Energy-saving extractive distillation processes design and optimization for the separation of ethyl acetate and n-heptane azeotrope

•Novel and energy-saving heat pump assisted extractive distillation processes are designed to separate EA-HEP azeotrope.•The σ-profile analyzes the intermolecular interaction at the molecular level.•The sequential iteration method is used to optimize the processes and get the minimum TAC.•The TAC, energy consumption and CO2 emission of HPED-WITH process decreases by 16.78 %, 28.14 % and 41.83 %, respectively. In the pharmaceutical and fine chemical industries, azeotropic mixtures like ethyl acetate (EA) and n-hexane (HEP) are produced. Effective separation and purification are essential for recycling resources and protecting the environment. This study investigates the design and optimization of energy-efficient extractive distillation processes for separating EA and HEP. N-methylpyrrolidone (NMP) and p-xylene (PX) were selected as extractants. Their effectiveness was validated through vapor liquid equilibrium (VLE) studies, and their interaction mechanisms were clarified using σ-profile analysis. Extractive distillation processes using NMP and PX as extractants (ED-NMP and ED-PX) were developed and evaluated based on total annual cost (TAC), energy consumption, and CO2 emissions. The results showed that the ED-PX process outperformed the ED-NMP process. Additionally, integrating a heat pump with an overhead steam preheater further enhanced all performance metrics, reducing TAC, energy consumption, and CO2 emissions by 16.78 %, 28.12 %, and 41.83 %, respectively. This study provides valuable insights for the separation and purification of EA and HEP.