(585k) Block-Copolymer Derived Nanoporous Carbon Membranes for High Throughput Gas Separation

Authors: 
Agrawal, K. V., University of Minnesota
Ultrathin, gas-selective membranes are highly desired to reduce the total area for a given membrane operation, reducing capital and operating costs, as well as production time and complexity for a potential scale-up. Moreover, such membranes are expected to increase the overall energy-efficiency.

Nanoporous carbon films can be obtained by pyrolysis of block-copolymer thin films. However, for their application in high permeance membrane, a crack-free synthesis on a macroporous support is not trivial. Herein, a gas-selective nanoporous carbon (NPC) membrane is reported1 which displayed a gigantic hydrogen permeance (5.9 million GPU) that is several orders of magnitude higher than the membranes in the literature (barring the bilayer graphene membrane reported by Celebi et al.).2 A moderate H2/CO2 ideal selectivity of 4.3 was obtained.

A defect-free, ultra-high flux nanoporous carbon film was synthesized by optimizing the synthesis and transfer protocols. SEM and TEM images reveal the crack-free mesoporous structure with an average pore size of 20 ± 16 nm. Permeances of He and CH4 were tested at 25 °C and at 100 °C, whereas H2, N2 and CO2 were tested in the temperature range of 25-300 °C. NPC exhibited an extremely high permeance (above 1 million GPU) for all the gases. The gas permeance scaled inversely to square root of molecular weight in the temperature range of 25-250 °C, confirming Knudsen transport regime attributed to the mesoporous structure of the NPC film.

The NPC film was stable up to a transmembrane pressure of 4 bar. XPS data confirmed that NPC film primarily consisted of C-C bonded structure (284.8 eV), with only a small contribution of C-O bonds (286.7 eV), which typically arise from the C-O-C and C-OH groups on the surface of the film.

The ultrahigh hydrogen permeance (5.9 GPU), a moderate gas selectivity (H2/CO2 ideal selectivity of 4.3) and a high temperature stability (250 °C) make NPC film highly attractive in separation of gases.

References

1. Dakhchoune M. et. al, Patent Application, PCT/EP2017/057684

2. Celebi, K. et. al, Science. 344, 289-292 (2014)