Energy-efficient separation of propylene/propane by introducing a tailor-made ionic liquid solvent

In the petrochemical industry, the separation of propylene/propane is usually paid much attention due to its high energy-consuming and environmental challenges. In this work, an energy-efficient extractive distillation (ED) separation process of propylene/propane is proposed by introducing a tailor-made ionic liquid (IL) solvent. The structure optimization of ILs is performed with a novel design objective in the computer-aided ionic liquid design (CAILD) method. By solving a formulated CAILD-based mixed-integer nonlinear programming (MINLP) problem, the ethylimidazolium ethyl sulfate ([C₂IM][EtSO₄]) is identified as the best IL solvent. The separation performance of [C₂IM][EtSO₄] in the ED process of propylene/propane is then evaluated through rigorous process simulation in Aspen Plus. For comparison, the conventional separation process of propane/propylene is also simulated and optimized. Based on the optimized operations, in-depth energy and economic assessment are conducted for an industrial-scale separation of propane/propylene in a Chinese refining industry. Remarkably, the [C₂IM][EtSO₄]-based ED process has 68.9% energy savings and 74.7% cost reduction when compared to the conventional process.