(351y) Amine-Containing CO2-Selective Membrane and Process for Carbon Capture from Flue Gas

Large-scale application of membrane in post-combustion carbon capture has been limited by the trade-off between CO₂ permeance and CO₂/N₂ selectivity of most polymeric membrane materials. In order to overcome this limitation, research efforts on facilitated transport membrane (FTM) have been devised with the objectives of (1) developing carriers with high CO₂ loading capacity and reactive diffusivity, and (2) designing membrane processes that can capitalize on the outstanding selectivity shown by FTM. In this presentation, a novel FTM was synthesized in a composite membrane configuration with a 170-nm selective layer coated on a nanoporous support. In the selective layer, polyvinylamine was used as fixed-site carrier and an amino acid salt, synthesized by deprotonating sarcosine with 2-(1-piperazinyl)ethylamine, was blended as mobile carrier. The membrane was used to fabricate 1.4-m² spiral-wound modules, which exhibited a CO₂ permeance of 1450 GPU and a CO₂/N₂ selectivity of 185 at 67°C with actual flue gas at the National Carbon Capture Center in Wilsonville, AL, USA.

In addition, for the range of CO₂ partial pressure relevant to carbon capture from coal-derived flue gas, significant increase in CO₂ permeance can be achieved upon the bulk removal of CO₂. For instance, at 67°C, the CO₂ permeance can increase from 1464 to 1918 GPU when the CO₂ partial pressure reduces from 74.1 to 3.9 kPa. Such a carrier saturation phenomenon has been modeled and incorporated into a two-stage membrane process featuring partial retentate recycle. It has been demonstrated that the bulk CO₂ removal reduces the CO₂ partial pressure gradually in the membrane module. This feature mitigates the carrier saturation and results in an uprising CO₂ permeance upon the CO₂ removal. For the membrane performance at 67°C, an attractive capture cost of $41.75/tonne can be achieved for 90% CO₂ capture in addition to offering the reduced system footprint.