The Solubility Of 4-Chlorotoluene And 2,4-Dichlorofluorobenzene In Sub-critical Water With The In-situ Raman Spectroscopy

The solubility of organic compounds is a key attribute which very important for isolation and purification of substance, formulation selection, and industrial applications and processes design in supercritical fluid. Due to increasing concern and widely application of supercritical fluid, the phase equilibria of substance and the significance of solubility in supercritical fluid have been caused the attention of scholars. Due to the experimental conditions of supercritical fluid, it’s very difficult to obtain the accurate solubilities. For traditional static methods, it easily destroyed the phase equilibrium significantly when withdraw a sample from the equilibration cell, however, dynamic methods difficult to guarantee the system achieve true balance, so the solubility of chlorinated organic compounds are lack.A new high-temperature and-pressure optically transparent fused silica capillary reactor(FSCR) system proposed by our group was used to study the solubility of 4-chlorotoluene and 2,4-dichlorofluorobenzene in sub-critical water.We used the supercritical point of ethnol and melting point of sodium nitrate to calibrate the temperature of heating/cooling stage, and study the stability of 4-chlorotoluene and 2,4-dichlorofluorobenzene in sub-critical water. The homogeneity of solute in sub-critical water in FSCR was checked using in-situ Raman spectroscopy. In addition, the Raman spectra of 4-chlorotoluene, solvent(water) and pure water were collected during its process of dissolution with the rise of temperature.The results show 4-chlorotoluene and 2,4-dichlorofluorobenzene didn’t occur oxidation or hydrolysis reaction. The system of solute and water reached equilibrium after a long period of constant temperature. The solubilities of 4-chlorotoluene and 2,4-dichlorofluorobenzene in range of 262.3-293.8 ℃ and 257.6-286.7 ℃ were obtained using the FSCR combined with a microscope recorder system, the results showed that the solubilities of 4-chlorotoluene and 2,4-dichlorofluorobenzene increased linearly with increasing temperature.