LAUSR

Amines are incorporated into various membranes to improve their CO 2 separation performance. With amine-containing polymeric membranes, gas transport properties are often enhanced under humidity, where CO 2 migrates through the membranes in the form of bicarbonate ions. Piperazine (Pz) and its derivatives are known to catalyze the conversion of CO 2 to bicarbonate ions and have been used in liquid amine scrubbing technology. Piperazines were immobilized in poly(vinyl alcohol) (PVA), and the resulting polymeric membranes showed high CO 2 separation performance over H 2 and CH 4 . The gas transport properties were dependent on the chemical structure of the amines. In particular, 3-(1-piperazinyl)-1,2-propanediol (PzPD)-containing polymeric membranes gave excellent CO 2 separation performance, and the CO 2 permeability and CO 2 selectivity over CH 4 were 1060 Barrer and 370, respectively, at 50 °C and 90% relative humidity with a transmembrane CO 2 pressure of 11 kPa. The interaction between PzPD and CO 2 was quantitatively studied by inverse-gate decoupling 13 C NMR spectroscopy. CO 2 interacted with the secondary amino group on the Pz ring to form a carbamate, which was readily hydrolyzed to produce bicarbonate ions. The hydroxyl group on the C2 carbon of PzPD facilitated the interaction between CO 2 and the amine through hydrogen bonding, resulting in enhanced diffusivity of CO 2 in the membranes. Piperazine and its derivatives were incorporated into a thin film of poly(vinyl alcohol), and the CO 2 separation performance of the resulting amin-containing membranes was investigated. The gas transport properties were dependent on the chemical structure of the amines. In particular, 3-(1-piperazinyl)-1,2-propanediol (PzPD)-containing polymeric membranes gave excellent CO 2 separation properties over H 2 and CH 4 under humidity. CO 2 interacted with the secondary amino group on the Pz ring to form a carbamate, which was readily hydrolyzed to produce bicarbonate ions. CO 2 migrates through the membrane in the form of bicarbonate ions.