Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

In this work, five 1,1,3,3-tetramethylguanidine (TMG) based ionic liquids (ILs) having [TMG] cation with monocarboxylic acid as anion {[CH3-(CH2)n.COOH], where n = 2,3, 4, 5 and 6} were synthesized and characterized by 1H-NMR, and 13C-NMR. CO2 absorption capacity was studied for even number carboxylic acid anions [TMG][But], [TMG][Hex] and [TMG][Oct]. The maximum absorption capacity of CO2 was observed for [TMG][Oct], which clearly indicated that the increase in chain length increases the absorption capacity. The physicochemical properties such as density (n), speed of sound (u) viscosity (c) and refractive index (nD) values were measured as a function of temperature over the range from 293.15 K to 343.15 K at atmospheric pressure (0.1 MPa). The experimental density values were fitted with second order polynomial equation and correlated with the expected density proposed by Gardas- Coutinho model. The thermodynamic properties, such as thermal expansion coefficient (a) isentropic compressibility (aS) and free length theory (Lf) were calculated. The strength of ionic interaction between the ions was estimated by calculating lattice potential energy (UPOT) and standard entropy (Sdeg ) from experimental data. The experimental viscosity values were fitted by applying Vogel-Fulcher-Tammann equation and correlated with Arrhenius type equation. Thermal decomposition temperatures (Td) were investigated using TG analysis. The intermolecular interactions of the ILs have been analyzed with the experimental refractive index data at various temperatures and the effects of carboxylate anion chain length and temperature on physicochemical properties were also investigated.