Experiment And Simulation Of Extractive Distillation Process For Purifying Tetrahydrofuran

Tetrahydrofuran is an important organic solvent, and is widely used in the productionof synthetic resin, medicine, rubber and so on. Tetrahydrofuran forms minimumazeotrope with water, so it is impossible to obtain tetrahydrofuran with purity higherthan that of the azeotrope by general distillation. In this paper, a united process ofextractive and azeotropic distillation for separating tetrahydrofuran-water mixture waspresented. Ethylene glycol was chosen as the extractant, and extractive distillationwas used to separate the mixture, while azeotropic distillation was used to give theproduct a further dehydration to obtain product with higher purity. Product of thisprocess has comparable purity to product of pressure swing distillation, which ishigher than that of traditional process of extractive distillation with two columns.In this paper, firstly we used the theory of hydrogen bond to choose possibleextractant for the mixture, adopting the modified UNIFAC model to calculate theactivity coefficient of tetrahydrofuran and water at the presence of extractant, andobtained the relative volatility. Taking both the calculated results and literature datainto account, we chose ethylene glycol as the proper extractant.Secondly, continuous distillation was chosen to carry on the dehydratingexperiment of tetrahydrofuran. The influences of different parameters in extractiveand azeotropic distillation were studied, and product with water content lower than5.000E-4was obtained.Lastly, RadFrac module in Aspen Plus was selected to simulate the unitedprocess of extractive and azeotropic distillation, choosing Wilson model forseparating tetrahydrofuran-water mixture. Through simulation, influences ofparameters to separation were studied, and the best parameters of process wereconfirmed after optimization, achieving energy conservation. Technical process wasclosed, and the product could achieve a purity of99.95%. The yield oftetrahydrofuran is up to99.88%, and0.11g ethylene glycol is consumed for everykilogram tetrahydrofuran product.