(397e) Ultra-High H2/CO2 Separation Factors in Carbon Molecular Sieve Membranes Derived from an Aromatic Polyamide

Hydrogen (H­₂) is a clean energy carrier mainly produced by natural gas reforming with CO₂ byproduct. Economical H₂/CO₂ separation is important in blue hydrogen production for simultaneous H₂ purification and CO₂ capture. Membrane separation is an energy-efficient and cost-effective alternative to pressure swing adsorption and amine absorption. Membranes with highly attractive H₂/CO₂ separation factors are required to produce high-purity H₂. Carbon molecular sieves (CMS) membranes are highly promising for H₂/CO₂ separation. Recently, we reported novel solution-processable aromatic polyamide (aramid)-derived CMS hollow fiber membranes with highly attractive H₂/CO₂ ideal selectivity above 360.¹

In this talk, we will report ultra-high H₂/CO₂ mixture separation performance in aramid-derived CMS hollow fiber membranes with finely tuned ultramicropores. By controlling pyrolysis variables, we obtained aramid-derived CMS hollow fiber membranes with H₂/CO₂ separation factor over 1000. To our best knowledge, this is among the highest H₂/CO₂ separation factors reported in semi-permeable membranes. The effects of operating conditions such as feed pressure, feed composition, feed moisture, and permeation temperature on the H₂/CO₂ mixture separation performance will be presented. We hypothesize that highly-refined ultramicropores were responsible for the unprecedented H₂/CO₂ mixture separation factor in these aramid-derived CMS membranes. We found that conventional pore size measurement methods were unable to characterize these highly-refined ultramicropores. We will discuss a novel approach to characterize the pore size distributions of carbon membranes with highly-refined ultramicropores.

Reference:

1. Iyer, G. M.; Zhang, C., Precise Hydrogen Sieving by Carbon Molecular Sieve Membranes Derived from Solution-Processable Aromatic Polyamides. ACS Materials Letters 2023, 5, 243-248.