CO₂ Transport Behavior in Perfluoropolyether Elastomers for Gas Separation Applications.

Area of Science:

• Materials Science
• Chemical Engineering
• Polymer Science

Background:

• Fluoropolymer membranes are vital for gas separation due to chemical stability.
• A key challenge is the permeability-selectivity trade-off, limiting CO2 capture and natural gas purification.
• Perfluoropolyether (PFPE) elastomers offer high permeability but require performance enhancement.

Purpose of the Study:

• To investigate CO2 transport in PFPE elastomers and their silica composites.
• To understand how silica incorporation impacts CO2 permeability, diffusivity, and solubility.
• To determine if silica fillers can overcome the permeability-selectivity trade-off in PFPE membranes for CO2/N2 separation.

Main Methods:

• Time-resolved attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) was used to quantify CO2 transport.
• Quartz crystal microbalance (QCM) was employed to measure CO2 sorption.
• Systematic examination of CO2 diffusion and solubility in neat PFPE and silica-filled PFPE composites.

Main Results:

• Neat PFPE elastomer exhibited high CO2 permeability (1218 Barrer) and low glass transition temperature (-52 °C).
• Silica incorporation (8.5 wt %) increased CO2 sorption capacity by 21% (15.10 to 18.35 mg/g·atm).
• CO2/N2 selectivity improved from 5.8 to 7.2 with only a 4.4% decrease in CO2 permeability (1164 Barrer).

Conclusions:

• Silica nanoparticles enhance CO2 sorption via interfacial free volume.
• Increased membrane tortuosity due to silica preferentially hinders N2 diffusion, improving selectivity.
• Silica-filled PFPE elastomers present a promising strategy for efficient CO2/N2 separation membranes.