CO2-Selective Membranes Containing Amino or Ethylene Oxide Groups for Carbon Capture from Flue Gas

This presentation covers two types of CO₂-selective membranes for carbon capture from flue gas: (1) amine-based membranes and (2) ethylene oxide (EO)-based membranes.  The former is based on the facilitated transport mechanism, while the latter is based on the solution-diffusion transport mechanism.  For the membranes containing amino groups, a high-molecular-weight of polyamine was successfully synthesized.  Different selected aminoacid salts were incorporated into the polyamine solution for membrane preparation.  The polyamine served as a fixed carrier, and the amino acid salts acted as mobile carriers.  The amine-containing membranes showed a CO₂ permeance of more than 1100 GPU and a CO₂/N₂ selectivity of at least 200 at 57ºC.  For the membranes containing EO groups, we have synthesized membranes with polyamide-polyethylene oxide (PA-PEO) copolymer blended with polyethylene glycol dimethyl ether (PEG-DME) or polyethylene glycol (PEG).  We have also synthesized a polydimethylsiloxane (PDMS) membrane reproducibly with a very high CO₂ permeance, which can be used as a caulking layer for our thin membranes.  The membrane containing EO groups we synthesized was SO₂-insensitive but had a low CO₂/N₂ selectivity.  The resulting membranes showed a CO₂ permeance of 940 GPU and a CO₂/N₂ selectivity of 25 at 57ºC.  The syntheses and transport properties of the membranes will be presented.  The effects of different aminoacid salt mobile carriers, EO-containing small molecules and membrane thicknesses on the membrane transport performance will be discussed.  We are continuing to improve the transport performance of both types of CO₂-selective membranes.