Measurement and correlation of solubility of 2-alkylanthraquinone (ethyl, tert-butyl and tert-amyl) in mixed solvents of 1,3,5-trimethylbenzene and tetrabutylurea

The solubility of 2-ethylanthraquinone (EAQ), 2-tert-butylanthraquinone (TBAQ) and 2-tert-amylanthraquinone (TAAQ) in binary solvents consisted of 1,3,5-trimethylbenzen (TMB) and tetrabutylurea (TBU) was measured by the equilibrium method at the temperature ranging between 303.15 and 323.15 K and 101.1±2 kPa. With raising the temperature and content of TMB in the mixed solvents, the solubility of EAQ, TBAQ and TAAQ increased gradually. At the same content of TMB and temperature the solubility of TAAQ was higher than that of TBAQ, which was in its turn much higher than that of EAQ. The experimental data were correlated by Wilson model, NRTL model and modified λ-h equation, respectively. Among them, Wilson model gave a relatively good accuracy with the average and maximum relative deviation of 0.56% and 1.77% for EAQ, 1.08% and 4.58% for TBAQ, 0.65% and 1.78% for TAAQ. In addition, the solubility of TAAQ in TMB + TBU was predicted by Wilson model, NRTL model and modified λ-h equation, respectively. The Wilson model showed the best reliability, with the average and maximum relative deviation of 0.98% and 3.10%. The calculated enthalpy change, entropy change and Gibbs free energy change of the dissolution process for AQs all were positive, which demonstrates the dissolving process to be endothermic, entropy-driving and non-spontaneous.