Joseph W. Magee

The distillation and volatility of ionic liquids

It is widely believed that a defining characteristic of ionic liquids (or low-temperature molten salts) is that they exert no measurable vapour pressure, and hence cannot be distilled. Here we demonstrate that this is unfounded, and that many ionic liquids can be distilled at low pressure without decomposition. Ionic liquids represent matter solely composed of ions, and so are perceived as non-volatile substances. During the last decade, interest in the field of ionic liquids has burgeoned, producing a wealth of intellectual and technological challenges and opportunities for the production of new chemical and extractive processes, fuel cells and batteries, and new composite materials. Much of this potential is underpinned by their presumed involatility. This characteristic, however, can severely restrict the attainability of high purity levels for ionic liquids (when they contain poorly volatile components) in recycling schemes, as well as excluding their use in gas-phase processes. We anticipate that our demonstration that some selected families of commonly used aprotic ionic liquids can be distilled at 200–300 °C and low pressure, with concomitant recovery of significant amounts of pure substance, will permit these currently excluded applications to be realized.

Thermodynamic and thermophysical properties of the reference ionic liquid: 1-Hexyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]amide (including mixtures). Part 2. Critical evaluation and recommended property values (IUPAC Technical Report)

This article is a product of IUPAC Project 2002-005-1-100 (Thermodynamics of ionic liquids, ionic liquid mixtures, and the development of standardized systems). Experimental results of thermodynamic, transport, and phase equilibrium studies made on a reference sample of the ionic liquid 1-hexyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]amide are summarized, compared, and critically evaluated to provide recommended values with uncertainties for the properties measured. Properties measured included thermal properties (triple-point temperature, glass-transition temperature, enthalpy of fusion, heat capacities of condensed states), volumetric properties, speeds of sound, viscosities, electrolytic conductivities, relative permittivities, as well as properties for mixtures, such as gas solubilities (solubility pressures), solute activity coefficients at infinite dilution, and liquid-liquid equilibrium temperatures. Recommended values with uncertainties are provided for the properties studied experimentally. The effect of the presence of water on the property values is discussed.

Thermodynamic and thermophysical properties of the reference ionic liquid: 1-Hexyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]amide (including mixtures). Part 1. Experimental methods and results (IUPAC Technical Report)

This article summarizes the results of IUPAC Project 2002-005-1-100 (Thermodynamics of ionic liquids, ionic liquid mixtures, and the development of standardized systems). The methods used by the various contributors to measure the thermophysical and phase equilibrium properties of the reference sample of the ionic liquid 1-hexyl-3-methylimidazolium bis [(trifluoromethyl)sulfonyl]amide and its mixtures are summarized along with the uncertainties estimated by the contributors. Some results not previously published are presented. Properties of the pure ionic liquid included thermal properties (triple-point temperature, glass-transition temperature, enthalpy of fusion, heat capacities of condensed states), volumetric properties, speeds of sound, viscosities, electrolytic conductivities, and relative permittivities. Properties for mixtures included gas solubilities, solute activity coefficients at infinite dilution, liquid-liquid equilibrium temperatures, and excess volumes. The companion article (Part 2) provides a critical evaluation of the data and recommended values with estimated combined expanded uncertainties.

The effect of dissolved water on the viscosities of hydrophobic room-temperature ionic liquids

Data for viscosity vs. water content for three hydrophobic room-temperature ionic liquids show that their viscosities are strongly dependent on the amount of dissolved water.

Isochoric (p, v, T) measurements on CO2 and (0.98 CO2+0.02 CH4) from 225 to 400 K and pressures to 35 MPa

Comprehensive isochoric (p, v, T) measurements have been obtained for (0.98 CO2+0.02 CH4) at densities from 1 to 26mol·dm−3. Supplemental isochoric (p, v, T) measurements have been obtained for high-purity CO2 at densities from 12 to 24 mol·dm−3. Measurements of p(T) cover a broad range of temperature, 225 to 400 K, at pressures to 35 MPa. Comparisons have been made with independent sources and with a predictive method based on corresponding states.

