Study On Separation Of Binary Azeotrope Methanol-Toluene

Methanol and toluene are important organic solvents which are widely used in thefield of pharmaceuticals, fine chemicals and so on. At the atmosphere pressure,methanol and toluene form azeotrope and their relative volatility is1, which can’t beseparated by conventional distillation.This paper studies the separation of such binary azeotrope by extractivedistillation using o-xylene as the solvent.First, vapor-liquid equilibrium curve of methanol-toluene was determined byexperiment. Combination of experimental and referenced data was used to verify thereliability of the vapor-liquid equilibrium device. Then o-xylene was chosen as thesolvent through the UNIFAC group contribution method and its effect was verified byvapor-liquid equilibrium experiment. Results show that o-xylene can increase therelative volatility significantly.Second, the small scale batch extractive distillation with constant reflux ratio(R=3)and continuous solvent feeding was carried out to separate methanol and toluene,when the solvent ratio is1, methanol product with a concentration of92.5%wt can begot at the top of the column and the recovery is73%.Finally，PRO/II and Aspen Plus were used to simulate the batch and continuousprocess respectively. Effects of reflux ratio, feed position of raw material and solvent,solvent flowrate and temperature on the product yield, operation time and purity wereanalyzed to get the optimal operation parameters. Results show that, during the batchprocess, when the number of the stages is25, the optimal reflux ratio is2, solventfeed position is4, solvent ratio is1:1, the methanol product has a mole purity of99%and the recovery is97.4%; during the continuous process, when the number of thestages is30, the optimal reflux ratio is2, solvent and original feed position are4and25, solvent ratio is1, the purity of the methanol product and o-xylene can reach99.4wt%and96wt%separately. These results can provide some reference for theindustrial production.