Mechanism research and process design for the separation of dimethyl carbonate and n-propanol by extractive distillation using ionic liquid

For the separation of azeotropes, extractive distillation (ED) stands out as one of the most potent methods available, and the screening of the extractant is a crucial step. Within this work, an initial screening of potential extractants was conducted using the COSMO model, and the extraction capabilities of the extractants were compared through quantum chemistry (QC) calculations, the result revealed that [EMim][DEP] exhibited the strongest extraction capacity. Subsequently, the VLE data of DMC-NPA-[EMim][DEP]/DMSO/EG/[EMim][BF₄] were obtained at 101.32 kPa. The extraction mechanism of the extractant was elucidated through molecular dynamics (MD) simulation. Finally, the separation process was designed using Aspen Plus with [EMim][DEP] and DMSO as the extractant respectively, and multi-objective optimization was carried out for the two processes, the ED process using [EMim][DEP] as the extractant has a lower TAC and gas emissions, which is more valuable for application. Furthermore, heat integration was carried out on the ED process, the results demonstrate that the TAC has dropped to 1.1306 × 10⁶ $/Y, and the gas emissions have decreased to 1.6644 × 10³ kg/Y, which is reduced by 11.45% and 17.16%, respectively.