Optimizing the cask effect in multicomponent natural gas purification to provide high methane productivity

The efficient separation of CH4 from natural gas containing C2H6 and C3H8 impurities is an important topic. Previous work on the separation of CH4/C2H6/C3H8 mixtures often focuses on the C3H8/CH4 selectivity, inadvertently sidelining the critical importance of C2H6/CH4 selectivity. This oversight results in reduced CH ₄ productivity and compromised separation efficiency, a phenomenon often termed as the cask effect. Herein, we fine-tune the interrelationship between thermodynamics and kinetics, targeting enhanced CH4 production. A synergistic thermodynamic-kinetic C3H8/CH4 and C2H6/CH4 selectivity is achieved using dynamic breakthrough experiments, underpinned by the stable metal-organic framework TIFSIX-Cu-TPA. The CH4 productivity in TIFSIX-Cu-TPA is up to 5 mmol g-1, surpassing most of the popular materials. Detailed density functional theory and molecular dynamics computational insights reveal a counteractive thermodynamic-kinetic relationship, proving pivotal for the simultaneous breakthrough of C2H6 and C3H8 under optimal conditions. Moreover, precise adsorption sites of C2H6 and C3H8 are clearly determined through in situ single-crystal structures.

Automated summary

Efficient separation of CH4 from natural gas containing C2H6 and C3H8 impurities is crucial. Previous studies focused on C3H8/CH4 selectivity while neglecting the importance of C2H6/CH4 selectivity, leading to decreased CH4 productivity and compromised separation efficiency. In this study, a synergistic thermodynamic-kinetic selectivity for C3H8/CH4 and C2H6/CH4 was achieved using TIFSIX-Cu-TPA, surpassing most popular materials. Computational insights revealed a counteractive thermodynamic-kinetic relationship and determined precise adsorption sites of C2H6 and C3H8.