Molecular mechanism-based extractant screening and process design for the separation of methanol/dimethyl carbonate azeotrope

Abstract

The separation of methanol/dimethyl carbonate azeotrope is an important process in the industrial production of dimethyl carbonate. Extractive distillation is an effective separation method, which can ensure the full utilization of resources and achieve sustainable development. In this work, an extractant screening method based on density functional theory (DFT) was proposed. By comparing the interaction energy difference, the optimal extractant (dimethyl sulfoxide, DMSO) was obtained. The molecular mechanism of action between the extractant and the separated components was explained. The separation order of the components of the extraction distillation process was obtained by the magnitude of the interaction energy. The σ-profile curve and isovolatility curves method were used to verify the effectiveness of the proposed method. A new separation process with DMSO as an extractant was designed. With the lowest total annual cost (TAC) as the goal, sensitivity analysis and cyclic iteration method is used to optimize the parameters involved in the process to determine the best process parameters. Heat integration technology is introduced to further reduce energy consumption. TAC, energy utilization efficiency, and global warming potential (GWP) were used to evaluate the process. Compared with the reported optimal extractant methyl salicylate, the TAC of the simple process using DMSO as the extractant was reduced by 9.08%. The heat-integrated process with DMSO shows a TAC reduction of 17.17% compared to the simple process. And the energy utilization efficiency and GWP were increased by 40.90% and decreased by 31.88%, respectively. The results show that the extractant screened by DFT method is applied to the azeotrope separation, which makes the process have good economic benefits, low energy consumption, and less environmental impact.