(699f) Carbon Molecular Sieve Hollow Fiber Membranes with Ultra-High Hydrogen/Carbon Dioxide Selectivity

Over 90% of the world's hydrogen (H₂) is produced from fossil fuels such as natural gas and coal. For example, natural gas reforming is carried out by reacting high-temperature steam with methane to produce a syngas comprising hydrogen and carbon monoxide, which is further reacted in water-gas shift reactors to produce shifted syngas comprising hydrogen and carbon dioxide (CO₂). Separation of the H₂/CO₂ mixture is important to H₂ purification and carbon footprint reduction. This separation is known as one of the most challenging membrane gas separations because diffusion favors the smaller and less condensable H₂ while sorption favors the larger and more condensable CO₂. Also, membranes must provide stable separation performance under high-temperature and high-pressure shifted syngas conditions up to 250 °C and 10 bar.

In this talk, we will present novel carbon molecular sieve (CMS) hollow fiber membranes derived from an aromatic copolymer for decarbonized H₂/CO₂ separation. Defect-free precursor hollow fiber membranes were fabricated by solution spinning, which were pyrolyzed to provide CMS hollow fiber membranes. By tailoring pyrolysis conditions and CMS membrane ultramicropore structure, we obtained outstanding H₂/CO₂ separation performance in the CMS hollow fiber membranes. Under a simulated shifted syngas mixture at 200 °C and 10 bar, the novel CMS hollow fiber membranes showed ultra-high H₂/CO₂ separation factor above 500 with competitive H₂ permeability significantly above the polymer upper bound. Notably, the attractive separation performance was stable for at least ten days without reduction in permeability or separation factor. To our best knowledge, this represents the highest H₂/CO₂ separation factor obtained in sorption-diffusion membranes under aggressive shifted syngas conditions.