New sterically hindered polyvinylamine membranes for CO2 separation and capture

Facilitated transport membranes have been intensively studied for CO2 separation and capture, in which amine carriers are the key for membrane separation performance. It has been reported that sterically hindered amines possess superior CO2 loading capacity over unhindered amines. In this work, we successfully introduced the effect of the steric hindrance to the nitrogen site of amine into polyvinylamine membranes. Sterically hindered poly(N-vinylamine)s, namely poly(N-methyl-N-vinylamine), poly(N-isopropyl-N-vinylamine), and poly(N-tertiary-butyl-N-vinylamine), were synthesized from modifying unhindered poly(N-vinylamine). The effect of steric hindrance on membrane performance was investigated under the typical flue gas CO2 capture conditions, i.e., 57 °C and ~ 1 atm, showing that poly(N-methyl-N-vinylamine) was the one with the optimal steric hindrance degree for the best membrane performance. Compared with unmodified polyvinylamine, poly(N-methyl-N-vinylamine) demonstrated 24% improvement on CO2 permeability and 14% increase in CO2/N2 selectivity at 57 °C. The membrane performance enhancement by amine steric hindrance was found to be greatly influenced by temperature. At 102 °C, poly(N-methyl-N-vinylamine) demonstrated a CO2 permeability of 6804 Barrers, a CO2/N2 selectivity of 350, and a CO2/H2 selectivity of 162, which were approximately 4 times those of unmodified polyvinylamine. This work has extended the study on sterically hindered polyamines for CO2 facilitated transport and developed a next-generation fixed-site carrier membrane.