Liquid-liquid Equilibrium For Extraction Separation Of Toluene And Methylcyclohexane Using N,N-dimethylformamide And Potassium Thiocyanate

Toluene and methylcyclohexane are both very important chemical products,their range of application are second compared to benzene and cyclohexane.There are a lot of aromatic hydrocarbon and non-aromatic hydrocarbon in the Coal liquefaction oil distillate fractions,the content of toluene and methylcyclohexane are too much,in the industry,what we need mostly are pure toluene and methyl cyclohexane,therefore the separation of toluene and methylcyclohexane is very important.The equipment investment and energy consumption are very large when using traditional distillation operation to separation of toluene and methylcyclohexane.As a result,the industry need to find an effective way to separation the mixture of toluene and methylcyclohexane.Liquid-liquid extraction is one of the most widely used industrial separation technology.It can be used to separate the system which the traditional distillation can't separate or separation costs is high.In this paper,we chose the liquid-liquid extraction to separate toluene and methyl cyclohexane system,ammonium thiocyanate and N,N-dimethylformamide is used as the extraction solvent to separate toluene and methylcyclohexane,the liquid-liquid equilibrium datas of the quaternary system toluene+ methylcyclohexane+ ammonium thiocyanate+ N,N-dimethylformamide are measured at different temperatures and different salts concentration.the selectivity coefficient of the solvent and the distribution coefficient of the solute in this quaternary system are calculated,ans triangle phase diagram of quaternary system is drawn by at 25? and 30?.we can reach the conclusions by analyzing the equilibrium data:the mass fraction of ammonium thiocyanate in the co-solvent is related to selectivity coefficient of the solvent,And as a general rule,As the mass fraction of ammonium thiocyanate in composite solvent get larger,the selectivity coefficient of solvent becomes larger.when the temperature is 25?,in the quaternary system which is measured and calculated,the range of selectivity coefficient is 2.2781~10.7431,the range of distribution coefficient is 0.0871~0.7243;when the temperature is 30?,the range of selectivity coefficient is 1.6535~14.0247,the range of distribution coefficient is 0.0997~0.6362.The experimental data of the quaternary system are correlated by Othmer-Tobias equation and Hand equation.It can be seen from analysis the degree of fitting and standard deviation,the quaternary system can be well associated with these two equations;on this basis,the experimental data of the quaternary system is correlated by the NRTL equation,when the temperature is 25?,the standard deviation is 0.0054 and when the temperature is 30 ?,the standard deviation is 0.0077.The root-mean-square Deviation between the measured data and the predicted data are calculated.The results showed that without the quaternary system which the salt content of lesser is dissatisfied,the other salt content of the quaternary system are very good.