Ag-Functionalized Carbon Molecular-Sieve Membranes Based on Polyelectrolyte/Polyimide Blend Precursors

We prepared dense flat-sheet Ag-functionalized carbon molecular-sieve (CMS) membranes from blends of P84 co-polyimide and a sulfonated poly(ether ether ketone) with a Ag+ counterion (AgSPEEK). These blends offer the possibility of producing new functionalized precursor structures, which were previously not possible, such As integrally skinned asymmetric hollow fibers. Membranes prepared at a pyrolysis end temperature of 800degreesC showed a maximum permeability for all tested gases at a Ag content of approximately 2.5 wt.-% (He permeability P-He = 465 Barrer (1 Barrer = 7.5 x 10(-18) m(2) s(-1) Pa-1), P-CO2 = 366 Barrer, P-O2 = 91.8 Barrer, P-N2 = 10.3 Barrer). The maximum achieved selectivity for O-2 over N-2 with CMS membranes based on these blends was alpha(O2)/(N2) = 13.5 (Ag content: 4.5 wt.-%, P-O2 = 52.7 Barrer). The CO2 over N-2 selectivity reached a value of 48.9 (Ag content: 4.5 wt.-%, P-CO2 = 191 Barrer). These observations are explained by the formation of selective bypasses around Ag nanoclusters in the CMS matrix.