Basic Research Of The Technology For Extracting Aromatics From Heavy Naphtha

As the ethylene cracking raw material, the quality of naphtha has a very importantinfluence on the olefin yield. Removal of the aromatics from naphtha could not only improvethe olefin yields of naphtha cracking, but also effectively reduce the coking of crackingfumace and prolong its operation cycle. Therefore, the study of removing aromatics fromnaphtha especially heavy naphtha will be of important significance.In this paper, liquid-liquid extraction has been adopted to remove aromatics from heavynaphtha. More than ten kinds of extractants, like furfural, sulfolane, DMSO, NFM, etc, areselected for the liquid-liquid extraction experiment.The liquid-liquid equilibrium data of theheavy naphtha extraction systems and the relative correction factors of the main solvents aremeasured,so as to get the best single solvent for this heavy naphtha extraction system.Underthe condition of different technological parameters, the extraction performances of(furfural+sulfolane),(furfural+DMSO),(furfural+water),(sulfolane+furfural) and (DMSO+furfural) are studied. And at last the best extractant for extracting aromatics from heavynaphtha is screened.The results show that, the values of relative correction factors for furfural, sulfolane,DMSO and NFM are2.34,2.55,2.69and3.05respectively, and the hydrocarbon componentsin heavy naphtha are identified as1.0. Furfural is the best single solvent for this heavynaphtha extraction system. On the condition of50℃(extraction temperature),4:1(solvent/oil),mixing time1.5h and setting time3.0h, the paraffin content of the raffinate oil for the furfuraland heavy naphtha extraction system is up to68.66%, increasrd by9.93%compared with theraw naphtha. In the (furfural+0.50%water) and aromatics extraction system, on the conditionof50℃(extraction temperature) and4:1(solvent/oil), the paraffin content of the raffinate oil is up to69.40%. However the added of water cannot increase the extraction rate of the heavyaromatics. Sulfolane and (sulfolane+furfural) have almost no extraction ability to aromaticsthat contain more than ten carbon atoms.In the (DMSO+furfural) and aromatics extraction system, the paraffin content of theraffinate oil is positively correlated with the extraction temperature, ratio of reagent to oil andextraction stages. Under the condition of50℃,3:1(solvent/oil),(DMSO+20.00%furfural) canmake the paraffin content of the raffinate oil reach to71.35%after five stages extraction,which improved by12.62%compared with the raw naphtha. It can be seen that,(DMSO+20.00%furfural) complex solvent is a good solvent for the heavy aromaticsextraction.