Thermodynamic Mechanism-Based Sustainable Intensification Separation of n-Propyl Acetate/n-Propanol Using Ionic Liquid

In industrial synthesis, n-propyl acetate (NPAC) readily forms an azeotrope with n-propanol (NPA), making effective separation via conventional distillation difficult. To address the challenge of NPAC/NPA separation in chemical production, this study used COSMO-RS to identify 1-hexyl-3-methylimidazole acetate as an entrainer. The separation mechanism of the extractive distillation process was elucidated using quantum chemical analysis and molecular dynamics simulations. Based on this, an ionic liquid extractive distillation process was designed, and four thermally coupled process flows were developed to reduce energy consumption. Through a comprehensive evaluation of economic factors, acid gas emissions, energy consumption, and exergy losses, the ionic liquid heat-integrated vapor recompression heat pump and intermediate reboiler-assisted extractive distillation process (IL-HI-VRHP-IR) was identified as the optimal solution. Compared to the IL process, this process reduces total annual cost by 11.55%, acid gas emissions by 58.00%, and total energy consumption by 69.67%, while also minimizing exergy losses. It demonstrates excellent economic and environmental performance and provides important theoretical guidance for the development of separation technologies for the NPA/NPAC azeotropic system.