Interfacially polymerized layers for oxygen enrichment: a method to overcome Robeson's upper-bound limit

Area of Science:

• Materials Science
• Chemical Engineering
• Polymer Chemistry

Background:

• Thin-film composite membranes are crucial for gas separation.
• Optimizing monomer selection and polymerization is key to enhancing membrane performance.
• Existing membranes face limitations in achieving high gas permeance and selectivity simultaneously.

Purpose of the Study:

• To optimize interfacial polymerization for advanced O2/N2 separation membranes.
• To investigate the impact of monomer structure and reactivity on membrane properties.
• To develop a thin-film composite membrane exceeding the upper-bound limit of conventional membranes.

Main Methods:

• Interfacial polymerization using aqueous phase monomers (diethylenetriamine, m-phenylenediamine, melamine, piperazine) and organic phase monomers (trimethyl chloride, cyanuric chloride).
• Controlled variation of monomer concentrations, polymerization time, and aqueous/organic monomer ratios (1.9-2.7).
• Strategic selection of monomers with specific numbers of reactive groups and structural arrangements (planar vs. linear/semirigid).

Main Results:

• Achieved a uniformly polymerized layer by controlling the aqueous/organic monomer ratio.
• Identified the need for monomers with three reactive groups for highly cross-linked layers.
• Demonstrated that semirigid monomers minimize structural defects while planar monomers increase them.
• Developed a membrane using trimethyl chloride and piperazine with O2/N2 selectivity of 10.43 and gas permeance of 7.72 × 10(-6) cm(3) (STP) s(-1) cm(-2) cm Hg(-1).

Conclusions:

• Monomer structure, reactivity, and polymerization conditions significantly influence O2/N2 separation performance.
• Combining planar and semirigid monomers (TMC and PIP) yields superior membrane properties.
• The developed membrane surpasses the upper-bound limit of conventional thin-film composite membranes for O2/N2 separation.