Simple lattice model explains equilibrium separation phenomena in glassy polymers.

Area of Science:

• Membrane science and technology
• Chemical engineering
• Materials science

Background:

• The Robeson bound is a theoretical limit for kinetics-driven gas separations.
• Sorption-driven membrane processes, such as CO2/N2 separation, lack a similar theoretical framework.
• Understanding limiting factors in sorption-driven separations is crucial for process optimization.

Purpose of the Study:

• To investigate the theoretical underpinnings of sorption-driven membrane separations.
• To identify and explain the factors controlling the limiting behavior in these processes.
• To differentiate between sorption and transport effects in gas separation performance.

Main Methods:

• Utilized a simple lattice model to simulate transport properties.
• Employed dynamic mean field theory for analysis.
• Examined disordered model structures to isolate sorption from kinetic effects.

Main Results:

• Transport effects significantly influence sorption-driven membrane processes.
• Perm-selectivity in these systems is consistently lower than sorption selectivity.
• Sorption selectivity represents an unattainable upper limit for performance.

Conclusions:

• Sorption-driven membrane separations are governed by both sorption and transport phenomena.
• The interplay of transport effects, arising from structural features, dictates achievable separation performance.
• A deeper understanding of transport mechanisms is key to designing efficient sorption-driven membranes.