Facilitated transport membranes containing amino-functionalized multi-walled carbon nanotubes for high-pressure CO2 separations

In the present work, high-performance mixed matrix membranes containing amines have been developed for effective CO2 removal at high pressures (15–28 bar) and high temperatures (103–121 °C). The membrane was synthesized by compatibly embedding amino-functionalized multi-walled carbon nanotubes (AF-MWNTs) as mechanical reinforcing fillers in the crosslinked polyvinylalcohol-polysiloxane/amine blend. The surface functionalization of MWNTs allows strong coupling with the hydrophilic membrane matrix to form a nano-reinforced facilitated transport membrane, which achieved exceptional CO2 selectivity and permeability via the facilitated transport mechanism as well as attractive membrane stability via the incorporation of MWNTs. The synthesized membranes exhibited an average CO2 permeability of 957 Barrers coupled with high selectivities vs. H2 (56), CH4 (264), and N2 (384) at 107 °C and 15 bar. The effects of AF-MWNT loading, high molecular weight species content, selective layer thickness, feed pressure, relative humidity, and temperature on membrane performance were thoroughly studied for a fundamental understanding of membrane properties. Furthermore, a mathematical model has been used to describe and explain the thickness-dependent CO2 transport behavior in the membrane. The combination of high CO2 permeability and good selectivities vs. CH4, H2, and N2, along with enhanced mechanical stability, makes the membrane a promising candidate for the gas separation applications at high pressures.