TRANSPORT-PROPERTIES OF CARBON-DIOXIDE THROUGH AMINE FUNCTIONALIZED CARRIER MEMBRANES

CO2 facilitated transport was studied using a membrane with amine site s covalently bound to the polymer backbone and ion exchange membranes which have amine complexing agents (carrier) as counterions. The two t ypes of membranes were compared, and several amine functionalities for the ion-exchange membrane were studied. Although the covalently bonde d membranes had a larger absorption capacity than amine functionalized Nafion ion-exchange membranes, the facilitation effect of CO2 through the covalently bonded membrane was very small (less than 1.5 at 10 kP a CO2 partial pressure) compared with the ion-exchange membrane (8.0 a t 11 kPa CO2 pressure with mono protonated ethylenediamine carrier for m in Nafion 117). A simulation model for the covalently bound membrane s was developed to understand the results. The facilitation effect dep ends largely on carrier diffusivity, and reactive diffusion through th e covalently bonded membrane is much slower than counterion diffusivit y through the ion-exchange membrane. The ethylenediamine carrier exhib ited a large facilitation effect in a Nafion 117 membrane. Other secon dary or hindered diamines exhibited a small facilitation effect. For a swollen Nafion membrane, both ethylenediamine and ethylenediamine der ivatives showed a high facilitation effect, and a secondary diamine pr oduced a facilitation factor of 4.09 and a CO2 flux of 1.02 x 10(-8) m ol/cm(2) s at 22.5 kPa CO2 pressure in the feed.