(353a) High Performance Polybenzimidazole-Derived Carbon Molecular Sieve Hollow Fiber Membranes for Gas Separations

There is renewed interest in sustainable hydrogen production and utilization as a pathway to eliminate all carbon emissions from energy industry. Hydrogen production from abundant (e.g. natural gas) or renewable (e.g. biomass) hydrocarbon fuels involves a separation step; to remove CO₂ and other impurities. The industry standard gas separation methods including pressure swing adsorption and solvent sorption has been practiced for H₂/CO₂ separations. Owing to disadvantages of industrial standard gas separation methods including high equipment cost, energy consumption, long start-up/shutdown time, and loss of efficiency in modular configurations, membrane technology has emerged as a promising alternative. However, the inherent bottleneck of simultaneously achieving high permeability and H₂/CO₂ selectivity is a challenge in commercial deployment of membrane technology. In this study, our approach is to employ strong size-sieving polymer, polybenzimidazole (PBI), to fabricate carbon molecular sieve (CMS) hollow fiber membranes (HFMs) having tailored ultra-micropores with enhanced the size-sieving abilities for exceptional gas separation permeance. The PBI-CMS membranes were tailored for gas separations by optimizing the effect of carbonization condition, and pre-carbonization chemistry tailoring and spatially controlled HFM modification. Results demonstrated substantially high H₂ permeance spanning two orders of magnitude (100 to 2000 GPU) and H₂/CO₂ selectivity ranging from 10 to 500 at elevated temperatures suitable for process intensification with the hydrocarbon derived clean hydrogen production process scheme. The influence of operating conditions and gas composition on the separation performance of PBI-CMS HFMs will be discussed to assess their practical applicability.