Study On The Solubility Characteristic Of Supercritical CO₂ With Cosolvent System

The solubility of solute in SCF is the key point of the design for the apparatus and the scale-up for the processes such as supercritical fluid extraction and super micro-partical manufacture and preparation of organic/inorganic composite nanomaterials.The phase behavior of the solid solute in SCF is more complex.So it is more important to study the solubility of solid in SCF both in experiment and calculation.Firstly,We studied the solubility of inorganic cupric nitrate in supercritical CO₂ with eosolvent ethanol over the pressure range 7.8～23.SMPa,from the temperature 313.15～333.15K.And we also analyzed the effects of equilibrium time,dosage of cosolvent,pressure and temperature on the solubility of cupric nitrate.Besides,we also studied the solubility of inorganic silver nitrate in supercritical CO₂ with cosolvent ethanol and glycol over the pressure range 10-25MPa,from the temperature 323.15～333.15K.And also we analyzed the effects of pressure and temperature on the solibility of silver nitrate.From the experimental results we find that both the cupric nitrate and silvier nitrate solubilities increase with the increasing of pressure.There is a crossover pressure in the solubility curve.When the pressure under the conversion point,the solute solubilities increase with the decreasing of temperature.When the pressure over the conversion point,the solute solubilities increase with the increasing of temperature.So far,the experience solubility calculation models are mainly based on density.We found a model which is suit for calculation the solid solute solubility in SCF with/without cosolvent bases on solubility parameter(named SPM).We have calculated seventeen binary systems and thirteen ternary systems by the SPM,which have pubulished on the intemet.From the result we can make sure the SPM model is suit for the calculation of solid solubility under supercritical state.As a whole,the average absolute relative deviation is under 8.5%(binary systems) and 6.0%(ternary systems).Which is more accuracy than the result of christal model(AARD=14.98).Finally,we chosed COMPASS force field and periodic boundary conditions.The equilibration course adopted NPT ensemble,and the analytical course adopted NVE ensemble. Constant pressure and temperature adopted Andersen arithmetic.The initial velocity adopted the Boltzmann random distribution.Base on the solubility of naphthalene in supercritical CO₂ made sure the molecular number of naphthalene and carbon dioxide.We have studied the infinite dilute diffusion coefficients of naphthalene in supereritical CO₂ and in supercritical CO₂ with cosolvent methanol,respectively.Calculation results showed good agreement with literature datas.The infinite dilute diffusion coefficients of solute decreased with the increasing of system pressure.Besides,nearby critical point diffusion coefficients increased dramatically with the decreasing of pressure.Under the same pressure,the diffusion coefficients of solute increased with the increasing of temperature.