Study On The Extractive Distillation Process Of Unsaturated And Saturated Alcohols

The separation of saturated and unsaturated alcohols with the same carbon number,is a rather difficult problem in chemical industrial,cause these systems usually have very similar boiling point,or will have azeotropic point.It is almost impossible to separate these systems by ordinary distillation.Instead,extractive distillation is a promising way to solve this problem.As an instance,the separation process of 3-methyl-3-buten-l-ol and 3-methyl-1-butanol using extractive distillation was discussed in this paper.Firstly,three kinds of extractants,ethylene glycol,strong polar solvent A and weak polar solvent B,are preliminarily screened on the basis of polarity and solubility.But since there were few reports in literature about the separation process of 3-methyl-3-buten-1-ol and 3-methyl-1-butanol,and lack of related vapor-liquid equilibrium(VLE)data,it is difficult to design and calculate the extractive distillation process accurately.In order to solve this problem,the two infinite dilution activity coefficients of two components solution system composed of 3-methyl-3-buten-1-ol or 3-methyl-1-butanol with extractant were measured by ebulliometry method.Using the estimation tool in Aspen Plus,the model parameters of NRTL activity coefficient model were calculated based on the measured infinite dilution activity coefficients,which made it possible to predict the VLE in the whole concentration range and to design the process of extractive distillation by Aspen Plus.At the same time,according to the measured infinite dilution activity coefficients,the infinite dilution selectivity of three extractants was calculated,then,extractants were further screened.Based on the above experiments and calculations,the extractive distillation process of 3-methyl-3-buten-1-ol and 3-methyl-1-butanol using solvent A or B as extractant was simulated by Aspen Plus.And according to the simulation results,it is found that the solvent B is more suitable as extractant.Using sensitivity tool,the process of extractive distillation using B as extractant was optimized,and ideal theoretical results were obtained.In addition,the extractive distillation was studied from engineering point of view.A function about the relationship between relative volatility,solvent ratio,reflux ratio and operation pressure was regressed.The regressed function,together with Fenske function and Gilliland correlation formula could indicate the influence of solvent ratio,reflux ratio,operation pressure and tray number on the separation results.Meanwhile,it also provides convenience for the application of the shortcut method in the design and calculation of extractive distillation.In this paper,the extractive distillation process of 3-methyl-3-buten-l-ol and 3-methyl-1-butanol is studied,but the research ideas and methods may have some references for the separation of similar systems.