Cyanopyridinium-Based Ionic Liquids and Their Mixtures for Ethylene and Ethane Separation.

The solubility of ethane and ethylene was determined in a series of cyanopyridinium ionic liquids known to form charge-transfer complexes with polyaromatic hydrocarbons to determine their potential to form specific interactions with the unsaturated gas. The solubilities of ethylene and ethane in 1-butyl-4-cyanopyridinium bis-(trifluoromethane)-sulfonimide ([C CNPy]-[NTf]) and 1-butyl-3-cyanopyridinium bis-(trifluoromethane)-sulfonimide ([C CNPy]-[NTf]) were measured using an isochoric saturation method. The mole fraction solubility of ethane in the ionic liquids ranged from 6.

The role of urea in formation of the sodium acetate trihydrate (SAT)-urea eutectic liquid: a neutron diffraction and isotopic substitution study.

Neutron diffraction with isotopic substitution has been used to investigate the structure of the liquid sodium acetate trihydrate-urea eutectic (mole fraction () of 0.60) at 50 °C. Urea competes with acetate anions and water molecules in the solvation of sodium ions, displacing water and, simultaneously, stabilising the liberated 'excess' water through hydrogen bonding between water and urea molecules in the eutectic liquid.

A High-Throughput Experimental Approach to Screening Gas Sorption by Liquids and Solids.

High-precision measurement of gas uptake from single or mixed feeds in solid and liquid sorbents traditionally requires time-consuming experimental procedures and/or complex and costly equipment. A simple and cost-effective headspace gas chromatography (HS-GC) approach for the fast, universal experimental screening of sorbents for gas uptake and/or determination of their real gas separation selectivity has been developed and is demonstrated for pressures up to 2500 mbar and temperatures above 30 °C. This method allows screening of solids and both volatile and nonvolatile liquid materials, physisorbents, and chemisorbents using both single and mixed permanent gases that can include CO, CH, H, and NH, for gas uptakes as low as 0.

The structure of protic ionic liquids based on sulfuric acid, doped with excess of sulfuric acid or with water.

Neutron scattering with isotopic substitution was used to study the structure of concentrated sulfuric acid, and two protic ionic liquids (PILs): a Brønsted-acidic PIL, synthesised using pyridine and excess of sulfuric acid, [Hpy][HSO]·HSO, and a hydrated PIL, in which an equimolar mixture of sulfuric acid and pyridine has been doped with water, [Hpy][HSO]·2HO. Brønsted acidic PILs are excellent solvents/catalysts for esterifications, driving reaction to completion by phase-separating water and ester products. Water-doped PILs are efficient solvents/antisolvents in biomass fractionation.

The synthesis of deuteriated tri-tert-butyl phosphine.

The synthesis of deuteriated tri-tert-butyl phosphine is reported. This synthesis is an adaptation of the known procedure for tri-tert-butyl phosphine via a Grignard intermediate.

Hydrophobic functional liquids based on trioctylphosphine oxide (TOPO) and carboxylic acids.

Trioctylphosphine oxide (TOPO) is a hydrophobic extracting agent used in a number of commercially important separations of valuable solutes from aqueous streams (with examples ranging from lanthanides, through gallium, to carboxylic acids). TOPO is traditionally used as a solute in kerosene, its extraction efficiency limited by its solubility in the organic diluents. In this work, eighteen hydrogen bond donors (HBDs) were screened for their capacity to liquefy TOPO, employing strategies used to design deep eutectic solvents (DES).

Hydration of sulfobetaine dizwitterions as a function of alkyl spacer length.

The solvation and structure of bolaform dizwitterions containing two sulfobetaine moieties in concentrated aqueous solution were determined using neutron diffraction with isotopic substitution (NDIS) combined with modelling of the measured structure factors using Empirical Potential Structure Refinement (EPSR). Strongly directional local hydration was observed in the polar regimes of the dizwitterions with 48-52 water molecules shared between dizwitterion molecules in a first shell water network around each zwitterion pair. Overall, the double zwitterions were highly hydrated, providing experimental evidence in support of the potential formation of protein-resistant hydration layers at zwitterion-water interfaces.

