| dc.description.abstract | A great amount of anthropogenic CO2 emissions has caused the greenhouse effect which impacts the living environment of creatures on the planet. Effective carbon capture technologies need to be developed to reduce CO2 emissions. Membrane separation technology can be applied in carbon capture due to its advantages in energy conservation and pollution prevention. Poly(ether block amide)-based (PEBAX 1657) composite membranes were developed for carbon capture in separating CO2/N2, CO2/CH4, and CO2/H2 mixtures in this study.
Polyvinylamine/PEBAX (PVAm/PEBAX) blend membranes were prepared for carbon capture by a solution casting method. The presence of PVAm enhanced membrane hydrophilicity and gas solubility. When the mass ratio of PVAm to PEBAX reached 0.025, the blend membrane showed a CO2 permeability of 600 Barrer at 298 K and a feed gas pressure of 400 kPa, while the CO2/N2, CO2/CH4, and CO2/H2 ideal gas selectivity remained comparable with pristine PEBAX membrane.
Diethanolamine/PVAm/PEBAX (DEA/PVAm/PEBAX) composite membranes were fabricated on polysulfone substrate membranes. The structures of the composite membranes not only improved gas permeance due to reducing the thickness of the permselective layer but also provided great mechanical strength. DEA can increase membrane hydrophilicity. The DEA/PVAm/PEBAX composite membrane with a mass fraction of DEA in the membrane of 0.2 exhibited a CO2 permeance of 12.5 GPU which was higher than the PEBAX composite membrane (6.24 GPU). The CO2/N2, CO2/CH4, and CO2/H2 selectivity was 42.3, 22.9, and 12.1 at room temperature and 700 kPa.
NH4F/PEBAX membranes were developed by a solution casting method. The introduction of F- affected the permeabilities of N2, CH4, and H2 in the membranes more significantly than CO2 permeability due to the salting-out effect. On the other hand, F- made water molecules more basic owing to the hydrogen bonds, which was more favorable for CO2 dissolution in the membranes. Compared to pristine PEBAX membrane, the selectivities CO2/N2, CO2/CH4, and CO2/H2 in the NH4F/PEBAX(0.1) membrane were 54%, 13%, and 22% higher, respectively, and the CO2 permeability was 372 Barrer at room temperature and 700 kPa.
Mixed matrix membranes were fabricated by embedding amino-modified multi-walled carbon nanotubes (MWCNTs) as a dispersed phase in a PEBAX polymer matrix. After acid treatment, MWCNTs were modified by polydopamine (PDA) through self-polymerization of dopamine (DA). The catechol groups can react with amine groups on branched polyethylenimine (PEI) by the Michael addition reaction and Schiff base reaction. The addition of MWCNT-PDA-PEI can facilitate CO2 transport and adjust membrane structures. When the mass ratio of MWCNTPDA-PEI to PEBAX was 0.08, the CO2 permeability of the prepared MMM was 2.4-fold of that of the PEBAX membrane, while the selectivities of CO2/N2, CO2/CH4, and CO2/H2 at room temperature and 300 kPa were 107, 26, and 11, respectively. | en |
