Facilitated transport membranes with an amino acid salt for highly efficient CO2 separation

An amino acid salt is selected as an effective carrier and is introduced into polymer matrix to fabricate facilitated transport membranes for enhancing CO2 separation performance. In this research, a series of Pebax (R) MH 1657 (Pebax (R)) membranes containing sodium glycine (SG) are fabricated. The Pebax (R)-SG membranes show higher CO2 permeability and CO2/gas selectivity than pure Pebax (R) membrane. The introduced SG plays two crucial roles in membranes. On one hand, SG provides simultaneously abundant amino groups (-NH2) and carboxylate groups (- COO-) as carriers for facilitating CO2 transport, imparting an enhanced CO2 separation performance via a facilitated transport mechanism. On the other hand, the addition of SG increases the total amount of absorbed water, resulting in the swelling of membrane matrix and the increase of CO2 solubility. In particular, CO2 permeability increases almost linearly with the increase of water content in membranes. As a consequence, the as-prepared Pebax (R)-SG-15 membrane shows the highest CO2 permeability of 1023 Barrer, CO2/CH4 ideal selectivity of 46 (separation factor of 43) and CO2/N-2 ideal selectivity of 91 (separation factor of 84) at 2 bar and 25 degrees C, supassing the 2008 Robeson upper bound line. All ideal selectivites are higher than their coresponding separation factors. The membranes containing amino acid salt show a potential application for CO2 separation.