Study On Phase Equilibrium At High Pressures For The Systems Of Synthesizing Diphenyl Carbonate

Diphenyl carbonate is an important aromatic carbonate. Its related reactants such as carbonate monoxide, oxygen, phenol, dimethyl carbonate, methanol and ethanol and so on, were chosen as the systems that were studied on phase equilibrium at high pressure.The solubilities of CO and O2 in some above solvents and their mixed solvents were determined at the pressure range from 2.0 MPa to 9.0 MPa by a set of the experimental apparatus through cycle method for gas liquid equilibria systematically. The experimental results show that all the solubilities of CO and O2 in unitary solvents and their mixed solvents are increased along with the rise of pressure.The calculation of gas liquid equilibrium for the ternary systems can be figured up using various cubic equation of state, ie SRK, PR and PRSV EOS etc. At the same time, the diversity mixing rules, for example, the traditional quadratic form mixing rules, Wong-Sandler mixing rules, MHV1mixing rules, NRTL mixing rules and van Laar mixing rules, were coupled with the expression of the constant of EOS. Henry's constants of CO and O2 in the single solvent and mixing solvents were fitted to the experimental data .The binary interaction parameters kij and the binary interaction energy parametersΔgij were regressed from the solubilities for the experimental systems for CO-C6H5OH-C2H5OH,CO-(CH3O)2CO-CH3OH,O2-C6H5OH-C2H5OH and O2-(CH3O)2CO-CH3OH, respectively. It is fairly obvious from the correlated results that the agreement between experimental data of solubility and calculated ones with the proposed model (method 8) was rather satisfactory. The mean error is less than 2 %. The fugacity f? iL for the components CO and O2 has a good linear function. At the constant temperature and pressure, the new model can be presented on the relationship between the fugacity f? iL and the mole fraction of component (1) x1 in the mixed solvents.Furthermore, the activity coefficientsγi for the component i in the binary systems such as phenol-ethanol, oxygen-dimethyl carbonate can be computed by employing UNIFAC method. A new group carbonate-group has been defined in dimethyl carbonate and its group volume parameter, group surface area parameter and group interaction energy parameters in the studied systems were derived from the experimental data. It should be noted that these parameters is a supplement because carbonate-group is lack in the UNIFAC method literatures. According to the calculated results, they have an approving agreement with the experimental solubilities. The mean error calculated is 0.675%。Besides, the prediction of solubility can be suitable for O2 in C6H5OH-C2H5OH and (CH3O)2CO-CH3OH mixed solvents, respectively. But the calculated accuracy for the gas liquid equilibrium at high pressure is inferior to one obtained from EOS method.On the other hand, the densities were measured by a vibrating densimeter and the excess molar volumes VE were calculated at five temperatures and atmospheric pressure for phenol-ethanol. By the improved Redlich-Kister equation, the model parameters of VE were fitted to the experimental density data at the temperature range from 298.15 K to 348.15 K.For prediction of the thermodynamic property for phenol-ethanol, the AE was discussed by SRK EOS coupled with HVOS mixing rules. It can be concluded that EOS method can be used for the calculated of the liquid solution by matching the mixing rules. Hence these works are an investigated basis of the activity coefficient.In a word, firstly the measured solubilities of CO and O2 in unity solvent and mixed solvents and its computed model may be an essential data provided for the synthesis technology and separation process of diphenyl carbonate. Secondly, the definition and the regressive parameters of new carbonate-group will make the calculation of group contribution more realiable. Finally, the excess molar volume and the excess Helmholtz free energy were studied, and a series of activity coefficient were first presented so that it makes the prediction of the thermodynamic property for phenol-ethanol becomes possible.