Separation Of The Azeotrope Of 2-methyl-2-butanol-water By Liquidliquid Extraction + Azeotropic Distillation

2-methyl-2-butanol is an important chemical raw material,which can be widely used in synthetic perfumery,medicine and color film industries.It is also used as solvent,flotation agent and plasticizer.However,2-methyl-2-butanol and water form a minimum boiling point azeotrope during the production of 2-methyl-2-butanol.At present,there are few re-ports on the method of separation 2-methyl-2-butanol-water system.Because liquid-liquid extraction consumes less energy,the process of the liquid-liquid extraction+distillation is a promising method to separate 2-methyl-2-butanol-water system.The extractant is the key to the feasibility of this process,but the appropriate extractants and related liquid-liquid equilibrium data for this process are scarce in the literature.In this work,three solvents(cyclohexane,ethylbenzene and o-xylene)were selected as extractants to separate the sys-tem of 2-methyl-2-butanol-water by combining literature and practical experience.The three ternary systems of 2-methyl-2-butanol-water-cyclohexane/ethylbenzene/o-xylene were measured at 303.2,313.2 and 323.2 K under 101.3k Pa.The liquid-liquid equi-librium data were validated by the Othmer–Tobias and Hand equations,and the regression coefficients R~2 were all greater than 0.984.The NRTL and UNIQUAC thermodynamic mod-els were used to regress the measured liquid-liquid equilibrium data.And the binary inter-action parameters were obtained.After calculating the separation coefficient(D)and the separation factor(S),cyclohexane and o-xylene were chosen as extractants to separate the system of 2-methyl-2-butanol-water.The residual curve maps of 2-methyl-2-butanol-water-cyclohexane/o-xylene were used to analyze the feasibility of liquid-liquid extraction+azeotropic distillation process.Taking the total heat duty of reboilers as the objective function,a sequential iterative optimization-method was adopted to optimize each tower.Compared with the traditional azeotropic dis-tillation process,the new processes using cyclohexane and o-xylene as extractants reduce43.56%and 21.42%energy,respectively.Compared to the process using o-xylene as the extractant,the one using cyclohexane as the extractant saves 28.17%energy.