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Sieving of Hydrogen-Containing Gas Mixtures with Tetrahydrofuran Hydrate C

Zhong, Jin-Rong, Chen, Li-Tao, Liu, Tong-Cheng, Zeng, Xin-Yang, Sun, Yi-Fei, Sun, Chang-Yu, Liu, Bei, Chen, Guang-Jin, Ripmeester, John A.
Journal of physical chemistry 2017 v.121 no.50 pp. 27822-27829
Raman spectroscopy, carbon dioxide, crystals, diffusivity, hydrogen, methane, monitoring, sieving, tetrahydrofuran
Using the different diffusion rates of gas mixture components in hydrate crystals is a promising new method for the separation of gas mixtures. The diffusion behavior of hydrogen (H₂), methane (CH₄), and carbon dioxide (CO₂) in tetrahydrofuran (THF) hydrate was investigated experimentally by exposing a THF hydrate layer to H₂, H₂ + CH₄, or H₂ + CO₂ gas or gas mixtures and monitoring the penetration of the molecules into the hydrate by Raman spectra. The experimental results demonstrate that only H₂ molecules can penetrate the entire 5 mm thick hydrate layer, while the THF hydrate is resistant to CH₄ and CO₂ molecules on the experimental time scale employed. The minimum partial pressure for H₂ to diffuse through the THF layer is 2.9 MPa, and the diffusion coefficient of H₂ in the THF hydrate layer was determined to be 6.1 × 10–¹² m²/s via time-resolved Raman collection. This is the first observation of the sieving behavior of a massive hydrate layer toward different gas molecules. This work also suggests that Raman spectroscopy is an effective method for investigating molecular diffusion in hydrate or other media. Our findings are of significance for both hydrogen separation from gas mixtures and/or its storage in clathrate hydrates.