Techno-economic optimization of extractive distillation for propane-propylene separation: Evaluating conventional and ionic liquid entrainers

Propylene is a key raw material in the petrochemical industry, essential for producing polypropylene, styrene, resin, fiber, propylene glycol, and other chemicals. However, its separation from propane in propane-propylene mixtures remains a significant challenge due to their similar boiling points and physical properties. Conventional separation methods, including high-pressure and low-pressure distillation, suffer from high energy requirements and operational complexities. An extractive distillation column (EDC) presents a viable alternative by leveraging entrainers to enhance relative volatility, facilitating efficient separation. This study focuses on optimizing extractive distillation using various entrainers, including N-methyl-2-pyrrolidone (NMP), Acetonitrile (ACN), Triethylene glycol (TEG), and an Ionic liquid (IL), tetramethylammonium acetate (TMAA). A COSMO-RS screening approach was employed to identify suitable ILs. The ED process was simulated using Aspen Plus v.14, with results demonstrating that NMP achieved the highest separation efficiency, yielding 99.8% polymer-grade propylene and 95.9% propane. A techno-economic assessment revealed that NMP had the lowest total annual cost ($25.71 million), while ACN and ILs were economically unfeasible due to high material and energy costs. These findings highlight the potential of NMP-based EDC as a cost-effective solution for high-purity propylene production, paving the way for process optimizations to enhance sustainability and industrial viability.