Economic evaluation of hybrid ZIF-8-based membranes and distillation process for propylene/propane separation

The total annual cost (TAC) of propylene and propane separation through existing distillation processes is extremely expensive due to their similar physical and chemical properties. The hybrid process of membrane and distillation is the most promising approach to address this challenge. However, the TAC of the hybrid process is largely affected by its membrane material properties including separation performance and area as well as its configuration such as connection mode. Herein, we developed a tubular membrane separation model that features the introduction of a pressure change from the feed side to the retentate side. The hybrid process of membrane separation and distillation was further developed. The TAC of the hybrid process was continuously reduced by adjusting the membrane parameters (ZIF-8 membrane, ZIF-8 MMMs) and the connection mode (one-step and two-step) based on this model. The two-step hybrid process significantly reduces the TAC, with a maximum reduction of 41.55 % compared to conventional distillation. In addition, it enhances both separation efficiency and economic performance, as reflected by a 63.12 % decrease in energy consumption, a 53.8 % improvement in energy efficiency, and a 48.68 % reduction in CO₂ emissions, demonstrating strong potential for industrial application.