Enhanced extraction of phenol from model oils using ionic liquids elucidated with neutron diffraction.

Aromatic cation ionic liquids (ILs) based on alkylpyridiniums are shown to be good phenol extractants from model oils (hexane/toluene). ILs with hard basic anions are found to have best extraction efficiency consistent with tetraalkylammonium salts ([NR4]X). Key extraction interactions were analysed using small angle neutron diffraction.

Investigation of glycerol hydrogen-bonding networks in choline chloride/glycerol eutectic-forming liquids using neutron diffraction.

The structure of choline chloride/glycerol (ChCl : Gly) mixtures at two mole fractions (the eutectic χChCl = 0.33 (1 : 2), and a higher χChCl = 0.50 (1 : 1) composition) in the liquid state at 333 K and 1 atm.

A comparison of choline:urea and choline:oxalic acid deep eutectic solvents at 338 K.

1:2 choline chloride:urea and 1:1 choline chloride:oxalic acid deep eutectic solvents are compared at 338 K using liquid-phase neutron diffraction with H/D isotopic substitution to obtain differential neutron scattering cross sections and fitting of models to the experimental data using Empirical Potential Structure Refinement. In comparison to the previously reported study of choline chloride:urea at 303 K, we observed significant weakening and lengthening of choline-OH⋯Cl and choline-OH⋯hydrogen-bond acceptor correlations.

Frustrated Lewis pairs in ionic liquids and molecular solvents - a neutron scattering and NMR study of encounter complexes.

The presence of the weakly-associated encounter complex in the model frustrated Lewis pair solution (FLP): tris(tert-butyl)phosphine (P(Bu)) and tris(pentafluorophenyl)borane (BCF) in benzene, was confirmed via PB correlation analysis from neutron scattering data. On average, ca. 5% of dissolved FLP components were in the associated state.

Applying neutron diffraction with isotopic substitution to the structure and proton-transport pathways in protic imidazolium bis{(trifluoromethyl)sulfonyl}imide ionic liquids.

Neutron diffraction with isotopic substitution has been applied to examine the potential for complex-ion formation in protic imidazolium bis{(trifluoromethyl)sulfonyl}imide ionic liquids. Strong cation-anion hydrogen-bonding in the 1 : 1 base : acid ionic liquid results in a high population of anions adopting a cis-conformation and, on adding excess imidazole (2 : 1 base : acid stoichiometry), cation-base and base-base correlations were identified, however, persistent hydrogen-bond associations were not observed.

LCST Phase Behavior and Complexation with Water of an Ionic Liquid Incorporating the 5-Phenyltetrazolate Anion.

The use of 5-phenyltetrazole, a bioisostere of benzoic acid, as an anion source to prepare an ionic liquid is described for the first time. Tetrabutylphosphonium 5-phenyltetrazolate undergoes phase separation from water with lower critical solution temperature phase behavior, in contrast to completely water miscible tetrabutylphosphonium benzoate, and also exhibits strong complexation with water with both eutectic and peritectic behavior that has not previously been observed in ionic liquid+water systems. The anhydrous and trihydrate salts were isolated and characterized by single crystal X-ray diffraction.

Intermolecular structure and hydrogen-bonding in liquid 1,2-propylene carbonate and 1,2-glycerol carbonate determined by neutron scattering.

Neutron diffraction with isotopic substitution has been used to investigate the liquid structures of propylene carbonate and glycerol carbonate. C-HO[double bond, length as m-dash]C hydrogen-bonding motifs dominate the local structure of propylene carbonate, giving rise to the formation of head-to-tail correlated chains of molecules. In contrast, glycerol carbonate exhibits a more disordered structure with no overall dominant interactions in which the pendant hydroxyl function disrupts structure-making correlations present in propylene carbonate.

