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A study to examine the solubility of gases in ionic liquids (ILs) is conducted. Findings reveal a several fold increase in carbon dioxide solubility due to the use of fluoro-alkyl chains.

The ability of C[O.sub.2] to induce liquid/liquid-phase separation in mixtures of ionic liquids and organics is examined. The ability of C[O.sub.2] to act as an antisolvent has depended on the solubility of the C[O.sub.2] in the ionic liquid/organic mixture and strong hydrogen bonding between the ionic liquid and the organic has made it difficult for C[O.sub.2] to induce a liquid/liquid-phase secarbon compoundsparation.

The solvent strength of IL/organic mixtures is reported using Reichardt's dyes 30 and 33, Kamlet-Taft parameters and phenol blue. The results shows that the polarity of ILs is largely unaffected by the organic consolvent that is the probes are preferentially solvated by the ILs.

A report on the solubilities of a variety of gases in several different ionic liquids is presented. It is concluded that the nature of the anion has the most significant influence on the gas solubilities.

The influence of anion, cation alkyl chain length, and additional alkyl substituents on the cation ring and on the solubility of CO2 in ILs at pressures to 150 bar is investigated. The results suggest that the solubility of carbon dioxide is strongly dependent on the choice of anion.

The bimolecular rate constants of the addition reaction between hydroxyl radical and nitrobenzene are determined in subcritical and supercritical water (SCW) at temperatures between ambient and 390 degree celsius. The measured bimolecular rate constants reported distinctly non-Arrhenius behavior from ambient to 350 degree celsius but increased in the slightly subcritical and supercritical region between 350 and 390 degree celsius.

A study of the ability of subcritical water to support ionic chemistry from the successful generation of (-R-xanthenium (R = H and C6H5) carbocations at temperatures up to 330 degrees Celsius from their respective alcohol precursors. The results show that for ion/neutral isoCoulombic reactions, require low-temperature Arrhenius parameters to predict the rate constants in water at higher temperatures and that the effect of pressure on the bimolecular rate constants in the temperature range of 22-330 degrees Celsius was negligible.

A study investigated the triplet-triplet annihilation of anthracene in supercritical water at temperatures ranging from 375 degrees to 450 degrees C and pressures of 50-350 bar. The experiment aimed to determine whether the conclusions about diffusion-controlled reactions in lower temperature supercritical fluids also apply to reactions in supercritical water. Observed rate constant and anthracene triplet extinction coefficient data were taken to determine the bimolecular rate constants as a function of temperature and pressure.

Investigation of local solvation effects during fluorescence quenching of anthracene in supercritical CO2 as the reaction is varied from diffusion controlled to kinetically controlled found that reaction rates depend on donor energy levels and acceptor electron affinities. Results indicate that a large pressure effect is exerted on reaction rate by local composition enhancement of the quencher molecules in the anthracene solute. Fluorescence spectra and solvatochromic shift data indicate both local density augmentation and local composition increases around the anthracene.

The absolute reactivity of triplet benzophenone and benzyl free radicals towards molecular oxygen in supercritical CO2 and CHF3 is measured using laser flash photolysis, absolute reaction kinetics and integral equation theory in order to investigate preferential consolvent solvation in ternary supercritical fluid mixtures. The bimolecular rate constants increase slightly with increase in pressure and are consistent with the preferential solvation of the solute.

Investigations of the possibility of diffusion-controlled mechanisms being obstructed or enhanced in supercritical fluids or fluid mixtures, draw on the findings of the triplet-triplet annihilation process of benzophenone (Ph2C double bond O) and the self-termination reaction of benzyl radical, PhCh2. Both reactions occur basically at the diffusion-control limit in supercritical fluoroform and carbon dioxide doped with 1 mol % acetonitrile when spin statistical factors are considered.

A study was done on the effects of pressure on the absolute kinetics of benzophenone photoreduction in supercritical CO2. Results show that the highest rate constants occur at lower pessures near the critical point of the solution despite the decrease in activation volume during lowering to the critical pressure. These findings show the effects of increasing the local concentration of substrate in the compressible region near the critical point.

Amino acid ionic liquid trihexyl(tetradecyl)phosphonium methioninate [[P.sub.66614][Met] and prolinate [[P.sub.66614][Pro] has absorbed C[O.sub.2] in nearly 1:1 stoichiometry. Density functional theory calculations have supported the 1:1 reaction stoichiometry and have predicted reaction enthalpies with calorimetric measurements isotherms.

The examination of C[O.sub.2] solubility in a number of ionic liquids with systematic increases in fluorination reveals that ionic liquids containing increased fluoroalkyl chains on either the cation or anion improve C[O.sub.2] solubility when compared to less fluorinated ionic liquids.

