Solubility of 1-methyl-4-nitropyrazole in three binary solvent mixtures from 283.15 K to 323.15 K at 0.1 MPa

Abstract

In order to find a more suitable solvent system, the solubility of 1-methyl-4-nitropyrazole (1-M-4-NP) in three different binary solvents (i.e., water + acetone, water + methanol and water + ethanol) with different mass fraction of water (0.1000, 0.2000, 0.3000, 0.4000, 0.5000, 0.6000 and 0.7000) was firstly determined by a dynamic laser monitoring within a temperature range of 283.15 K to 323.15 K at atmospheric pressure (P = 0.1 MPa). The experimental results indicated that the solubility of 1-M-4-NP in selected binary solvents increases with the increasing temperature, while decreases with the rising water mole fraction ranging. Besides, the results showed that the value of solubility is largest in water + acetone and the value is smallest in water + ethanol when the mole fraction of water and temperature are constant. Therefore, the (solid + liquid) equilibrium values in the studied solvents were correlated based on the modified Apelblat equation, van't Hoff equation, CNIBS/R-K model and Jouyban-Acree model, and the modified Apelblat equation provide a more accurate result of the experimental values than other three models. In addition, the NRTL model was applied to calculate the thermodynamic properties of 1-M-4-NP including mixing enthalpy, mixing entropy and mixing free Gibbs energy in the studied binary solvent mixtures at given temperature, and it's easy to understand that the dissolution is an endothermic process from the results. Furthermore, the experimental solubility values, model parameters and thermodynamic properties of 1-M-4-NP in different mixed solvents will provide necessary support for its preparation, crystallization process and further theoretical studies.