Evaluation of the Permeation of Syngas and Its Components through a Synthesized Matrimid Asymmetric Hollow-Fiber Membrane

Bioconversion of syngas (H₂–CO–CO₂) to organics is an excellent means of carbon recycling. Membrane-based gas-delivery systems can overcome the challenge of syngas’s low solubility in water. However, to maintain syngas conversion stoichiometry, it is crucial to have a membrane that delivers gases at high rates without selectivity toward any component. We synthesized an asymmetric, high-flux, low-selectivity hollow-fiber membrane, “small-defect-engineered”, to prevent bubble formation in future bioreactors. We created six sets of Matrimid membranes and screened their He/N₂ selectivity and permeances. We compared the pressure-normalized flux of the set with the highest He/N₂ permeance against a commercial symmetric membrane for a syngas mixture and its individual purified components. Under equal pressure, the asymmetric membrane exhibited 300-fold higher H₂-flux, 80-fold higher CO-flux, and 100-fold higher CO₂-flux than the symmetric membrane for pure gases. For the mixture, the asymmetric membrane had a 45-fold greater H₂-flux, 100-fold greater CO-flux, and 400-fold greater CO₂-flux than those of the symmetric membrane. Although the asymmetric membrane’s selectivity (H₂:CO:CO₂, 1:5.2:12) exceeded that of the commercial membranes (1:3:1.7), the asymmetric membrane possesses highly desirable traits for bioconversion of syngas, as its gas fluxes greatly exceed those of commercial membranes.