The effect of chemical and structural factors on the phase behavior of ionic liquids with alcohols is examined, focusing on pyridinium ionic liquids (ILs) for comparison to imidazolium ILs from previous studies. The nonrandom two-liquid (NRTL) equation with binary interaction parameters with linear temperature dependence has provided a good fit of the experimental data for all the systems.

The effect of chemical and structural factors on the phase behavior of ionic liquids with alcohols is examined, focusing on pyridinium ionic liquids (ILs) for comparison to imidazolium ILs from previous studies. The nonrandom two-liquid (NRTL) equation with binary interaction parameters with linear temperature dependence has provided a good fit of the experimental data for all the systems.

Byline: Jennifer L. Anthony, Sudhir N.V.K. Aki, Edward J. Maginn, Joan F. Brennecke Ionic liquids (ILs) are organic salts that are liquids in their pure state at ambient conditions. They are frequently referred to as 'environmentally benign' due to their immeasurably low vapour pressure. In addition to their more widely studied capabilities as solvents for reactions, several ionic liquids also show potential in other environmentally conscious applications, such as in the capture of CO2. In previous gas solubility studies with the ionic liquids 1-n-butyl-3-methylimidazolium hexafluorophosphate, [bmim][PF6], and 1-n-butyl-3-methylimidazolium tetrafluoroborate, [bmim][BF4] [1,2], we have found that CO2 has a much higher solubility in these ILs than many other gases, including N2, O2, and CH4. Here we show experimental measurements using a static absorber that confirm that [bmim][PF6] can be used to remove CO2 from a gas mixture containing either N2 or CH4. We also compare capture of CO2 using ILs to conventional technology using monoethanolamine (MEA).

The mechanisms for the high solubility of CO2 in imidazolium-based ionic liquids are investigated with the help of experimental and molecular modeling studies. The findings indicate that the association of CO2 with the anion is the best indicator of CO2 solubility in alkylimidazolium-based ionic liquids.

The impact of different characteristics of the ionic liquids (ILs) and the alcohols on the liquid-liquid phase equilibrium of imidazolium-based ionic liquids and alcohols is examined. The ionic liquid-water mutual solubility data for a number of ionic liquids is discussed.

The measurements of the hydrogen abstraction from methanol by hydroxyl radical in water at temperatures from ambient to 390 degree C and at 250 bar is presented. The experimental rate constants for hydrogen abstraction from methanol to hydroxyl radical are significantly higher than the values used by a variety of researchers who have attempted to model oxidation of methanol in supercritical water using detailed chemical kinetics models.

The solubility of nine different gases in 1-n-butyl-3-methylimidazolium hexafluorophosphate namely carbon dioxide, ethylene, ethane, methane, argon, oxygen, carbon monoxide, hydrogen and nitrogen are presented. The result suggests that the mass transfer of gases into ionic liquids is important for reactions involving in these gases and it is determined that ionic liquids show good potential for use as a gas-separation medium.

The high-pressure phase behavior of CO2 with six ionic liquids and the effect of systematically changing the anionic and cationic components of the ionic liquid on the CO2-ionic liquid phase behavior are studied. The result tries to explain the physical mechanism of the unusual phase behavior and also indicates the existence of the correlation between CO2 solubility and liquid molar volume.

Chemists have always been intrigued by the usefulness of ionic liquids at room temperatures especially since they are used as solvents for extractions and reactions but separation of these liquids from organic and inorganic species is a difficult task. Experiments were conducted to use carbon dioxide to separate ionic liquids from their compounds.

It is been found that non-valatile organic compounds can be taken from ionic liquids using supercritical carbon dioxide. The carbon dioxide dissolves in the liquid, but the ionic liquid does not dissolve in carbon dioxide. The ionic liquid 1-butyl-3-methylimidazolium hexafluorphosphate (BMIM) (PF6) was synthesized, with the aim of showing that CO(sub2) could be used to extract naphthalene.

Several studies have been carried out to analyze the reactions of probes of molecular structure and its influence on reactivity in supercritical fluids. A number of these studies have examined the homogeneous reactions of organic compounds to determine the effects of solvent structure. Results indicated that primary effects on reaction rates, selectivities and mechanisms can be differentiated. In addition, solvent shells do not support their integrity long enough to generate cage effects in the decomposition process.

New research that shows the use of a fluorinated dendrimer to extract hydrophilic compounds from water into liquid carbon dioxide (CO2) could considerably expand the use of CO2 as a solvent. Such 'smart' CO2 agents can extend CO2's ability as a solvent and could replace chlorinated liquids in cleaning operations. Other uses could include the extraction of pharmaceutical products from fermentation broths. Details of the study are presented.