(70c) CO2-Selective Membranes Composed of Cross-Linked Polyethers

Membranes could be an integral part of the post-combustion capture of CO₂ from the effluent gas stream of coal-fired power plants.  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 and CO₂ selectivity at low pressure.  (These polymeric membranes have recently been assessed for the pre-combustion capture of CO₂ from a CO₂- and H₂-rich shifted gasifier stream).

The crosslinked polymeric membranes used in this study of post-combustion capture of CO₂ from a N₂-rich stream have been previously assessed and shown promise for the pre-combustion separation of CO₂ from a H₂-rich shifted fuel gas stream. Candidates include either (a) CO₂-philic polymers with linear repeat units such as poly(ethylene glycol) (PEG), polytrimethylene ether glycol (i.e. linear polypropyleneglycol), and polytetramethylene glycol ether (i.e. linear polybutylene glycol), or (b) CO₂-philic polymers with branched repeat units such as polypropyleneglycol and polybutylene glycol.  Results of mixed gas permeability and selectivity values for CO₂/N₂ gas pairs will be discussed, and the performance of membranes with linear and branched repeat units will be contrasted.