Hydroxy-Functionalized PAMAM Dendrimer as a CO₂-Selective Molecular Gate for CO₂ Membrane Separation

Abstract

Two hydroxy-functionalized PAMAM Dendrimers (3OH-PAMAM and 4OH-PAMAM) were developed as immobilized liquid membranes (ILMs) to separate CO2 from a mixture of CO2 and N2. The hydroxy-functionalized PAMAM demonstrated excellent properties of CO2-selective separative material for CO2 membrane separation. The hydroxy-functionalized PAMAM dendrimers displayed greater water sorption and more CO2 separation properties than that of conventional PAMAM without hydroxy groups. The resulting ILMs of 4OH-PAMAM showed the highest CO2 over N2 selectivity of 7000 and above with CO2 permeance of 1.1×10−11 m3 (STP) m−2 s−1 Pa−1 (1.5 GPU, 1 GPU = 7.5 × 10−12 m3 (STP) m−2 s−1 Pa−1), with a membrane thickness of 100µm (CO2 permeability 147 Barrers), at 9.7 kPa CO2 partial under 130 kPa feed pressure with 80% RH at 40 °C. For the ILMs of dendrimers at over 60%RH, their PCO2 – α plots exceeded the upper bound line by Roberson in 2008 and that is a potential for CO2 separation from the gas mixture.