(699g) CO2 Selective Membranes Composed of Linear and Branched Polyethers

Membranes could be an integral part of the pre-combustion and post-combustion capture of CO₂ during the process of coal gasification/water-gas-shift reaction which transforms coal, oxygen and water feed streams into hydrogen for fuel and CO₂ for sequestration. The objective of this work is to design polymeric membranes that have very high CO₂ permeability and high selectivity toward CO₂ (i.e. very low H₂ and N₂ permeability).  It is our hypothesis that the favorable thermodynamic interactions that enable certain polymers to dissolve in dense CO₂ at extremely high pressure will also allow membranes composed of these polymers to exhibit high CO₂ permeability at low pressure. Candidates include supported liquid membranes composed of poly(ethylene glycol) (PEG), linear and branched poly(propylene glycol)(PPG), linear and branched poly(butylenes glycol)(PBG) and the rubbery membranes composed of the crosslinked analogs of the liquid polymers. These polymers constitute the most CO₂-philic polymers that have been identified to date.  Results of mixed gas permeability and selectivity values for CO₂/H₂ and CO₂/N₂ gas pairs will be discussed.

For the supported liquid membranes, PEGDME has shown the best performance in terms of CO₂ permeability and selectivity over H₂. For the crosslinked membranes, the linear poly(tetramethylene glycol) (PTMEGDA) had the best performance with a CO₂ permeability.