(659f) Investigating PIM-Type Polymeric Membranes for CCS Under Relevant Industrial Conditions

An attractive type of membrane material for CCS applications are polymers with intrinsic microporosity (PIMs) – forming flexible and easy-to-manufacture single-component membranes with high gas permeabilities and selectivity for CO₂ over N₂ and O₂ – primary components of flue gas. In this work, a novel membrane analyzer was developed to observe the multi-component permeation of flue gas constituents through membranes of PIM-1 and its more hydrophilic carboxylate functionalized version, cPIM-1, to reveal the impact of contaminants and industrial process conditions on the membrane separation efficiency.

Humidity was first introduced to the membranes for 3 hours, followed by 10% CO₂ in N₂ whilst maintaining the selected humidity. The permeation curves were measured using CO₂ and humidity probes at the inlet and outlet, with nitrogen measured using a TCD.

The carboxylated PIM-1, cPIM-1, was studied under the same conditions as PIM-1. The carboxylation is known to make the cPIM-1 membrane more hydrophilic and thus the effect of increasing relative humidity was found to be more pronounced, with a 40% decrease in CO₂ permeation observed in cPIM-1 compared to the 20% decrease observed for PIM-1. The CO₂/N₂ selectivity of cPIM-1 was found to decrease by 20% over the same humidity range. Separate water permeation studies found that the behavior of the cPIM-1 membrane when exposed to water was opposite to that behavior of PIM-1 owing to the hydrophilicity of cPIM-1, with the water permeation and diffusion constant increasing with relative humidity.

Further studies were undertaken using Dynamic Vapor Sorption (DVS) to confirm the membrane uptake behavior, most importantly that of water in the Langmuir voids ^[1,2] of the polymers and the subsequent impact of this water build-up on CO₂ uptake.

References

1. E. Lasseuguette, M.-C. Ferrari, S. Brandani, Energy Procedia, 2014, 63, 194-201.
2. P. Li, T. S. Chung, D. R. Paul, Journal of Membrane Science, 2014, 450, 380-388.