Liquid-liquid Extraction Separation 1,1,2-trichloroethane - Research Dimethylformamide Mixtures

The applications, production technology, future prospect of trichlorosucrose were summarized in this paper. The problem of solvent recovery during the manufacture of trichlorosucrose, that is, separating the mixture system of1,1,2-trchloroethane and N,N-Dimethylformamide, was analyzed. The performance and applications of N,N-Dimethylformamide and1,1,2-trchloroethane were introduced. What’s more, the difficulty in separating and purifying the mixture system of1,1,2-trchloroethane and N,N-Dimethylformamide were analyzed and the recent methods of separating N,N-Dimethylformamide from its solution were reviewed in the paper. Then, an advanced method of liquid-liquid extraction was carried out to separate N,N-Dimethylformamide from its solution.According to the general principle of extractants selections and different solubility characteristics about1,1,2-trchloroethane and N,N-Dimethylformamide, some new researches and experiments were carried out, it turned out that water could be chosen as the right extractant to separate1,1,2-trchloroethane-DMF mixed solution.Further, the extraction capacity of water was discussed from the view of equilibrium. Different influencing factors on the liquid-liquid equilibrium such as stirring time, stirring velocity and setting time were studied in detail on the basic of which the liquid-liquid data were tested. The interactive parameters of NRTL and UNIQUAC equation were correlated, the basic LLE data were simulated. The results showed that both NRTL and UNIQUAC equation were suitable.On the basic of simulation results, experiments of cross-flow extraction were conducted, considering the influencing factors of solvent ratio and extraction progression. The results showed that the purity of1,1,2-trchloroethane could be more than99.50%by four extraction progressions at the ratio S:F=1:1. Meanwhile, the recovery of DMF could be more than99.50%.Experiments of continuous countercurrent extraction were conducted, considering the influencing factors of raw ratio. The results showed that in the condition of8theoretical series of continuous countercurrent extraction column, the purity of1,1,2-trchloroethane was99.30%at the ratio S:F-1:1. The results of continuous countercurrent extraction agree with the results of cross-flow extraction. Finally, the purity of1,1,2-trchloroethane could be99.50%after cross-flow extraction, therefore, higher purity product can be get by distillation. Meanwhile, a few amount of DMF could be recycled through multi-distillation according to literatures.A whole liquid-liquid process of separating1,1,2-trchloroethane-DMF system has been provided in this paper. Both cross-flow extraction and continuous countercurrent extraction were carried out to separate the mixture, whose process is simple, energy consumption is low and yield is high. The study would provide fundamental references for further industrialization process of separation of1,1,2-trchloroethane and DMF.