Experimental Study On Salting-out Regeneration Of Dearomatized And NMP Rich Liquids Extracted From Low Aromatic Naphtha

The concentration of the aromatic hydrocarbons in naphtha,will directly affect the subsequent processing,product quality and the using range.Meanwhile,many countries are imposing increasingly severe limits on the aromatic hydrocarbons in food,medicine and daily necessities,especially strict limits of benzene,solvent oil should also need further dearomatization.Aromatics extraction is the main means to separate aromatics from reformate and FCC gasoline in the industry and the extraction solvent regeneration method is stripping or vacuum distillation that has problems of large investment and high energy consumption.Therefore,the study of the extractants for low aromatic naphtha and solvent regeneration technology of energy saving and environmental protection has a certain practical significance and application prospect.By considering the selective coefficient,distribution coefficient,the physical and chemical properties of solvent,we have selected the DMF-PC composite extractants,which has a high aromatic selectivity and low non-aromatics solubility in this paper.Aiming at the extraction effect of DMF-PC for low aromatic naphtha,we have done systemic research on theory and practical application in this work.Liquid-liquid equilibrium data for the system{n-Heptane + Benzene + DMF},{n-Heptane + Benzene + DMF} and {n-Heptane + Benzene+ DMF + PC} were determined experimentally at different temperatures and atmospheric pressure.The consistency and reliability of the experimental LLE data was ascertained by applying the Othmer-Tobias and Hand correlation.The experimental LLE data was correlated with NRTL and UNIQUAC activity coefficient model.DMF-PC was applied in aromatics extraction of low aromatics naphtha.When extraction temperature was 45 ?,extraction time was 5min,phase separation time was 10min,single stage extractant oil mass ratio was 0.5 and ten-stage counter-current extraction,volume ratio of washing water to oil was 9%,the mass fraction of aromatics in naphtha reduced from 15%to 4.48%,dearomatization rate was 70.16%,naphtha yield was 73.89%and solvent content was 0.0341%.At the same time,from the point of salt effect,we have aslo studied the solvent regeneration of the N-methyl pyrrolidone as the solvent for aromatics extraction system.When regeneration temperature was 25 ?,the salting-out agent was SOA solution(mass fraction 5%)and its dosage was 1.3ml/(20 ml NMP rich fluid),the salting out yield was 81.81%.By comparing the extraction effect of regenerated and fresh NMP,showed that NMP rich fluid regenerated by the way of salting out and vacuum distillation is feasible.