Polyvinylamine/amorphous metakaolin mixed-matrix composite membranes with facilitated transport carriers for highly efficient CO2/N2 separation

Abstract

In order to obtain high-performance facilitated transport membrane for CO2/N2 separation, we prepared mixed-matrix composite membranes (MMCMs) by polyvinylamine (PVAm) and the amorphous layered metakaolin (MK), with polysulfone (PSf) as a support. The attenuated total reflectance Fourier-transform infrared spectroscopy results revealed the strong interfacial interaction between the PVAm and the oxygen-rich MK. MK was homogenously dispersed in the PVAm matrix, as confirmed by scanning electron microscopy. The MMCMs showed the enhanced CO2 separation performance with a CO2 permeance of 152 GPU and a CO2/N2 selectivity of 78 at 1 bar under pure gas condition, when the MK loading was 1 wt%. These values were much higher than those of the PVAm membrane loaded with the crystalline multi-layer kaolin, with a CO2 permeance of 85 GPU and a CO2/N2 selectivity of 55. The enhanced separation performance is mainly ascribed to the increase of the intermolecular distance between the polymer chains after the addition of the MK sheets to the PVAm matrix, which was validated by X-ray diffraction. Moreover, the addition of the amorphous MK to PVAm can increase more tortuosity of gas transport than multi-layered and other shape fillers in the MMCMs as a result of the homogenous dispersion of the fully exfoliated MK in the membrane. Besides, the MMCMs exhibited excellent long-term stability performance even under mixed-gas conditions for over 300 h, with a CO2 permeance of 188 GPU and a CO2/N2 selectivity of 83.8, surpassing the Robeson's upper bound proposed in 2008.