Study On Related Fundamental Research Of New Separation Process Of C5 Fraction And Selection And Optimization Of Extractive Agent

Linear solvation energy relation was firstly introduced in the paper, and the method and step of gaining the special parameters of solvent and solute were introduced in detail, and these special parameters were used to selection and optimization of extractive agent in extractive distillation. The model of predicting activity coefficient at infinite dilution was established by linear solvation energy relation. By the above theory, several candidate solvents were selected to separate C5 fraction, and by experiment of vapor-liquid phase equilibrium at atmosphere pressure, the mixture of N-methyl-pyrrolidone including 4% water was used extractive agent of separating C5 fraction. Then binary vapor-liquid phase equilibrium of the some compound in C5 fraction and N-methyl-pyrolidone were determined at atmosphere pressure and correlated by NRTL equation. Isoprene being objective compound, experiments were operated in the laboratory-scale column; the processes were simulated by RadFrac model in ASPEN PLUS. And by the combination of experiment and simulation, the new process of separation of C5 was established. In the paper, the main works were as follows:1. Linear solvation energy relation was firstly introduced, the special parameters of solvent and solute which wereπ~*,αandβwere also introduced, the scale ofπ~* described the ability of solvent-solute action by dipolarity and polarization; Theαscale of solvent/solute HBD (hydrogen-bond donor) acidity described the ability of solvent/solute to donate a proton in a solvent-to-solute hydrogen bond; theβscale of solvent/solute HBA (hydrogen-bond acceptor) basicity described the ability of solvent/solute to accept a proton in a solvent-to-solute hydrogen bond. By these special parameters extractive agent was selected and optimized qualitatively. 2. The model of predicting activity coefficient at infinite dilution wasestablished by linear solvation energy relation, and the unknown parameters in the model were gained by linear correlation of abundant experimental values of activity coefficients at infinite dilution.3. The mixture of n-pentane and isoprene was model mixture in C5 fraction, by above selection and optimization of extractive agent theory, 7 kinds of solvents were used as candidate solvents.4. The vapor-liquid equilibrium equipment was set and was checked by literature values, the results showed the equipment could be used to determine vapor-liquid equilibrium at atmosphere pressure. The mixture of n-pentane and isoprene was used model mixture of C5 fraction, and effect on separation of the mixture of 7 solvents were studied by experiment, by combination of separation effect and other characteristics such as toxicity, stability, and so on, N-methyl-pyrrolidone was selected as extractive agent of the separation process of C5 fraction. The optimization of N-methyl-pyrrolidone was studied by vapor-liquid equilibrium experiment, and the result showed the mixture of N-methyl-pyrrolidone including 4% water could be better extractive agent than others.5. Vapor-liquid equilibrium of the important compound and N- methyl-pyrrolidone at atmosphere pressure was performed, and all values passed the thermodynamics consistency test by Herington method. These values also correlated by NRTL and RK equations; the binary interaction parameters and nonrandom factors in the NRTL equation were gained. These datum were the base of simulation.6. Isoprene being objective output, the experiments were performed in the laboratory-scale column. The process was two steps: the first step was extractive distillation, in the step some operation conditions were studied and gain a lot of experimental values; in the second step, ordinary distillation and extractive distillation were performed, respectively, some operation conditions were performed and a lot of data were gained. By comparing the separation effect of two method in the second step, the ordinary distillation was used because separation effect and simplicity.7. The experimental conditions were simulated by RadFrac in ASPEN PLUS, and the thermodynamics models were NRTL and RK equation in liquid phase and vapor phase, respectively, in extractive distillation process while the model was PR equation in the ordinary distillation, the calculated values agreed with the experimental values. RadFrac was used to simulate and optimize the separation processes of C5 fraction by above thermodynamics models.8. By simulation, the optimal operation conditions were gained in every step in the separation process, and polymerization-class isoprene was gained by the process. And to improve the economy of process, the process was studied by simulation, 99% cyclopentene and 1, 3-pentadiene were gained by continuous separation process. All were the base of the process industrialization.