Separation Of Water-Ethanol-Isobuthanol System By Extraction Distillation

Isobutanol is a commonly used organic synthetic raw material,widely used in many fields such as medicine,food and chemical industry.However,in the process of industrial production of isobutanol,industrial waste water containing ethanol and isobutanol will be produced,and the separation of water-ethanol-isobutanol system is proposed.In this paper,different solvents were used to extract and rectify the water-ethanol-isobutanol system.The vapor-liquid equilibrium data of water+ethanol+isobutanol+solvent was determined.The NRTL equation related experimental data was selected to establish a thermodynamic model to describe the vapor-liquid equilibrium behavior of the system.The separation performance of different extractants on water-ethanol-isobutanol system was compared.The use of Aspen software to select the appropriate extractant for process simulation provides guidance for industrial separation.Under normal pressure,the vapor-liquid equilibrium data of the quaternary systems of water?1?+ethanol?2?+isobutanol?3?+ethylene glycol?4?system and water?1?+ethanol?2?+isobutanol?3?+glycerol?4?were measured in this paper,the activity coefficient and relative volatility of the corresponding components were obtained.We use the NRTL equation for data correlation.For the water?1?+ethanol?2?+isobutanol?3?+ethylene glycol?4?system,the temperature and meteorological composition deviations are?T=0.1491 K,?y₁=0.0008,?y₂=0.0032,?y₃=0.0036,for water?1?+ethanol?2?+isobutanol?3?+glycerol?4?system,they are?T=0.2169 K,?y₁=0.0006,?y₂=0.0023,?y₃=0.0024.The experimental results and calculation results are in good agreement,indicating that the NRTL model is reliable enough to describe the phase equilibrium behavior.The eutectic solvent used as an extractant for system separation has shown good effect.In this paper,the use of glycerin+choline chloride as the extractant compared with glycerin alone,with the addition of choline chloride,the activity coefficient of water continues to decrease and the activity coefficients of ethanol and isobutanol continue to increase,which makes the the relative volatility of ethanol to water and the relative volatility of isobutanol to water are increasing.The increase of the relative volatility of ethanol to water and the increase of the relative volatility of isobutanol to water are beneficial to dehydration.A strict equilibrium plate model is used to simulate the extractive distillation process.The water,ethanol and isobutanol mass fractions were set to 0.0176,0.6395,0.3429,and the mixed solution with a total flow rate of 1000 kg·h^-1 was used as the separation object.Separation target is to make the mass purity of ethanol and isobutanol reach 99.9%and 99.7%respectively,and the recovery rate reaches 99.7%.The eutectic solvent glycerin+choline chloride 2:1 and glycerin were used as the extractants.The degree coefficient model uses the binary interaction parameters optimized by the experimental data as the model parameters,and the Aspen Plus chemical simulation software is used to simulate and optimize the extractive distillation process of the water-ethanol-isobutanol system.The simulation results show that,under the condition of ensuring the same number of theoretical plates,feed position,and reflux ratio,using glycerin+choline chloride 2:1 as the extractant is better than glycerin only,which achieves a better separation effect.From the perspective of the separation performance of the extractant and economic and environmental protection,the eutectic solvent glycerol+choline chloride 2:1 for the water-ethanol-isobutanol system by extractive distillation is better.This paper provides reliable experimental data and theoretical basis for the application of eutectic solvent in the separation of water-ethanol-isobutanol system.