Sieving of Hydrogen-Containing Gas Mixtures with Tetrahydrofuran Hydrate

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 t...