Ionic Liquid-Assisted Extractive Distillation for Ethylene/Ethane Separation: Molecular Design and Process Assessment

In the petrochemical industry, the separation of ethylene and ethane is a crucial step in ethylene production due to its significant energy consumption, high costs, and environmental impact. This study proposes an extractive distillation (ED) method for ethylene/ethane separation incorporating a customized ionic liquid (IL) solvent as an extractant. The CAILD (computer-aided ionic liquid design) approach was used for solvent screening. By solving a formulated MINLP (mixed-integer nonlinear programming) problem based on CAILD, methylpyridinium trifluoroacetate ([C1Py][TFA]) and methylimidazolium trifluoroacetate ([C1Im][TFA]) (CAS number 104290-54-2) were identified as the optimal IL solvents. Subsequently, rigorous process simulations of IL-assisted ethylene/ethane separation were conducted with Aspen Plus. Finally, a comprehensive assessment covering energy, environmental, and economic aspects was performed. The results demonstrate that, compared to conventional separation processes, the [C1Py][TFA] and [C1Im][TFA]-assisted processes achieve total annual cost reductions of 46.51% and 69.82%, respectively. Additionally, energy consumption is decreased by 41.60% and 42.16%, leading to a reduction in greenhouse gas emissions by 34.00% and 34.65%, respectively.