Study On The Phase Equilibrium Of The System Of P-aminophenol Synthesized By Nitrobenzene Hydrogenation

P-aminophenol is an important organic intermediates which is widely used. Theresearch of phase equilibrium in crystallization process of p-aminophenol in zinc sulphatesolution was carried out and the batch distillation process of aniline was simulated andoptimized based on the requirements of new synthesis crafts of p-aminophenol throughhydrogenation of nitrobenzene, whose results had an important guiding significance on theindustrial scale design of the separation process.The solubility of p-aminophenol in various concentrations of zinc sulfate solution wasdetermined by balance method under atmospheric pressure with the ranging of temperaturefrom286.15-353.15K. Results showed that the effect of the concentration of zinc sulfatesolution on the solubility of p-aminophenol had relationship with temperature. There wasless disparity of solubility of p-aminophenol between various concentrations of zinc sulfatesolution and the higher the temperature, the greater the difference. Zn2+in solution ligandedwith p-aminophenol to form soluble ammonia complex of zinc through UV analysis, thehydrolysis of zinc ions exacerbated and also the content of the complex correspondinglyincreased as the temperature raising and that lead to the increase of solubility ofp-aminophenol.Solubility of p-aminophenol in water was correlated by a modified NRTL model andthe binary interaction parameters of water and p-aminophenol were calculated. Thethermodynamic model was used to associate the solubility of p-aminophenol in water withthe temperature ranging from286.15to353.15K and the average relative deviation was0.71%. The long-range electrostatic interaction between ions and the short-rangeinteractions of moleculars were both existed when p-aminophenol dissolved in zinc sulfatesolution. Fowler-Guggenheim equation was adopted to caculate the long-range interactionterm and the short-range interaction term was associated with the modified NRTL activitycoefficient model, Fowler-Guggenheim-NRTL activity coefficient model of p-aminophenolin zinc sulfate solution was established and the binary interaction parameters ofp-aminophenol and ZnSO4were regressed. The solubility data of p-aminophenol indifferent concentrations of zinc sulfate solution was calculated by the thermodynamic model and there was a good agreement between the calculated and experimental valueswith relative average deviation of4.58%and the accuracy met the requirements.The batch distillation process of aniline-p-aminophenol-water system was simulatedby Aspen Plus as the UNIFAC thermodynamic model was selected. The estimatedthermodynamic properties of each component by UNIFAC model of aniline-p-aminophenol-water ternary system agreed well with literature values indicating that the UNIFAC modelfitted the system. The jacket temperature and operating pressure of the distillation processhad been optimized and simulated, the amount of one-pot capacity was500Kg and thedistillation time was2.33h under the conditions that the suitable jacket temperature was160℃and the distillation pressure was0.081MPa, the aniline concentration in kettle andthe remaining water met the design requirements.