Structure-Controlled Polyetherimide Hollow Fibers for Biogas Purification

Area of Science:

• Membrane science and technology
• Chemical engineering
• Materials science

Background:

• Biogas purification is crucial for renewable energy production.
• Polyetherimide (PEI) hollow-fiber membranes offer potential for gas separation.
• Controlling membrane morphology and defects is key to improving separation performance.

Purpose of the Study:

• To develop PEI hollow-fiber membranes for biogas purification.
• To investigate the relationship between spinning conditions, membrane morphology, and gas transport properties.
• To evaluate the impact of silicone post-treatment on membrane performance and biogas upgrading.

Main Methods:

• Hollow fibers were fabricated from PEI using dimethylformamide (DMF) and N-methyl-2-pyrrolidone (NMP) as solvents.
• Membranes underwent post-treatment with silicone solutions of varying concentrations.
• Scanning Electron Microscopy (SEM) was used to analyze membrane morphology.
• Gas permeance and selectivity were measured using mixed gases.
• A membrane module was tested under quasi-real biogas upgrading conditions.

Main Results:

• DMF-based fibers showed a more macrovoid-rich structure, leading to higher permeance but lower selectivity compared to NMP-based fibers.
• Silicone post-treatment significantly improved selectivity, with 3 wt.% silicone being more effective.
• The optimized membranes achieved high CO2 and H2S permeances with good selectivity for CO2/CH4, H2S/CH4, and CO2/N2.
• Biogas upgrading experiments demonstrated efficient methane enrichment up to 96 mol.% and significant CO2 reduction.

Conclusions:

• Controlling the spinning process and applying silicone post-treatment are effective strategies for enhancing PEI hollow-fiber membrane performance.
• These membranes are suitable for simultaneous methane enrichment and acid gas removal in biogas upgrading.
• The developed membranes offer a promising solution for efficient biogas purification.