 13, wherein the fluorinated segment comprises at least one monomer selected from the group consisting of 2-(N-ethylperfluorooctane- sulfonamido) ethyl acrylate, 2-(N- ethylperfluorooctane- sulfonamido) ethyl methacryiate, 2-(N-methyl perfluorooctane- sulfonamido) ethyl acrylate, 2-(N-methylperfluorooctane- sulfonamido) ethyl methacryiate, 1 ,T-dihydroρerfluorooctyl acrylate, 1,1'- dihydroperfluorooctyl methacryiate, 1 ,1 ',2,2'-tetrahydroperfluoroalkylacrylate, l.l'^^'-tetrahydroperfluoroalkyl- methacryiate, -fluorostyrene, 2,4,6- trifluoromethylstyrene, hexafluoropropylene oxide, perfluorocyclohexane oxide, tetrafluoroethylene, vinylidine fluoride, chlorotrifluoroethylene, perfluoro(propyl vinyl ether), perfluoro(methyl vinyl ether), and mixtures thereof.

16. The composition of matter according to Claim 12, wherein said composition of matter comprises a co-solvent rich phase and carbon dioxide- rich phase and wherein the phases, are bicontinuous.

17. The composition of matter according to Claim 16, wherein the surfactant is a perfluoropolyether carboxylate.

18. The composition of matter according to Claim 1 , wherein the ionic conductivity of the composition of matter ranges from about 10^"6 S/cm to about 10^"1 S/cm.

19. A process which utilizes the composition of matter as recited in Claim 1.

20. The process according to Claim 19, wherein said process is selected from the group consisting of an electroorganic synthesis, a waste destruction, a separation, a surface modification, an electrodeposition, an electrσdissolution and an in-situ generation of initiator.

21. A method for increasing the ionic conductivity of a carbon dioxide-containing fluid, said method comprising: introducing a salt into the carbon dioxide-containing fluid such that the salt dissolves therein to increase the ionic conductivity of the carbon dioxide- containing fluid dissolved therein, the salt comprising at least one C0₂-philic segment.

22. The method according to Claim 21 , wherein the carbon dioxide is supercritical carbon dioxide.

23. The method according to Claim 21 , wherein the carbon dioxide is liquid carbon dioxide.

24. The method according to Claim 21 , wherein the at least one CO₂-philic segment is a perfluorinated group.

25. The method according to Claim 21 , wherein the at least one CO₂-philic segment is a siloxane group.

26. The method according to Claim 21 , wherein the salt is selected from the group consisting of a perfluoro alkyl sulfonate, a perfluoro alkyl carboxylate, a perfluoro sulfonyl imide, a perfluoro methide, and mixtures thereof.

27. The method according to Claim 21 , wherein said carbon dioxide-containing fluid further comprises a co-solvent.

28. The method according to Claim 27, wherein the co-solvent has a dielectric constant that is greater than carbon dioxide.

29. The method according to Claim 27, wherein the co-solvent is selected from the group consisting of water, a nitrile, an alcohol, a carbonate, and mixtures thereof.

30. The method according to Claim 21 , wherein the ionic compound comprises a metal selected from the group consisting of an alkali metal, an alkaline earth metal, a transition metal, a rare earth metal, and mixtures thereof.

31. The method according to Claim 31 , wherein the ionic compound comprises sodium, lithium, potassium, and mixtures thereof.

32. The method according to Claim 27, wherein said carbon dioxide-containing fluid further comprises a surfactant.

33. The method according to Claim 32, wherein the surfactant comprises a fluorinated segment.

34. The method according to Claim 33, wherein the fluorinated segment comprises at least one monomer selected from the group consisting of a fluoroacrylate, a fluorinated methacryiate monomer, a fluorostyrene, a fluoroalkylene oxide, a fluoroolefin, a fluorinated alkyl vinyl ether, and mixtures thereof.

35. The method according to Claim 33, wherein the fluorinated segment comprises at least one monomer selected from the group consisting of 2-(N-ethylperfluorooctane- sulfonamido) ethyl acrylate, 2-(N- ethylperfluorooctane- sulfonamido) ethyl methacryiate, 2-(N-methyl perfluorooctane- sulfonamido) ethyl acrylate, 2-(N-methyiperfluorooctane- sulfonamido) ethyl methacryiate, 1,1 '-dihydroperfluorooctyl acrylate, 1,1'- dihydfoperfluorooctyl methacryiate, 1 ,1 ',2,2'-tetrahydroperfluoroalkylacrylate, 1,1',2,2'-tetrahydroperfluoroalkyl methacryiate, α-fluorostyrene, 2,4,6- trifluoromethylstyrene, hexafluoropropylene oxide, perfluorocyclohexane oxide, tetrafluoroethylene, vinylidine fluoride, chlorotrifluoroethylene, perfluoro ropyl vinyl ether), perfluoro(methyl vinyl ether), and mixtures thereof.

36. The method according to Claim 32, wherein said composition of matter comprises a co-solvent rich phase and carbon dioxide-rich phase and wherein the phases are bicontinuous.

37. The method according to Claim 36, wherein the surfactant is a perfluoropolyether carboxylate.