Tadeusz Hofman

Measurements and Molecular Interactions for N,N-Dimethylformamide with Ionic Liquid Mixed Solvents

To understand the molecular interactions between N,N-dimethylformamide (DMF) with two families of ionic liquids (ILs), we have measured thermophysical properties such as densities (rho) and ultrasonic sound velocities (u) over the whole composition range at 25 degrees C under atmospheric pressure. The excess molar volume (V(E)) and the deviation in isentropic compressibilities (DeltaK(s)) were predicted using these properties as a function of the concentration of IL. These results are fitted to the Redlich-Kister polynomials. The materials investigated in the present study included two families of ILs such as ammonium salts and imidazolium salts. Diethylammonium acetate ([Et(2)NH][CH(3)COO], DEAA), triethylammonium actetate ([Et(3)NH][CH(3)COO], TEAA), triethylammonium dihydrogen phosphate ([Et(3)NH][H(2)PO(4)], TEAP), and triethylammonium sulfate ([Et(3)NH][HSO(4)], TEAS) are ammonium salts and 1-benzyl-3-methylimidazolium chloride ([Bmim][Cl]) belongs to the imidazolium family. The intermolecular interactions and structural effects were analyzed on the basis of the measured and the derived properties. A qualitative analysis of the results is discussed in terms of the ion-dipole, ion-pair interactions, and hydrogen bonding between ILs and DMF molecules and their structural factors.

Temperature dependence measurements and structural characterization of trimethyl ammonium ionic liquids with a highly polar solvent.

We report the synthesis and characterization of a series of an ammonium ionic liquids (ILs) containing acetate, dihydrogen phosphate, and hydrogen sulfate anions with a common cation. To characterize the thermophysical properties of these newly synthesized ILs with the highly polar solvent N,N-dimethylformamide (DMF), precise measurements such as densities (ρ) and ultrasonic sound velocities (u) over the whole composition range have been performed at atmospheric pressure and over wide temperature ranges (25-50 °C). The excess molar volume (V(E)) and the deviation in isentropic compressibilities (Δκ(s)) were predicted using these temperature dependence properties as a function of the concentration of ILs. The Redlich-Kister polynomial was used to correlate the results. The ILs investigated in the present study included trimethylammonium acetate [(CH(3))(3)NH][CH(3)COO] (TMAA), trimethylammonium dihydrogen phosphate [(CH(3))(3)NH][H(2)PO(4)] (TMAP), and trimethylammonium hydrogen sulfate [(CH(3))(3)NH][HSO(4)] (TMAS). The intermolecular interactions and structural effects were analyzed on the basis of the measured and the derived properties. In addition, the hydrogen bonding between ILs and DMF has been demonstrated using semiempirical calculations with help of Hyperchem 7. A qualitative analysis of the results is discussed in terms of the ion-dipole, ion-pair interactions, and hydrogen bonding between ILs and DMF molecules and their structural factors. The influence of the anion of the protic IL, namely, acetate (CH(3)COO), dihydrogen phosphate (H(2)PO(4)), and hydrogen sulfate (HSO(4)), on the thermophysical properties is also provided.

Influence of alkyl chain length and temperature on thermophysical properties of ammonium-based ionic liquids with molecular solvent.

Mixing of ionic liquids (ILs) with molecular solvent can expand the range of structural properties and the scope of molecular interactions between the molecules of the solvents. Exploiting of these phenomena essentially require a basic fundamental understanding of mixing behavior of ILs with molecular solvents. In this context, a series of protic ILs possessing tetra-alkyl ammonium cation [R(4)N](+) with commonly used anion hydroxide [OH](-) were synthesized and characterized by temperature dependent thermophysical properties. The ILs [R(4)N](+)[OH](-) are varying only in the length of alkyl chain (R is methyl, ethyl, propyl, or butyl) of tetra-alkyl ammonium on the cationic part. The ILs used for the present study included tetramethyl ammonium hydroxide [(CH(3))(4)N](+)[OH](-) (TMAH), tetraethyl ammonium hydroxide [(C(2)H(5))(4)N](+)[OH](-) (TEAH), tetrapropyl ammonium hydroxide [(C(3)H(7))(4)N](+)[OH](-) (TPAH) and tetrabutyl ammonium hydroxide [(C(4)H(9))(4)N](+)[OH](-) (TBAH). The alkyl chain length effect has been analyzed by precise measurements such as densities (ρ), ultrasonic sound velocity (u), and viscosity (η) of these ILs with polar solvent, N-methyl-2-pyrrolidone (NMP), over the full composition range as a function of temperature. The excess molar volume (V(E)), the deviation in isentropic compressibility (Δκ(s)) and deviation in viscosity (Δη) were predicted using these properties as a function of the concentration of ILs. Redlich-Kister polynomial was used to correlate the results. A qualitative analysis of the results is discussed in terms of the ion-dipole, ion-pair interactions, and hydrogen bonding between ILs and NMP molecules. Later, the hydrogen bonding features between ILs and NMP were also analyzed using a molecular modeling program with the help of HyperChem 7.

