Separation on Aromatics and Non-aromatics by Extractive Distillation with NMP

Abstract

Vapor-liquid-equilibrium (VLE) at normal pressure for the system formed by n-heptane, benzene and N-methyl-pyrrolidone (NMP) are investigated. The results show that NMP is a good extractive solvent that reverses the volatility of the binary system of n-heptane + benzene. A UNIFAC model is selected and proved that the group interaction parameters are reliable. A modified extractive distillation (MED) process, in which a little of water is added to lower the boiling point of reboilers in aromatics recovery column, is proposed on the basis of the original extractive distillation (OED) process. The process simulation shows that the proposed process raises the yield ratio of benzene from 94.2% to 98.2%. Since the modification is not complicated, the MED process have a lasting value in industry.