[MIS21-P07] Carbon isotope fractionation of CO2 during the formation of clathrate hydrate
Keywords:gas hydrate, stable isotope, carbon dioxide, isotopic fractionation
Samples of CO2 hydrate (weight: 0.7 g) were experimentally prepared in a pressure cell (volume: 30 mL), and the temperature was controlled by a liquid bath (258-274 K) and cold rooms (226-254 K). Isotopic compositions of both residual and hydrate-bound CO2 were measured by an isotope ratio mass spectrometer (IRMS). Samples were formed in the temperature range from 226 K to 274 K. The carbon isotopic differences between hydrate-bound and residual CO2 distributed between 1.2‰ and 1.5‰, agreed fairly well with the previous report (Luzi et al., 2011). The difference seemed to be large (1.5-2.0 ‰) at 226 K, indicating that the equilibrium pressure of 13CO2 hydrate is slightly larger than that of 12CO2 hydrate, and the difference between them becomes large in lower temperature. We will show these equilibrium data for 13CO2 and 12CO2 hydrates and compare with the results in stable isotope.
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