Theses and dissertations (Applied Sciences)
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Item Thermodynamic properties of phosphonium-based ionic liquid mixtures at different temperatures(2018) Kabane, Bakusele; Redhi, Gan G.Ionic Liquids (ILs) are relatively newly formed types of solvents. As part of ongoing research, research groups and industries are focusing on solvents classified as ionic liquids, which have a low melting point,and they have been given great attention focusing on their thermophysical properties and applications. In order to utilize or industrially exploit these types of solvents, the understanding of intermolecular interactions and properties of pure liquids and their mixtures is important. Thermophysical properties of ionic liquid mixtures, especially density, viscosity and speed of sound are measured as a function of temperature. Accurate analysis on thermophysical properties of ionic liquids is more of paramount interest as they indicate the transformation of ionic liquids from small laboratory level to large-scale industrial implementation.In this study, new data for the binary mixtures containing {trihexyltetradecylphosphonium chloride ([P+14, 6, 6, 6] [Cl-]) IL and propanoic acid (PA)} and {1-ethyl-3-methylimidazolium tetrafluoroborate ([Emim][BF4]) + benzaldehyde or ethyl acetoacetate} were investigated under atmospheric pressure (p equivalent to 0.1 MPa) and at temperatures (293.15 to 313.15) K. Densities (ρ),viscosities (𝜂) as well as speeds of sound (𝑢)were measured over the whole range of mole fraction (𝑥𝑖= 0 to 1). The computed excess properties which includes excess molar volumes(𝑉mE), apparent molar volume (𝑉𝜙),intermolecular free length (Lf), isentropic compressibility(𝑘𝑠), deviations in viscosity (Δ𝜂), apparent molar isentropic compressibility (𝐾𝜙) and deviation in isentropic compressibility(Δ𝑘𝑠)were computed from the experimentally determined data of densities, viscosities and speeds of sound. In addition, measurements of activity coefficients at infinite dilution forvolatile organic compounds (alkenes, alcohols, alkanes, cycloalkanes, aromatic hydrocarbons, thiophene, ketones, acetonitrile, water and tetrahydrofuran) in the IL [trihexyltetradecylphosphonium-bis-(2, 4,4-trimethylpentyl)-phosphinate and trihexyltetradecylphosphonium chloride] were conducted at different temperatures.The obtained results and derived properties have been elucidated in terms of the interactions taking place among the solvent systems.Item Thermophysical properties of biofuel components derived from biomass(2016) Nduli, Mbalenhle B.; Deenadayalu, NirmalaThe thermophysical properties of the binary mixtures containing biofuel components derived from biomass were determined. Experimental densities, speed of sound, and refractive indices for the binary mixtures (methanol or 1-ethyl-3-methylimidazolium acetate [EMIM][OAc] + furfural or furfuryl alcohol ) were measured at T = (298.15, 303.15, 308.15, 313.15 and 318.15) K. From the experimental data, excess molar volume, E m V , isentropic compressibility, s , molar refractions, R, and deviation in refractive index, Δn, were calculated. The excess molar volumes were found to be negative for all systems studied. The isentropic compressibility were found to be both positive for the whole composition and temperature range and increases slightly with increasing temperature. The deviation in refractive index was positive over the whole composition range. The obtained values of excess molar volumes and changes of refractive index on mixing were satisfactorily correlated by the Redlich–Kister equation. The Lorentz–Lorenz equation was applied to predict the density and calculate the excess molar volume of the binary mixtures.