Organic Carbonates as Solvents in Synthesis and Catalysis

This tutorial review outlines current state of the art research on ionic liquid lubricants. Ionic liquids (ILs) were first reported as very promising high-performance lubricants in 2001 and have attracted considerable attention in the field of tribology since then because of their remarkable lubrication and anti-wear capabilities as compared with lubrication oils in general use; in recent times we have seen dramatically increased interest in the topic. The review starts with a brief introduction to ILs and fluid lubrication, and then discusses in more detail the tribological properties of IL lubricants, either as lubrication oils, additives or thin films. As well as lubrication mechanisms, some current problems and potential solutions are tentatively discussed.

Ionic liquid lubricants: designed chemistry for engineering applications

Recent developments in phase change materials for energy storage applications: A review

In a preceding project, functional forms for “short” Helmholtz energy equations of state for typical nonpolar and weakly polar fluids and for typical polar fluids were developed using simultaneous optimization. In this work, the coefficients of these short forms for the equations of state have been fitted for the fluids acetone, carbon monoxide, carbonyl sulfide, decane, hydrogen sulfide, 2-methylbutane (isopentane), 2,2-dimethylpropane (neopentane), 2-methylpentane (isohexane), krypton, nitrous oxide, nonane, sulfur dioxide, toluene, xenon, hexafluoroethane (R-116), 1,1-dichloro-1-fluoroethane (R-141b), 1-chloro-1,1-difluoroethane (R-142b), octafluoropropane (R-218), 1,1,1,3,3-pentafluoropropane (R-245fa), and fluoromethane (R-41). The 12 coefficients of the equations of state were fitted to substance specific data sets. The results show that simultaneously optimized functional forms can be applied to other fluids out of the same class of fluids for which they were optimized without significant loss of a...

Short Fundamental Equations of State for 20 Industrial Fluids

Current research on room-temperature ionic liquids as lubricants is described. Ionic liquids possess excellent properties such as non-volatility, non-flammability, and thermo-oxidative stability. The potential use of ionic liquids as lubricants was first proposed in 2001 and approximately 70 articles pertaining to fundamental research on ionic liquids have been published through May 2009. A large majority of the cations examined in this area are derived from 1,3-dialkylimidazolium, with a higher alkyl group on the imidazolium cation being beneficial for good lubrication, while it reduces the thermo-oxidative stability. Hydrophobic anions provide both good lubricity and significant thermo-oxidative stability. The anions decompose through a tribochemical reaction to generate metal fluoride on the rubbed surface. Additive technology to improve lubricity is also explained. An introduction to tribology as an interdisciplinary field of lubrication is also provided.

Ionic liquids in tribology.

One of the potential applications of the ionic liquids (ILs) is their use as lubricants or lubricant additives. The choice of the cation and the anion of the ILs, as well as the side chain design, determine their fundamental properties, which permits us to create tailor-made lubricants and lubricant additives among other functional fluids. In this work we have studied 10 ILs for which we report densities and viscosities from 283.15 K (and for some ILs at lower temperatures) up to 373.15 K. The viscosities of the ILs fall in the range of the applications of hydraulic fluid or lubricants. Four of these ILs were composed by the anion tris(pentafluoroethyl)trifluorophosphate [(C2F5)3PF3]− and one of the following cations: 1-butyl-2,3-dimethylimidazolium [C4C1C1min]+, 1-butyl-1-methylpyrrolidinium [C4C1Pyrr]+, 1-(2-methoxyethyl)-1-methyl-pyrrolidinium [C1OC2C1Pyrr]+, and trihexyl(tetradecyl)phosphonium [P6,6,6,14]+. Furthermore, three of the ILs contain the anion bis(trifloromethylsulfonyl)imide [NTf2]− and on...