Densities, Excess Volumes, Isobaric Expansivities, and Isothermal Compressibilities of the 1-Ethyl-3-methylimidazolium Ethylsulfate + Ethanol System at Temperatures (283.15 to 343.15) K and Pressures from (0.1 to 35) MPa

Densities of pure 1-ethyl-3-methylimidazolium ethylsulfate ionic liquid, [C 2 mim][EtSO 4 ], and its mixtures with ethanol have been measured with an accuracy of ± 0.2 kg·m ―3 , over the temperature range of (283.15 to 343.15) K and pressure range of (0.1 to 35) MPa, using a vibrating tube densimeter. The experimental densities have been correlated by the Tait equation with the temperature-dependent parameters (for the pure ionic liquid) and by a van Laar type equation, involving parameters dependent on temperature and pressure (for the mixtures). Excess volumes have been derived directly from the experimental densities, and isobaric expansivities, isothermal compressibilities, and related excess properties have been calculated with the use of the correlation equation. The exceptionally strong influence of pressure and temperature on these properties has been confirmed.

Solubility and vapour pressures in saturated solutions of high-molecular-weight hydrocarbons

Abstract Solubilities of C 18 , C 19 , C 20 n-paraffins (octadecane, nonadecane and eicosane) in 15 solvents have been measured over a wide range of temperature. Vapour—liquid equilibrium along the saturation line for the octadecane-cyclohexane system has also been determined. The solubility data of heptadecane, octadecane, nonadecane and eicosane have been described by five two-parameter correlation equations, namely the Redlich—Kister, van Laar and three versions of the Wilson equation and by the so calle λ h -equation. The root mean square deviations of the solubility temperatures for all measured data vary from 1.2 to 4.6 K and depend on the particular equation used. The poorer description was obtained from the solubility data in the literature for heptadecane.

Thermodynamics of association of pure alcohols

Abstract The relations for the standard entropy and enthalpy of successive association are deduced from the theory of polycondensation. With their values calculated from the enthalpies of vaporization and the absolute entropies of the liquid state of pure compounds, the new model is applied to describe spectroscopic properties of ethanol up to the critical temperature proving its superiority over the other association models.

Properties of pure alkanes, ethers and their mixtures by a hole model group-contribution equation of state

Abstract The abilities of the Smirnova–Victorov [N.A. Smirnova, A.I. Victorov, Fluid Phase Equilibria 34 (1987) 235–263] group-contribution equation of state to predict properties of pure normal alkanes, unbranched monoethers and binary systems containing these compounds, have been tested. The properties include, for pure compounds: orthobaric densities, enthalpies of vaporization, pρT properties of gases and liquids, saturated vapor pressures, isothermal compressibilities, thermal expansion coefficients, and for mixtures: excess enthalpies, volumes and heat capacities, vapor–liquid equilibria at low and high pressures, solid–liquid equilibria, infinite dilution activity coefficients. The required parameters have been derived from a limited number of data and without help of an optimization technique. It was found that the temperature dependence of the energetic parameters proposed in the original Smirnova–Victorov formulation did not give a significant improvement over an approach in which this dependence is totally neglected. As a result, only one energetic parameter was used instead of three. Generally fairly good prediction was obtained, although temperature dependencies are worse reproduced. The results have been compared with those obtained by the Nitta–Chao group-contribution equation of state [T. Nitta, E.A. Turek, R.A. Greenkorn, K.C. Chao, AIChEJ. 23 (1977) 144–160].

Solubility of long-chain n-alkanols in dipropyl and dibutyl ether

Solubility of the following 1-alkanols (1-dodecanol, 1-tridecanol, 1-tetradecanol, 1-pentadecanol, 1-hexadecanol and 1-octadecanol) in dipropyl ether or dibutyl ether are reported. They have been measured by the dynamic method from a temperature close to 0°C up to the melting point. All systems exhibit positive deviations from ideal solubility. For all the alcohols, two transition points close to the melting temperature have been observed. The abilities of the Modified UNIFAC (Dortmund) and the DISQUAC models to predict these data have been tested.

Application of the extended real associated solution model to predict thermodynamic properties of n-alcohol + linear monoether mixtures

Abstract Applicability of the extended real associated solution (ERAS) model to describe and predict properties of n-alcohol + unbranched monoether mixtures has been tested. Two versions of the model have been applied: its original, developed by Heintz [1] and a modified form, reported recently by Hofman and Casanova [2]. The basic assumption states that the purely physical contribution to the model should be meaningless. The model has three adjustable parameters which are common for all the mixtures considered. It has been applied to predict HE, VE and VLE data. The modified version gives acceptable results which for the non-volume properties are similar to those predicted by the Modified UNIFAC (Dortmund) using six parameters. The original ERAS model turned out to be inadequate.

Determination of stability constants of complexes from the titration curve by the maximum likelihood principle

The numerical methods used to determine stability constants from titration data are analysed. A new method based on the maximum likelihood principle is proposed.