| Nowadays,with the rapid development of global industrial processes and the shortage of petroleum resources,the effective separation of aromatic alkane mixtures is the key to making full use of petroleum resources.The eutectic solvent(DESs)is a liquid formed by a hydrogen bond donor(HBD)and a hydrogen bond acceptor(HBA)according to a certain stoichiometric ratio.Compared with other extractants,it is safe,environmentally friendly and simple.The new extractant has a wide range of applications in the chemical extraction and separation process.Therefore,DESs have great application prospects in the separation process of hydrocarbon compounds.In this paper,two systems,benzene-cyclohexane and toluene-n-heptane,were studied.According to the the theory that aromatic hydrocarbon having a benzene ring structure,it can be separated from the aromatic heterocyclic structure to form a ?-? bond,which were designed and synthesized.The DESs were characterized by NMR and Fourier transform infrared spectroscopy.HBD played a primary role,while the HBA played a secondary one in the process of aromatics separation.N-formylmorpholine(NFM),levulinic acid(La),ethylene glycol(EG)were selected as HBDs,and 1-ethylbromide pyridine(C2py)was used as HBA was investigated to get good extraction efficiency.The three DESs(C2py-NFM,C2py-La and C2py-EG)were prepared,and two ternary systems,benzene+cyclohexane+ DES and toluene+n-heptane+DES,were studied by the liquid-liquid extraction.The experimental results show that the DES with N-formyl morpholine showed better extraction efficiency than that with others.The C2py-NFM was chosen for the separation of aromatic from alkane mixtures.The liquid-liquid extraction equilibrium can be obtained in ten minutes.The ratio of the DESs to system solution were set to 1:1.The best extraction efficiency was obtained at low temperature(20?)and low aromatics concentration system.For the benzene-cyclohexane system,the distribution coefficient of benzene(Dben),the distribution coefficient of cyclohexane(Dcyc)and the selectivity(S)can reach 1.73,0.06 and 23.8.For toluene-n-heptane system,the values of toluene(Dtol),n-heptane(Dhep)and selectivity(S)could be reached,0.88,0.02 and 40.7.Finally,the stability of C2py-NFM was investigated by recycling.The Othmer-Tobias equation was used to test the reliability of the liquid-liquid equilibrium(LLE)data.The calculation results showed that the liquid-liquid equilibrium data had a strong correlation.The experimental LLE data were correlated using the NRTL model,from the NRTL parameters(?gij and aij).As can be seen from the root mean square deviation(?x)of the LLE data,the calculated data is highly correlated with the experimental data.In order to increase the distribution coefficient,the DES with N-formylmorpholine(NFM)and 1-butyl-3 methyl bromide imidazole(BmimBr),was synthesized.The effects of extraction temperature,extraction time and the amount of eutectic solvent on the extraction were investigated.For the benzene-cyclohexane system,the distribution coefficient of benzene(Dben),the distribution coefficient of cyclohexane(Dcyc)and the selectivity(S)can reach 2.03,0.12 and 17.7.For toluene-n-heptane system,the values of toluene(Dtol),n-heptane(Dhep)and selectivity(S)could be reached,0.95,0.03 and 24.4.After 8 regenerations,the extraction performance was basically unchanged,indicating that BmimBr-NFM can be used to extract aromatic hydrocarbons and alkanes.The Othmer-Tobias equation was used to test the reliability of the liquid-liquid equilibrium(LLE)data.The calculation results showed that the liquid-liquid equilibrium data had a strong correlation.The experimental LLE data were correlated using the NRTL model,from the NRTL parameters(?gij and ?ij).As can be seen from the root mean square deviation(?x)of the LLE data,the calculated data is highly correlated with the experimental data.These studies have effectively improved for the separation of aromatic hydrocarbon and alkane and have a good guiding role for industrial applications. |
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