Influence of Molecular Structure on Densities and Viscosities of Several Ionic Liquids

The viscosity and density of four pure liquid compounds (dimethyl carbonate, diethyl carbonate, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether) were measured at several temperatures between 283.15 and 353.15 K. The density measurements were performed up to 60 MPa with an uncertainty of 1×10−4g·cm−3. The viscosity at atmospheric pressure was measured with an Ubbelohde-type glass capillary tube viscometer with an uncertainty of ±1%. At pressures up to 100 MPa the viscosity was determined with a falling ball viscometer with an uncertainty of ±2%. The density (410 experimental values) and viscosity data (184 experimental values) were fitted to several correlation equations.

High-Pressure Measurements of the Viscosity and Density of Two Polyethers and Two Dialkyl Carbonates

New density data for diethyl adipate (DEA) over 12 isotherms [(293.15 ≤ T ≤ 403.15) K] and 15 isobars [(0.1 ≤ p ≤ 140) MPa] are reported. This paper presents also the calibration procedure we propose for a new experimental equipment. Data reliability has been verified over the pressure and temperature experimental intervals by comparing our experimental results for toluene and 1-butanol with previous literature data. A total of 732 experimental data points have been measured in the framework of this work. The experimental uncertainty is estimated to be ± 0.5 kg·m−3 (around 0.05 %). The pressure and temperature dependencies of diethyl adipate densities were accurately represented by the Tammann−Tait equation with standard deviations of 0.3 kg·m−3. These data were used to analyze the isothermal compressibility and the isobaric thermal expansivity for this fluid.

Density of diethyl adipate using a new vibrating tube densimeter from (293.15 to 403.15) K and up to 140 MPa. calibration and measurements

The choice of cation and anion in an ionic liquid (IL) as well as the design of ion side chains determine the fundamental properties of ILs, which permits creating tailor-made lubricants and lubricant additives. So, the study of the influence of molecular structure on thermophysical properties of ionic liquids is essential for their use in lubrication. Recent results from the literature, essentially based on ammonium, phosphonium, or imidazolium cations, are promising from the tribological point of view, but still new investigations should be performed, for example, in elastohydrodynamic lubrication (EHL), for which calculations of the universal pressure–viscosity coefficient, α film , and central thickness are needed. In this work viscosity and density data from the literature on broad pressure and temperature ranges for the ILs [C4C1im]PF6, [C4C1im]Tf2 N, [C4C1im]BF4, [C8C1im]PF6, [C8C1im]BF4, [C6C1im]PF6, and [C6C1im]Tf2 N are used to determine their α film values over a wide temperature range. The American Gear Manufacturers Association relation of the central thickness with the pressure viscosity coefficient is used to estimate the film-generating capability of these lubricants. Furthermore, an overview of the literature data on tribological and physical properties of the ionic liquids is presented.

The Pressure–Viscosity Coefficient of Several Ionic Liquids

Casalini and Roland [Phys. Rev. E 69, 062501 (2004); J. Non-Cryst. Solids 353, 3936 (2007)] and other authors have found that both the dielectric relaxation times and the viscosity, η, of liquids can be expressed solely as functions of the group (TV γ), where T is the temperature, V is the molar volume, and γ a state-independent scaling exponent. Here we report scaling exponents γ, for the viscosities of 46 compounds, including 11 ionic liquids. A generalization of this thermodynamic scaling to other transport properties, namely, the self-diffusion coefficients for ionic and molecular liquids and the electrical conductivity for ionic liquids is examined. Scaling exponents, γ, for the electrical conductivities of six ionic liquids for which viscosity data are available, are found to be quite close to those obtained from viscosities. Using the scaling exponents obtained from viscosities it was possible to correlate molar conductivity over broad ranges of temperature and pressure. However, application of the...

María J. P. Comuñas

Papers

Influence of Molecular Structure on Densities and Viscosities of Several Ionic Liquids

High-Pressure Measurements of the Viscosity and Density of Two Polyethers and Two Dialkyl Carbonates

Density of diethyl adipate using a new vibrating tube densimeter from (293.15 to 403.15) K and up to 140 MPa. calibration and measurements

The Pressure–Viscosity Coefficient of Several Ionic Liquids

Density scaling of the transport properties of molecular and ionic liquids