Effect of amine structure on CO<sub>2</sub> capture by polymeric membranes

<p>Poly(amidoamine)s (PAMAMs) incorporated into a cross-linked poly(ethylene glycol) exhibited excellent CO<sub>2</sub> separation properties over H<sub>2</sub>. However, the CO<sub>2</sub> permeability should be increased for practical applications. Monoethanolamine (MEA) used as a CO<sub>2</sub> determining agent in the current CO<sub>2</sub> capture technology at demonstration scale was readily immobilized in poly(vinyl alcohol) (PVA) matrix by solvent casting of aqueous mixture of PVA and the amine. The resulting polymeric membranes can be self-standing with the thickness above 3 μm and the amine fraction less than 80 wt%. The gas permeation properties were examined at 40 °C and under 80% relative humidity. The CO<sub>2</sub> separation performance increased with increase of the amine content in the polymeric membranes. When the amine fraction was 80 wt%, the CO<sub>2</sub> permeability coefficient of MEA containing membrane was 604 barrer with CO<sub>2</sub> selectivity of 58.5 over H<sub>2</sub>, which was much higher than the PAMAM membrane (83.7 barrer and 51.8, respectively) under the same operation conditions. On the other hand, ethylamine (EA) was also incorporated into PVA matrix to form a thin membrane. However, the resulting polymeric membranes exhibited slight CO<sub>2</sub>-selective gas permeation properties. The hydroxyl group of MEA was crucial for high CO<sub>2</sub> separation performance.</p>