Interfacially-confined polyetherimide tubular membranes for H2, CO2 and N2 separations

Capturing CO2 and H2 purification from gas mixtures such as CO2/N2 and H2/N2 are vital in addressing greenhouse gas emission abatement and global energy strategy. Here, we present a systematic investigation of tubular polyetherimide (PEI) membranes prepared by combining dip-coating and multilayer assembly techniques to target CO2 and H2 transports and CO2/N2 and H2/N2 selectivities. The effects of deposition cycle during dipcoating on H2, CO2 and N2 single gas permeations and binary gas separations were evaluated. The membranes prepared by three deposited layers produced gas permeances (10-12 mol m- 2 s- 1 Pa-1) of 310, 150 and 1 for H2, CO2 and N2 respectively, corresponding to CO2/N2 and H2/N2 permselectivities of 149 and 308. For binary gas mixture separation, an exclusive 100% CO2 and H2 permeate purity was observed irrespective of feed gas concentration. The PEI membrane exhibited a suppression of glass transition temperature and crystallinity compared to the bulk polymer indicating interfacial confinement phenomenon, which was further confirmed by X-ray diffraction and Raman spectroscopic analyses. Due to a subtle change of imide group conformation of the obtained membrane layer, it was inferred that an increase in the polymer amorphicity and interfacial confinement facilitated the exclusive H2 and CO2 transports without much affecting the N2 permeance.

Automated summary

This study investigates the application of tubular polyetherimide (PEI) membranes prepared by dip-coating and multilayer assembly techniques in CO2 and H2 transport and CO2/N2 and H2/N2 selectivity. The results show that the permeability and selectivity of the membranes depend on the deposition cycle during dip-coating. For binary gas mixture separation, 100% CO2 and H2 purity is achieved regardless of the feed gas concentration. The PEI membrane exhibits interfacial confinement phenomenon, and the subtle change in imide group conformation contributes to increased polymer amorphicity and exclusive H2 and CO2 transport.