Refining The Benzene And Recovering The Thiophene By Extractive Distillation

With the development of the coking industry, coking benzene is becoming an important source of benzene, but it always contains alkanes and alkenes, which could form azeotropic mixture with benzene. The traditional separation method could not fit the development of the environmentally friendly chemistry. This paper refines the benzene and recovers the thiophene through extractive distillation technology.The key of the extractive distillation is the choice of solvent. In the paper it evaluates solvents that had been reported with UNIFAC model: N-methylprolinodone (NMP), Dimethyl sulfoxide (DMSO), Dimethyl formamide, Morpholine, Aniline, Diphenyl methane, Ethanediol, Diglycol, Tetraethylene glycol (TEG), Sulfolane. And hexane, cyclohexane, methyl cyclohexane and 1-heptane are selected as the representative of alkanes and alkenes. It is proved that Sulfolane, DMSO, TEG, NMP and Dimethyl formamide are effective solvents. However, considering for the BP and toxicity, NMP is selected as solvent in the extractive distillation experiment.The experiment is composed of three parts: the process of removing alkanes and alkenes, the process of refining benzene and the process of purifying thiophene. In the first stage, alkanes and alkenes are removed mostly by once extractive distillation, and the thiophene is maximumly preserved, so it lays the foudation for the follwing stage. The high quality benzene is obtained in the second stage, and the thiophene could not be detected through GC. In the end, high concentration thiophene up to 99% (in mass) was recovered successfully. Different reflux and solvent ratio are adopted in the experiment process, and the effect of the operation parameters is discussed.At last, the extractive distillation process is simulated, and the optimal operation parameter is obtained. Different component split in different product steams is analyzed during three different stages, and the greatest yield is calculated in an ideal operating condition without any waste. At the same time, the temperature profile and concentration profile are analyzed along the extractive distillation column and solvent recyling column.