Study On The Separation Of Toluene/n-Heptane By Supported Liquid Membranes With Ionic Liquids

In the background of the extending need and the shortage of petroleum,although separation of aromatic and aliphatic hydrocarbons after the furnacesection is industrial practice, the cracker feed has not yet been considered.Removing the major part of the aromatic compounds present in the feed to thecrackers would offer several important advantages：higher capacity, higherthermal efficiency and less fouling. As the main raw material of ethylenecracker, making full use of the naphtha has become an important researchsubject.As a green solvent，Ionic liquids （ILs） with the unique physical andchemical properties, is considered as alternative agent for conventionalsolvents. Ionic liquids have a good separation performance when extractingseparation aromatics/alkane, but ILs is expensive for now, will need high cost.Supported liquid membrane have an edge of simultaneous extraction andstripping processes in the same stage, low solvent inventory, Combining withthe high viscosity and nonvolatility of ionic liquids, Supported liquid membrane with ionic liquid was set up, which can improve the stability ofliquid membrane process and reduce the consumption of ionic liquid. the costof separation of aromatic and alkane mixture will be reduced.In this paper, the separation of toluene/n-heptane were investigated byusing [4-MeBuPy][BF4]、[Bmim][BF₄] and [Emim][BF₄] as extractants viasolvent extraction and SILM（supported ionic liquid membrane）. The effect ofvarions parameters including the initial concentration of toluene in raffinate，ionic liquid species in the SILM used，the temperature of the receving solutionand the initial concentration of toluene in feed. It was found that all of ioncliquids was used in this study can provide excellent separation selectivity fortoluene/n-heptane extraction. The separation process of toluene/n-heptaneusing SILM was proved to be feasible. The temperature of the recevingsolution and the initial concentration of toluene in feed solution bothsignificantly affected the separation process.The interaction mechanism of ILs and toluene、n-heptane were studiedthrough quantum chemistry. The structure parameter and electronic structruewere calculated at B3LYP/6-31G*level． The results indicated that theinteractions of ILs and toluene much higher than ILs and n-heptane. Theinteractions enhanced stabilisation of the solute in ionic liquids, whichexplains the observation that aliphatic compounds in general were less solublethan aromatic compounds. The study developed the mass transfer model forthe separation process by introducing the notion of group contribution method. The results of theoretical calculation and experimental data contrastedconsiderably. Model on the experiment has certain forecasts and guidance.