Helium (He) is a strategically scarce resource primarily occurring in helium-bearing natural gas. The generally low helium content in natural gas resources results in significant extraction challenges and high costs. Gas separation membrane technology offers an attractive opportunity for the cost-effective extraction of He from natural gas. Highly selective and permeable gas membranes are urgently needed to address the extremely low He concentration in natural gas mixtures. In this study, polysilsesquioxane (PSQ) membranes with ultramicropores (0.4–0.5 nm) were constructed via co -polymerization of an organic-rich precursor (bis3-(trimethoxysilyl)propylethylene diamine (BTPDA)) and another organic-lean precursor (1,2-bis(triethoxysilyl)ethane (BTESE)). Such a strategy led to the formation of a novel hybrid PSQ network structure, which possesses rigid network skeleton and flexible ultramicropores, allowing for the precise molecular sieving for separation of He from its mixtures. The resulted membranes displayed excellent structural stability, He permeability (>1570 GPU, measured with pure He) and He/CH 4 selectivity (>100) upon the optimization of the molar ratio of these two precursors during the sol-gel process. Compared to traditional PSQ membranes fabricated via homopolymerization of single precursor with either organic-rich or organic-lean properties, as well as other reported polymer and inorganic membranes, the membranes with tailored flexible ultramicropores tended to overcome the trade-off of He permeability and He/CH 4 selectivity, showing great promise for the industrial He extraction from natural gas field.
Lu Wang,Ying Li,Liming Pu,Miao Yang,Hongsheng Lu,Xuehong Gu,Xuerui Wang
Helium extraction from natural gas is energy extensive since >95% feed stream needs to be liquefied in multi-cycles. Membrane gas separation is an energy-efficient alternative because of room temperature operation and no phase change. However, the practical application is significantly retarded by the limited permeation flux, which is mainly attributed to the thick selective layer. Herein, asymmetric 6FDA-APAF 0.5 -Cardo 0.5 copolyimide membranes with effective thickness of ∼ 200 nm were prepared by the one-step phase inversion method. The He permeance reached up to 120 GPU, one order magnitude higher than that of the free-standing one. The selectivity was 44 for He/N 2 and 67 for He/CH 4 binary mixtures. The performance surpassed 2019 upper bound and the benchmark membranes for He separation from N 2 or CH 4 . Meanwhile, the performance is resistant to the impurities of C 2 H 6 and CO 2 in the natural gas. Together with long-term stability (>200 h), the thin 6FDA-APAF 0.5 -Cardo 0.5 membrane would pave the way to He extraction from natural gas for practical application.
危险品化学品经营许可证（带存储）