Study On The Solubilities Of M-chlorotoluene And 1,2-dichlorobenzene In Subcritical Water In Fused Silica Capillary Reactor

The solubility data of hydrophobic organic compounds at ambient temperature and pressure is not valued, because of its characteristic of insolubility or microsolubility. But the solubility of hydrophobic organic compounds in water at high temperature and pressure enhanced significantly even can completely be dissolved with each other under the sub- and supercritical condition where the dielectric constant decreases.As a basic parameter, substance solubility data in sub- and supercritical water is very important for kinetic study of chemical reactions, chemical synthesis, extraction separation, and design, operation and optimization of high temperature and pressure reactor, However, due to the hardness to reach the high temperature and pressure condition, high requirement for equipments and operating difficulty, hydrophobic organic solubility data is still greatly deficient.Currently, methods for measuring solubilities of organic compounds in sub- and supercritical water can be divided into two types: static and dynamic method. The main disadvantage of static method is that when sampling solution from the equilibration cell would cause considerable pressure drop and disturbing the phase equilibrium process. Similarly, the dynamic method also exists shortcomings of lost solute in the valve or restrictor.Our group developed a new high-temperature and-pressure optically transparent reactor FSCR, combined with heating/cooling stage,real-time digital video analysis system and Raman spectra. So far, thedevice successfully determined the solubility of chlorobenzene,4-chlorotoluene, 2,4-dichlorotoluene, o-chlorotoluene, and2,4-dichlorofluoro-benzene in subcritical water.We used the tubular heater and FSCR to explore the stability of m-chlorotoluene, 1,2-dichlorobenzene in subcritical water,and measured the solubility. Combined with real-time digital video analysis system observing the phase change in the process of dissolution. In addition, the Raman spectra of m-chlorotoluene, 1,2-dichlorobenzene, solvent(water)and pure water were collected during its process of dissolution with the rise of temperature. Specific contents are as follows:(1) After the process of 15 h and 20 h “heating- thermostat –temperature” respectively to 240 ℃ and 286.3 ℃ in the solution of m-chlorotoluene and 1,2-dichlorobenzene, the solute dissolved completely,and the solute-water system reached a homogeneous mixing state.(2) Staying at 320 ℃ for 9 hours, the average recoveries of three samples of m-chlorotoluene and 1,2-dichlorobenzene were 98.4% and98.3% respectively. It can be considered that there was almost no oxidation and hydrolysis for m-chlorotoluene and 1,2-dichlorobenzene in water regardless of personal error and system error of equipments.(3) The solubilities of m-chlorotoluene and 1,2-dichlorobenzene in the range of 249.2~294.9℃ and 256.7~294.1℃ respectly were obtained using the FSCR combined with a microscope recorder system, The results showed that the solubilities of m-chlorotoluene and 1,2-dichlorobenzene increased linearly with increasing temperature.