Gas separation properties of poly(amide-6-b-ethylene oxide)/amino modified multi-walled carbon nanotubes mixed matrix membranes

Amino modified multi-walled carbon nanotubes (MWNTs-NH2) were incorporated into poly(amide-6-b-ethylene oxide) (Pebax 1657) to prepare mixed matrix membranes (MMMs). The permeation properties of CO2, N2, CH4 and H2 were studied and the physical properties of Pebax/MWNTs-NH2 MMMs were characterized by X-ray diffractometer (XRD), Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). The incorporation of MWNTs-NH2 increased the amorphous region of Pebax phase in Pebax/MWNTs-NH2 MMMs, which was beneficial for the improvement of gas permeabilities. The apparent activation energy for permeation (Ep) for CO2 decreased with the increase of pressure, while those for N2, CH4 and H2 almost did not change. The Ep for CO2, N2, CH4 and H2 slightly decreased with the incorporation of MWNTs-NH2. Compared with pristine Pebax membrane, CO2 permeability increased almost 3 times for Pebax/MWNTs-NH2 MMMs with 33 wt% MWNTs-NH2. With the increase of MWNTs-NH2 content, the normalized permeabilities of N2, CH4 and CO2 showed almost the same increment and the selectivities of CO2/N2, CO2/H2 and CO2/CH4 remained constant, which were consistent with the Maxwell model prediction. Thus, the incorporation of MWNTs-NH2 significantly improved the gas permeation properties of Pebax/MWNTs-NH2 MMMs.