Study On Extraction Process Of Biphenyl By Supercritical Ethanol From Washing Oil

Coal tar is an important product of coking industry, and it contains very rich compoundswhich are valuable chemical raw materials. Washing oil is the fraction that is cut at atemperature range from230~300℃(GB-3064), and it is mainly used to wash and absorbthe benzene hydrocarbon of coke oven gas currently. Besides, lots of high value-addedcompounds included in the washing oil are not widely used.The process of coal tar industry has high energy consumption and serious environmentpollution. Besides, its scale is still a little small. As the domestic production of coal targradually increase, people pay more and more attention to protecting environmental. Theresearch and development of green chemical separation technology is imminent. Supercriticalfluid has excellent solubility. The application of supercritical fluid extraction technology incoal tar under mild conditions could not only save energy but also protect environment.Moreover, the solvents of extraction are easy to be separated and could be recycled.In this experiment, Biphenyl and Indole were extracted by supercritical ethanol.According to the efficiency of the supercritical ethanol extraction, the main factors includingpressure and temperature were studied. The products were analysed through gaschromatography. We have carried on the preliminary discussion about the mechanisminfluenced by each factor. Lastly, according to the law and the best conditions before, theverified experiment about the wash oil of WISCO which had been processed was carried out.The results turn out that Biphenyl and Indole have the similar solubility in thesupercritical ethanol. The maximum extraction rate of Biphenyl reaches46.15%under theconditions of the temperature at275℃, volume ratio at0.70and pressure at12.2MPa. Atthe same time, the extraction rate of Indole also arrives the maximum50.49%. The bestconditions of supercritical ethanol extraction about Biphenyl and Indole is effective, when itis used to extract the Biphenyl in the actual wash oil. Biphenyl has a1.50%extraction rategap between the light wash oil and the single component. But Indole has a17.71%extractionrate gap.