Efficient continuous SF₆/N₂ separation using low-cost and robust metal-organic frameworks composites.

Area of Science:

• Materials Science
• Environmental Science
• Chemical Engineering

Background:

• Physisorption is a viable alternative to cryogenic distillation for sulfur hexafluoride (SF₆) capture.
• Existing adsorbents struggle to meet industrial demands for SF₆ recovery.

Purpose of the Study:

• To develop low-cost composite adsorbents and an innovative Vacuum Temperature Swing Adsorption (VTSA) process.
• To achieve ultra-efficient recovery of low-concentration SF₆ from nitrogen (N₂).

Main Methods:

• Systematic investigation of in-pore chemistry and industrial process design.
• Construction of Al(fum)@2%HPC and Al(fum)@5%Kaolin composite pellets.
• Application of a two-stage VTSA process in fixed-bed adsorption-desorption experiments.

Main Results:

• Achieved record selectivities (>2×10⁴) and SF₆ dynamic capacities (~2.7 mmol/g).
• Demonstrated high SF₆ productivities (~58.7 L/kg), yields (~96.8%), and recyclability (~1000 cycles).
• Attained 99.91% SF₆ recovery with 99.91% purity and 2.1 mmol/g working capacity.

Conclusions:

• The developed VTSA process with composite pellets meets environmental and operational requirements for SF₆ recovery.
• Outperformed industrial zeolite 13X and significantly reduced energy consumption compared to cryogenic distillation.
• Revealed multi-site binding and ultra-fast diffusion mechanisms via advanced characterization and simulations.