A Molecular Lubrication Strategy Enabled by Propane Impurity for Self-Enhancing Its Kinetic Separation in MOFs with...

Area of Science:

• Materials Science
• Chemical Engineering
• Separation Science

Background:

• Separating light alkanes like methane, ethane, and propane is difficult due to their similar properties.
• Existing methods struggle with the efficient removal of trace alkane impurities.

Purpose of the Study:

• To develop a novel self-boosting kinetic separation process for trace alkane removal.
• To utilize a molecular lubrication strategy within a tailored metal-organic framework (MOF).

Main Methods:

• In situ synchrotron X-ray diffraction (XRD) and Density Functional Theory (DFT) calculations.
• Molecular simulations to analyze propane diffusion within a Fe-based MOF.
• Breakthrough experiments using a simulated natural gas mixture.
• Six-bed vacuum pressure-swing adsorption (VPSA) simulations.

Main Results:

• Propane acts as a dynamic lubricant, smoothing diffusion pathways and lowering energy barriers in the MOF.
• A volcano-shaped pressure dependence of diffusivity was observed, with an optimum at approximately 5 kPa.
• Methane purity of ≥99.99% was achieved in breakthrough experiments.
• VPSA simulations predicted high methane recovery (80.4%) and purity (≥99.95%).

Conclusions:

• The molecular lubrication strategy effectively enhances kinetic separation of alkanes.
• Tailored MOFs with bottleneck pore structures can leverage trace impurities for improved gas separation.
• This approach offers a promising pathway for efficient natural gas purification.