Isochoricp-ϱ-T measurements on Difluoromethane (R32) from 142 to 396 K and pentafluoroethane (R125) from 178 to 398 K at pressures to 35 MPa

Thep-ϱ-T-relationships were measured for difluoromethane (R32) and pentafluoroethane (R125) by an isochoric method with gravimetric determinations of the amount of substance. Temperatures ranged from 142 to 396 K for R32 and from 178 to 398 K for R125, while pressures were up to 35 MPa. Measurements were conducted on compressed liquid samples. Determinations of vapor pressures were made for each substance. I have used vapor pressure data and thep-ϱ-T data to estimate saturated liquid densities by extrapolating each isochore to the vapor pressure, and determining the temperature and density at the intersection. Publishedp-ϱ-T data are in good agreement with this study. For thep ϱ T apparatus. the uncertainty of the temperature is ±0.03 K. and for pressure it is ±0.01%, atp > 3 MPa and ±0.05% atp < 3 MPa. The principal source of uncertainty is the cell volume (28.5193 cm3 at 0 K and 0 M Pa), which has a standard uncertainty of ±0.003 cm3. When all components of experimental uncertainty are considered. the expanded uncertainty (at the two-sigma level) of the density measurements is estimated to be 0.05%.

PVT relationships in a carbon dioxide-rich mixture with ethane

Comprehensive isochoric PVT measurements have been obtained for the system (0.99 CO2 + 0.01 C2H6). The range of state points studied includes those with densities from 2 to 24 mol·dm−3, temperatures from 245 to 400 K, and pressures to 35 MPa. Extensive comparisons have been made with two predictive conformai solution models, one which uses the 32-term BWR-type equation of Stewart and Jacobsen as a reference and the other using the newer Schmidt-Wagner functional form. Results obtained with the Schmidt-Wagner equation are better in the near-critical region owing to the flatter critical isotherm associated with this functional form.

Specific heats (Cv) of saturated and compressed liquid and vapor carbon dioxide

Specific heats of saturated liquid carbon dioxide (Csat) have been measured in the temperature range 220 to 303 K. Specific heats at constant volume (Cv) have been measured at 12 densities ranging from 0.2 to 2.5 times the critical density in the temperature range 233 to 330 K, with pressures varying from 3.4 to 32 MPa. The measurements have been conducted in an adiabatic constant-volume calorimeter of conventional design. Uncertainty of the specific heats is estimated to not exceed 2.0%. Comparisons are made with an extended Benedict-Webb-Rubin equation of state and with the results of other workers.

ThermoData Engine (TDE): software implementation of the dynamic data evaluation concept. 8. Properties of material streams and solvent design.

ThermoData Engine (TDE) is the first full-scale software implementation of the dynamic data evaluation concept, as reported in this journal. The present paper describes the first application of this concept to the evaluation of thermophysical properties for material streams involving any number of chemical components with assessment of uncertainties. The method involves construction of Redlich-Kister type equations for individual properties (excess volume, thermal conductivity, viscosity, surface tension, and excess enthalpy) and activity-coefficient models for phase equilibrium properties (vapor-liquid equilibrium). Multicomponent models are based on those for the pure-components and all binary subsystems evaluated on demand through the TDE software algorithms. Models are described in detail, and extensions to the class structure of the program are provided. Novel program features, such as ready identification of key measurements for subsystems that can reduce the combined uncertainty for a particular stream property, are described. In addition, new product-design features are described for selection of solvents for optimized crystal dissolution, separation of binary crystal mixtures, and solute extraction from a single-component solvent. Planned future developments are summarized.

Molar heat capacity at constant volume of difluoromethane (R32) and pentafluoroethane (R125) from the triple-point temperature to 345 K at pressures to 35 MPa

Molar heat capacities at constant volume (Cv) of dill uoromethane (R32) and pentalluoroethane (R125) were measured with an adiabatic calorimeter. Temperatures ranged from their triple points to 345 K, and pressures up to 35 MPa. Measurements were conducted on the liquid in equilibrium with its vapor and on compressed liquid samples. The samples were of a high purity, verified by chemical analysis of each fluid. For the samples, calorimetric results were obtained for two-phase (Cv(2)), saturated liquid (Cσ orC′x), and singlephase (Cv) molar heat capacities. TheCσ data were used to estimate vapor pressures for values less than 0.3 MPa by applying a thermodynamic relationship between the saturated liquid heat capacity and the temperature derivatives of the vapor pressure. The triple-point temperature (Ttr) and the enthalpy of fusion (ΔfusH) were also measured for each substance. The principal sources of uncertainty are the temperature rise measurement and the change-ofvolume work adjustment. The expanded uncertainty (at the two-sigma level) forCv is estimated to be 0.7%, forCv(2) it is 0.5%, and forCσ it is 0.7%.