Extractant Screening Of LTTMs And Phase Equilibrium Study For Benzene-Cyclohexane System

Benzene and cyclohexane are important chemical raw materials.Because they have similar boiling points,similar structures and are easy to form azeotrope,they can not be separated by traditional distillation technology.Therefore,the separation is considered to be one of the most challenging separation processes in the field of petrochemical industry.Because of the low energy consumption,liquid-liquid extraction is considered to be the most promising method for separation of benzene and cyclohexane,and solvent selection is the key to the extraction process.The suitable LTTMs are screened from 25 kinds of hydrogen bond donors and 13 kinds of hydrogen bond acceptors using COSMO-SAC software,as the new green solvent to separate benzene and cyclohexane.The optimum solvent selected is sulfolane+tetrabutylammonium bromid,and the molar ratio is 5:1.In order to compare the extraction performance,another group of LTTMs ethylene glycol+trimethylamine hydrochloride is also screened.Then the ternary liquid-liquid equilibrium data of benzene-cyclohexane-LTTMs is measured,and the effects of mole ratio of different hydrogen bond acceptors and hydrogen bond donors(3:1,5:1 and 7:1)and different temperatures(30,40 and 50 ?)on the extraction performance are explored.The experimental results show that the extraction performance of sulfolane+tetrabutylammonium bromid is better than ethylene glycol+trimethylamine hydrochloride,which is consistent with the COSMO-SAC calculation;when molar ratio of sulfolane and tetrabutylammonium bromid is 5:1,the extraction performance is the highest at 50?;when the mass fraction of benzene is lower than 0.3,the influence of temperature on the extraction performance is not obvious.The activity coefficient model NRTL is used to correlate the liquid-liquid equilibrium data and then obtained two interaction parameters.The root mean square deviation(RMSD)is used to analysis the calculated values and the experimental values,the results show that the calculated values are in good agreement with the experimental data,the experimental data are accurate and reliable,and the NRTL model can well fit with the experimental data.The Aspen Plus software is used to simulate the extraction process of benzene-cyclohexane,and the operating conditions are designed and optimized.Then compared with the traditional extraction processes using sulfolane as solvent,and the economic evaluation is calculated,the results show that the extraction performance of LTTMs is better than that of sulfolane,and the total annual cost saves 56.51%.Therefore,LTTMs can be used as alternative solvents for extraction and separation of benzene-cyclohexane.