Fundamental Research On Crystallization Separation Of Dichloronitrobenzene Isomers

3,4-Dichloronitrobenzene(3,4-DCNB) and2,3-dichloronitrobenzene(2,3-DCNB) are both important intermediate in organic synthesis which can be further synthesis of many compounds and are widely used in the synthesis of pharmaceutical and pesticides. When producing3,4-DCNB, the isomer2,3-DCNB is generated. Because3,4-DCNB and2,3-DCNB are close to boiling point, it is hard to effectively separation by common distillation. In the process of purifying3,4-DCNB by melt crystallization, a large number of low temperature eutectic is formed. Crystallization with solvent is a practical method to separate the two isomers. The solubility and density have important significance on separation of3,4-DCNB and2,3-DCNB by crystallization with solvent. But understanding of the properties of3,4-DCNB and2,3-DCNB are absent.The solubility of3,4-DCNB and2,3-DCNB in methanol+water, ethanol+water,1-propanol,2-propanol,1-butanol, ethyl actetate, tetrahloromethane, cyclohexane, hexane and heptane were measured with temperature range from T=(278.15to303.15) K. The solubility of3,4-DCNB and2,3-DCNB in binary mixed solvents increased with both increasing in temperature and mass fraction of methanol or ethanol. The solubility of3,4-DCNB and2,3-DCNB in pure solvents increased with increasing in temperature. The solubility of3,4-DCNB is higher than that of2,3-DCNB in different solvents at constant temperature and concentration. The solubility data are correlated by the Apelblat equation, Vant Hoff equation, A.h equation, Wlison equation and NRTL equation in different solvent, the parameters of equations and it’s corresponding RMSD were obtained. The fitting precision of Apelblat equation is better than these of Vant Hoff equation, λh equation, Wlison equation and NRTL equation, the Apelblat equation is more suitable for the correlation the solubility of system than others. In addition, the solubility of3,4-DCNB and2,3-DCNB with respect to both temperature and solvent composition in methanol+water, ethanol+water were correlated by Jouyban-Acree equation, Jouyban-Acree Apelblat equation and Jouyban-Acree Vant Hoff equation, the parameters of equations and it’s corresponding RMSD were obtained. The Jouyban-Acree equation is suitable for the correlation the solubility with respect to both temperature and solvent composition of3,4-DCNB and2,3-DCNB.The mutual solubility of3,4-DCNB+2,3-DCNB+methanol,3,4-DCNB+2,3-DCNB+ethanol and3,4-DCNB+2,3-DCNB+cyclohexane by Schreinemakers’method, the phase diagrams of these systems were constructed on the basis of the measured solubility. The density of3,4-DCNB and2,3-DCNB in methanol, ethanol,1-propanol,2-propanol,1-butanol, ethyl actetate, cyclohexane, hexane and heptane have been measured from283.15K to333.15K by Pycnometer method. The experimental data are correlated by VTF equation, the parameters of equation and it’s corresponding standard deviation are obtained, the largest standard deviation less than0.13%. The Vogel-Tamman-Fulcher (VTF) equation is suitable for the correlation the density with the temperature and the concentration. The apparent molar volumes are calculated according to density data of3,4-DCNB and2,3-DCNB in different solvents.