Mercury capture on a supported chlorocuprate(ii) ionic liquid adsorbent studied using operando synchrotron X-ray absorption spectroscopy.

Mercury scrubbing from gas streams using a supported 1-butyl-3-methylimidazolium chlorocuprate(ii) ionic liquid ([Cmim][CuCl]) has been studied using operando EXAFS. Initial oxidative capture as [HgCl] anions was confirmed, this was then followed by the unanticipated generation of mercury(i) chloride through comproportionation with additional mercury from the gas stream. Combining these two mechanisms leads to net one electron oxidative extraction of mercury from the gas with increased potential capacity and efficiency for supported ionic liquid mercury scrubbers.

Solvation Structure of Uracil in Ionic Liquids.

The local solvation environment of uracil dissolved in the ionic liquid 1-ethyl-3-methylimidazolium acetate has been studied using neutron diffraction techniques. At solvent:solute (ionic liquid:uracil) ratios of 3:1 and 2:1, little perturbation of the ion-ion correlations compared to those of the neat ionic liquid are observed. We find that solvation of the uracil is driven predominantly by the acetate anion of the solvent.

Structure and dynamics of aqueous 2-propanol: a THz-TDS, NMR and neutron diffraction study.

Aqueous liquid mixtures, in particular, those involving amphiphilic species, play an important role in many physical, chemical and biological processes. Of particular interest are alcohol/water mixtures; however, the structural dynamics of such systems are still not fully understood. Herein, a combination of terahertz time-domain spectroscopy (THz-TDS) and NMR relaxation time analysis has been applied to investigate 2-propanol/water mixtures across the entire composition range; while neutron diffraction studies have been carried out at two specific concentrations.

Lewis Superacidic Ionic Liquids with Tricoordinate Borenium Cations.

The first examples of ionic liquids based on borenium cations, [BCl2 L](+), are reported. These compounds form highly Lewis acidic liquids under solvent-free conditions. Their acidity was quantified by determining the Gutmann acceptor number (AN).

An ionic liquid process for mercury removal from natural gas.

Efficient scrubbing of mercury vapour from natural gas streams has been demonstrated both in the laboratory and on an industrial scale, using chlorocuprate(II) ionic liquids impregnated on high surface area porous solid supports, resulting in the effective removal of mercury vapour from natural gas streams. This material has been commercialised for use within the petroleum gas production industry, and has currently been running continuously for three years on a natural gas plant in Malaysia. Here we report on the chemistry underlying this process, and demonstrate the transfer of this technology from gram to ton scale.

Association and liquid structure of pyridine-acetic acid mixtures determined from neutron scattering using a 'free proton' EPSR simulation model.

The liquid structure of pyridine-acetic acid mixtures have been investigated using neutron scattering at various mole fractions of acetic acid, χHOAc = 0.33, 0.50, and 0.

Brønsted acids in ionic liquids: how acidity depends on the liquid structure.

Gutmann Acceptor Number (AN) values have been determined for Brønsted acid-ionic liquid mixtures, over a wide compositional range. Four systems of general formula [C2mim][A]-HA (A(-) = bistriflamide, [NTf2](-); triflate, [OTf](-); mesylate, [OMs](-); or acetate, [OAc](-), [C2mim](+) = 1-ethyl-3-methylimidazolium cation) were studied. A library of Brønsted acidic systems of varying acidity was constructed and the AN parameter was found to be a convenient approach for quantifying their acidity.

Determining relative rates of cellulose dissolution in ionic liquids through in situ viscosity measurement.

Using in situ viscosity measurement, the rate of cellulose dissolution in a number of ionic liquids has been determined allowing their performance as solvents to be quantitatively assessed. 1-Butyl-3-methylimidazolium ethanoate was shown to dissolve cellulose faster than analogous ionic liquids with chloride or dimethylphosphate anions. Analysis of the data highlights the influence of both anion basicity and relative concentration on the rate of dissolution.