Oxygen-18 enrichment in the water of a clathrate hydrate

Capture of carbon dioxide from flue or fuel gas mixtures by clathrate crystallization in a silica gel column

“…The hydration number is the number of water molecules per guest molecule. It can be determined experimentally by simultaneously using powder X-ray diffraction and Raman spectroscopy on solid hydrate phase Kumar et al, 2008;Sum et al, 1997;Susilo et al, 2007a;Uchida et al, 1999;Udachin et al, 2007Udachin et al, , 2001 or by solid state NMR spectroscopy (Davidson et al, 1983;Ripmeester and Ratcliffe, 1988). In the presence of THF, the conversion of water to hydrate is determined by the next equation…”

Isotopic Composition of Interstitial Fluids and Origin of Methane in Slope Sediment of the Middle America Trench, Deep Sea Drilling Project Leg 84

“…The pore-water δ 18 θ analyses reported in Table 1 and shown in Figure 3 for samples from Holes 568 and 570 confirm the Leg 67 observations. The water molecules that form the solid clathrate hydrate are known to exclude salts and concentrate 18 O, relative to the coexisting liquid water (Davidson et al, 1983 The question of what happens to the salts and 18 Odepleted H 2 O excluded during gas hydrate formation has not been resolved, but loss to overlying seawater or adjacent sediments seems to be required. An earlier interpretation (Hesse and Harrison, 1981) was that the gas hydrate probably is in contact with pore water of normal salinity and δ 18 θ.…”

Leg 164 Introduction

“…The velocities range from 2.4 to 3.8 km/s (Stoll et al, 1971;Stoll and Bryan, 1979;Davidson et al, 1983;Pandit and King, 1982). However, all these measurements have been made on systems containing pure propane and ethane gas hydrates (structure II), which may not be representative of methane gas hydrate (structure I).…”

“…During the formation of gas hydrate, the heavy molecules of water (H 2 18 O or DH 16 O) preferentially concentrate in the gas hydrate lattice while the isotopically lighter molecules of water (H 2 16 O) remain in the residual water (Davidson et al, 1983). This phenomenon has been employed to explain (1) deep-sea sediment cores that contain water with higher δ 18 θ content and lower salinities than seawater as having been generated by the recent breakdown of gas hydrate (Hesse and Harrison, 1981;Harrison and Curiale, 1982;Matsumoto, 1989;Ussier and Paull, 1995) and (2) other pore waters from deeper cores that are isotopically light and saline as resulting from the expulsion of fluids during gas hydrate formation (Kvenvolden and Kastner, 1990).…”