Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

ABSTRACT

By using the isothermal saturation method, the solid-liquid equilibrium of 2-nitro-p-phenylenediamine in pure organic solvents of methanol, ethanol, n-propanol, isopropanol, N-methyl-2-pyrrolidone, acetonitrile, ethyl acetate, toluene and 1,4-dioxane and liquid mixture of (N-methyl-2-pyrrolidone + methanol) was obtained experimentally at the temperatures ranging from (283.15 to 318.15) K under atmospheric pressure, and the solubility of 2-nitro-p-phenylenediamine in the selected solvents was determined by a high-performance liquid chromatography (HPLC). Within the studied temperature range, the 2-nitro-p-phenylenediamine solubility in mole fraction in these solvents increased with increasing temperature. The descending order of the mole fraction solubility in pure solvents was as follow: (N-methyl-2-pyrrolidone, 1,4-dioxane) greater than ethyl acetate greater than acetonitrile greater than methanol greater than ethanol greater than n-propanol greater than isopropanol greater than toluene, and for the (N-methyl-2-pyrrolidone + methanol) mixture with given initial composition, the mole fraction solubility of 2-nitro-p-phenylenediamine increased with increasing temperature and mass fraction of N-methyl-2-pyrrolidone. The values of solubility for 2-nitro-pphenylenediamine in pure solvent were correlated and calculated with the modified Apelblat equation, kh equation, Wilson model and NRTL model; and in the binary solvent mixture of (N-methyl-2- pyrrolidone + methanol), the Jouyban Acree model, modified Apelblat Jouyban Acree model and Sun model. For the pure solvents, the largest values of the relative average deviation (RAD) and root-meansquare deviation (RMSD) obtained by the four models were 1.17% and 6.80*10-4, respectively; and for (N-methyl-2-pyrrolidone + methanol) mixture, they were a larger, which were 3.59% and 19.12*10-4. In general, the selected thermodynamic models were all acceptable for describing the solubility behaviour of 2-nitro-p-phenylenediamine in the solvents. In addition, the mixing properties including the mixing Gibbs energy, mixing enthalpy, mixing entropy, activity coefficient at infinitesimal concentration (c1 1 ) and reduced excess enthalpy (HE;1 1 ) were calculated for 2-nitro-p-phenylenediamine in pure solvents. Knowledge of the solubility and thermodynamic studies is essential in optimizing the purification process of 2-nitro-p-phenylenediamine.