Impact of feed composition on performance of PDMS nanomembrane-based multistage CO2 capture

Carbon dioxide removal is necessary to mitigate the impacts of anthropogenic emissions. Membrane-based CO 2 capture approaches offer portability, scalability, and tunability advantages over sorption-based processes. We developed a benchtop CO 2 capture testbed to experimentally approximate the multistage behavior of a single 200 cm 2 plate-and-frame PDMS nanomembrane module, using a custom feed gas blending station to set each stage's feed composition and estimate multistage performance sequentially. We used this testbed to study the impact of feed composition with respect to CO 2 (0.044% to 10.0%), O 2 (~1% to ~20%), and N 2 on CO 2 capture performance to produce feed streams suitable for subsequent electrochemical CO 2 reduction ([CO 2 ] ≥ 40%). We show that decreasing the O 2 feed concentration by 95% significantly improves performance by reducing the number of required stages to reach [CO 2 ] ≥ 40% by one (for feeds of 1.0% ≤ [CO 2 ] ≤ 5.0%) or two (for feeds of [CO 2 ] < 1.0%). This influence is weaker for CO 2 -rich feeds ([CO 2 ] > 5.0%). These experimental outcomes were corroborated by process simulations. While most prior studies of membrane-based CO 2 capture have focused exclusively on the separation of CO 2 and N 2 , we show conclusively that high O 2 feed content critically impacts CO 2 capture performance and should be considered in system design and technoeconomic analysis. This proof-of-concept study exemplifies the need to emphasize CO 2 /O 2 selectivity as a figure of merit for new membrane materials. Using O 2 removal as a feed pretreatment method may enable nanomembrane-based CO 2 capture from more dilute sources with inexpensive commercial polymers ( e.g. , PDMS) and thus accelerate technological development for sustainable chemical manufacturing using CO 2 . • PDMS nanomembranes offer high CO 2 permeance and sufficient CO 2 selectivity for efficient portable and low-hazard CO 2 capture. • Removing O 2 from CO 2 -lean feeds improves the ability of subsequent stages to further concentrate CO 2 . • The number of stages required to generate CO 2 -rich streams suitable for electrochemical CO 2 conversion depends strongly on the O 2 content of the feed. • Feed composition across four orders of magnitudes, and not permeance which is constant, determines CO 2 recovery rates.