| 1,6-Diaminohexane?DAH?and trans-1,2-diaminocyclohexane?trans-1,2-DACH?are important chemical raw materials and intermediates,which are widely used in many fields.In this paper,the vapor-liquid phase equilibrium,volume and viscosity properties,intermolecular interaction,liquid-liquid phase equilibrium and extraction kinetic which related to the mixed C6 diamines?water,DAH and trans/cis-1,2-DACH?were studied in detail.Based on these investgations,the separation process of the industrial mixed C6 diamines was proposed.The binary vapor-liquid phase equilibrium of?water+trans-1,2-DACH?,?water+DAH?and?trans-1,2-DACH+DAH?were investigated.The thermodynamic consistency of the experimental data was checked.The Wilson,NRTL and UNIQUAC models were used to correlate the experimental data and the model parameters were obtained.The average relative deviations between Wilson model calculated results and experimental values for the three binary systems were 0.66%,0.51%and 0.48%,respectively.It was demonstrated that Wilson model can give better calculation results for the three binary systems.The industrial C6 diamines mixture can be separated preliminarily by the distillation method since the calculated value of the relative volatility between any two components are more than 1.32 and there is no azeotropic phenomenon exsting in the mixed systems.The density and viscosity of the separated components are the basic data in the design process of distillation.The density and viscosity of?trans-1,2-DACH+water?and?DAH+water?binary systems were measured in this paper,from which,the excess molar volume?VE?,excess viscosity????and excess Gibbs flow activation energy(?G*E)were calculated.All of the experimental density,viscosity and excess properties data were fitted,and the related model parameters were acquired,respectively.The results show that,the value of VE for the two binary mixtures are all less than zero,both the value of??and?G*E are larger than zero,the effect of temperature on the position(x1m)of VEmin,?max and??max are negligible.Besides,the viscosity of the binary systems increased to?max firstly and then decreased slowly to the state of pure C6 diamines?trans-1,2-DACH or DAH?with the increase of C6diamines.The higher?max data of?trans-1,2-DACH+water?than?DAH+water?demonstrates that the strength of the intermolecular interaction between water and diamine in this system is larger than?DAH+water?system.The intermolecular interaction structure and energy characteristics between water and C6 diamines?trans-1,2-DACH or DAH?were studied at M06-2X/6-311G?d,p?level.By analyzing the electrostatic potential of the monomer molecular,the configurations of the dimers?trans-1,2-DACH…H2O or DAH…H2O?and trimers?trans-1,2-DACH…H2O…H2O or DAH…H2O…H2O?were built and optimized and the stable configurations were obtained,the BSSE and ZPE corrected binding energies were acquired.The theory of atoms in the molercular was used to determine the electron density at the bond critical points both in the dimers and trimers.The results show that the binding energy between water and trans-1,2-DACH is larger than water and DAH,indicating that the strength of the molecular interaction between water and trans-1,2-DACH is stronger than water and DAH.The binding energy and the electron density at the bond critical points of the trimers are higher than the dimers while the hydrogen bond distance of N…H-O and O…H-O are shortened,demonstrating that the H–bond in the trimers were enhanced,which means that the synergy effect exsiting in the trimers.The sites and intensities of the hydrogen bond,van der Waals interaction and steric hindrance between H2O and C6 diamines were studied visually by the non-covalent interaction?NCI?method.On this basis,the viscosity behavior of the?C6 diamine+water?binary system and the reason for the higher?max and??max of?trans-1,2-DACH+water?system were explained.Extraction is one of the important stages in the trans-1,2-DACH resolution process,and the key step is the selection of appropriate extraction agent.In this paper,two kinds of solvent models SMD and COSMO-RS were used to predict the solvation free energy of 19 kinds of organic amine in water and 4 kinds of which in organic solvents.SMD model prediction value was found to be nearer to the experimental data.The solvation free energies of trans-1,2-DACH in water and 11 kinds of organic solvents were calculated by using SMD model and the distribution coefficients between different organic solvents and water were predicted based on the obtained solvation free energies.The solvents of 2-methyl-1-propanol and 3-methyl-1-butanol were screened out to act as the extraction separator.On this basis,the liquid-liquid phase equilibrium and solubility data of the ternary systems?2-methyl-1-propanol or3-methyl-1-butanol+trans-1,2-DACH+water?were studied and the obtained phase diagram can provide a theoretical basis for determination of the theoretical series of cross-flow extraction and the amount of extraction agent.The reliability of the experimental data was verified.NRTL and UNIQUAC models were used for regression of the experimental data and the interaction parameters between the components were obtained.The distribution coefficient?D?and separation factor???were obtained according to the liquid-liquid equilibrium data.It was found that both D and?were greater than 2 indicating that both of the two extractants could be used for the extraction of trans-1,2-DACH in the aqueous phase.In this paper,2-methyl-1-propanol was used as the extraction agent and cyclohexane as the diluent,the kinetic characteristics of trans-1,2-DACH extraction process were studied using the constant interfacial cell method.Within the range of the experimental study,the initial extraction rate of trans-1,2-DACH increased with the increasing of the two-phase stirring speed,two-phase interface area,temperature,the initial concentration of trans-1,2-DACH in the aqueous phase,and the concentration of the extractant in the organic phase.The apparent activation energy was 18.16 kJ·mol-1 indicating that the extraction process belongs to a diffusion control type.The extraction rate equation was built and the total mass transfer coefficients which based on the aqueous phase and the extracted organic phase(KLaqaq and KLo)and the apparent equilibrium distribution coefficients?KP?were obtained according to the kinetic data.The results indicate that the extraction process is far from the thermodynamic equilibrium?KP<D?and the mass transfer resistance mainly exist in the water phase(KLaq<KLo).The statistical test and residual analysis results indicate that the established extraction rate equation can give better description of the extraction mass transfer characteristics of the studied system.The distillation and chemical resolution combined separation process of the industrial mixed C6 diamines was proposed.Based on the vapor-liquid phase equilibrium data,the number of the theoretical plates needed to separate 1,2-DACH and DAH under different conditions was calculated by stage-by-stage calculation method.After the twice vacuum distillation,the mass purity of 1,2-DACH and DAH were 99.1%and the recovery were 80.3%and 90.0%,respectively.The chemical separation of 1,2-DACH was carried out with the resolution method,the optical purity of?-?-trans-1,2-DACH and?+?-trans-1,2-DACH derivatives analysed by high performance liquid chromatography was up to 99.5%,the purity of cis-1,2-DACH analysed by gas chromatography was about 96.7%. |
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