Separation Of Acetone And Methanol By Extractive Distillation With Salt And Solvent As Entrainer

Acetone and methanol are both basic materials and reagents often used in chemical industry. Normally,4 tons of food are consumed to produce 1 ton of acetone by cereals fermentation. Meanwhile, methanol can only be obtained under high temperature and high pressure. Acetone and methanol are therefore expensive. In furfural production, acetone and methanol are two main products in the exhaust gases. Important application prospects with reducing the environmental pollution and creating economic benefits can be anticipated if acetone and methanol are separated effectively and recycled.Extractive distillation is the traditional method to separate acetone-methanol azeotropic mixture with disadvantadges such as large solvent ratio and impurity of product resulted from the volatility of solvent. The extractive distillation with the combination of liquid solvent and solid salt as the separating agent, which eliminates the disadvantages of both extractive distillation and salt distillation, and retains the advantages of them, has attracted much resaerch interests. Here, extractive distillation with solvent and salt mixture as the separating agent was applied to separate acetone-methanol azeotropic mixture.The poupose of this work is to optimize the processses of separation of acetone-methanol mixture by salt extractive distillation. The choice of solvent is one of the key procedures. Water, DMSO, ethylene glycol and EMA are better solvents for obtaining acetone top product, since their polarity are larger than methanol, based on the principle of dissolution in similar structure. It is also demonstrated from the residue curve maps that water, DMSO, ethylene glycol and EMA are the suitable solvents to separate acetone and methanol. Simulation results show that water and DMSO can both eliminate acetone-methanol azeotrope, while the other two solvents can not. Water is thus the best choice by consideration of its separation ability, price and so on. On the basis of experience, theory, as well as the experimental results, salts were selected in this study. Mg(NO3)2+Ca(NO3)2, MgCl2+CaCl2 are optimized salts for separation.The operation parameters play an important role on the separating effect. When water+ Mg(NO3)2+Ca(NO3)2 was employed as separation agents, the optimized operation parameters are as follows:the time of total reflux is 25min, reflux rate is 5:1, the salt water density is 6.25%, the mass ratio of Mg(NO3)2 to Ca(NO3)2 is 1:1, and the velocity of solvent is 2mL/min. On employing water+MgCl2+CaCl2 as separation agents, the optimized operation parameters are as follows:total reflux time is 50min, reflux rate is 5:1, salt water density is 7.08%, mass ratio of MgCl2 to CaCl2 is 1:1, and the velocity solvent is 2mL/min.The research results in this study reveal that the optimized separtion agent is the mixture of double salt and solvent, which is superior to pure solvent and solvent/single salt systems. The optimized processes of double salt extractive distillation was demonstrated in separation of acetone-methanol azeotropic mixture with high efficiency.