Energy-saving extractive distillation system using o-xylene as an entrainer for the high-purity separation of dimethyl carbonate/methanol azeotrope

The pressure-swing distillation traditionally used in the industry for separating dimethyl carbonate/methanol (DMC/MeOH) commonly suffers from high energy consumption and challenges in achieving high-purity separation due to the existence of pinch zone. Hence, energy-saving extractive distillation system is explored to achieve the high-purity separation of DMC/MeOH azeotrope. With the analyses of isovolatility and residue curve maps based on Wilson model calibrated by vapor–liquid equilibrium experimental data, an extractive distillation process using O-Xylene (OX) as the most suitable entrainer were modeled and validated by using extractive distillation experiment. Furthermore, the design, optimization, and comparison of a 10000 t/a DMC extractive distillation process and a pressure-swing distillation process are investigated. It is demonstrated that the extractive distillation process presents significant economic and emission advantage, specifically with 34.66 % and 26.95 % reductions in operating cost (OC) and in total annual cost (TAC) respectively, as well as 42.53 % reduction in CO2 emissions. This work should provide a feasible and promising approach to energy saving, low-carbon, and high-purity separation of DMC/MeOH azeotrope.