Separation of gas product mixtures from CO2 electrolysis by chabazite zeolite hollow fiber membranes

Electrolysis of carbon capture liquids is extensively studied for production of commodity chemicals such as ethylene and syngas coupled with near neutral carbon emissions. The cathode product consists of complex gas mixtures whose separation remains a major bottleneck, owing largely to the limited selectivity of electrocatalysts. This study proposes a cost-effective and energy-efficient solution for downstream separations from CO 2 RR electrolyzers. We investigate high–silica chabazite zeolite (CHA) hollow fiber membranes (ZHFMs) as a separation platform for gas mixtures relevant to (bi)carbonate electrolysis due to their superior molecular sieving capabilities and high surface-to-volume ratios. We evaluated membrane performance at 25–150 ° ⁢ C with different gas compositions and sweep gas flow rates (0–200 sccm). Single component gas permeation data were used to parameterize a Maxwell-Stefan modeling framework, enabling semi–quantitative prediction of multicomponent permeation behavior. The calibrated model was employed to examine the influence of operating variables such as temperature, pressure, and feed composition on separation performance and gas recovery. To demonstrate reproducibility, 10 successive batches of ZHFMs were synthesized, and the single component H 2 /C 2 H 4 selectivity was found to be 49 ± 5 on a random sample from each batch. We tested scalability, onset of temperature fatigue, and long-term stability to evaluate membrane robustness, with consistently good performance demonstrated across multiple cycles. A multi-fiber module was developed and operated without use of sweep gas, emulating typical industrial conditions. The module maintained excellent H 2 permeance (∼1000 GPU) and H 2 /C 2 H 4 separation factor ∼ 30 over 100 h in a simulated multi-component feed representative of the gas phase cathode product.