Separation Of Non-polar System Of Benzene And Cyclohexane By Extraction With DMF And KSCN

For both the formation of azeotropic and the low relative volatility (volume fraction of components from 0 to 100%) of the mixture, the efficient separation of benzene and cyclohexane has become academic research topic. The existing methods are azeotropic distillation, extractive distillation and pervaporation, which still have their own limits.Because benzene can be mutually soluble with organic solvents and layered difficultly, it is more difficult to separate benzene - cyclohexane system by extraction technology, and up to now, there are still no related reports about it. When DMF was mixed with benzene-cyclohexane system, the mixture was uniform without stratified, and couldn't be extracted. However, when KSCN was added into DMF to form the new solvent, and then mixed with benzene-cyclohexane system, the system was quickly stratified, and could be extracted.Separating benzene-cyclohexane azeotrope with single stage extraction by DMF+KSCN has been studied, when the changing of partition coefficient and selectivity coefficient under different ratio of solvent and concentration of KSCN has been researched. At same time, experiments of multistage cross (counter) current extraction and distillation have also been done, and technological process has been designed. The experimental results indicated that: when the concentration of KSCN was between 15% and 18%, the ratio of solvent was 1:1, the require of separation could already be satisfied, and the complex solvent were much better to separate the material with benzene less than 50%( volume concentration); after seven stages cross current extraction, cyclohexane's molarity can be 97.79% ( without solvent); after five stages counter current extraction, cyclohexane's molarity is more than 71%(without solvent); when single stage extraction were coupled with distillation, 97.2% of benzene can obtained in the tower top, and the DMF+KSCN in tower kettle were more than 95%; when counter current extraction was coupled with distillation, cyclohexane's molarity is more than 98% and benzene's molarity is more than 97%. According to the above results, the theory of salt effect were used to preliminary study the mechanism of separating the non-polar system of benzene and cyclohexane by extraction with the solvent of DMF+KSCN. DMF+KSCN complex solvent is an excellent mass separation agent for extracting benzene and cyclohexane. It is absolutely according with the selection principle of the extraction solvent. Extensing the separation of benzene and cyclohexane by extraction with DMF and KSCN complex solvent has a high industry value.