| Abstract: | When raised to temperatures above the ice melting point, gas hydrates release their gas in well-defined, reproducible events that occur within self-maintained temperature ranges slightly below the ice point. This behavior is observed for structure I (carbon dioxide, methane) and structure II gas hydrates (methane-ethane, and propane), including those formed with either H2O- or D2O-host frameworks, and dissociated at either ambient or elevated pressure conditions. We hypothesize that at temperatures above the H2O (or D2O) melting point: (1) hydrate dissociation produces water + gas instead of ice + gas, (2) the endothermic dissociation reaction lowers the temperature of the sample, causing the water product to freeze, (3) this phase transition buffers the sample temperatures within a narrow temperature range just below the ice point until dissociation goes to completion, and (4) the temperature depression below the pure ice melting point correlates with the average rate of dissociation and arises from solution of the hydrate-forming gas, released by dissociation, in the water phase at elevated concentrations. In addition, for hydrate that is partially dissociated to ice + gas at lower temperatures and then heated to temperatures above the ice point, all remaining hydrate dissociates to gas + liquid water as existing barriers to dissociation disappear. The enhanced dissociation rates at warmer temperatures are probably associated with faster gas transport pathways arising from the formation of water product. |
| Genre: | Article |
| ProdID: | 70027229 |
| Citation Author: | Circone, S.; Stern, L. A.; Kirby, S. H. |
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| Citation End Page: | 5755 |
| Citation Issue: | 18 |
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| Citation Language: | English |
| Citation Larger Work Title: | Journal of Physical Chemistry B |
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| Citation Number Of Pages: | 9 |
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| Citation Search Results Text: | The role of water in gas hydrate dissociation; 2004; Article; Journal; Journal of Physical Chemistry B; Circone, S.; Stern, L. A.; Kirby, S. H. |
| Citation Start Page: | 5747 |
| Citation Volume: | 108 |
| Citation Year: | 2004 |
| Type: | citation/reference |
| Text: | The role of water in gas hydrate dissociation; 2004; Article; Journal; Journal of Physical Chemistry B; Circone, S.; Stern, L. A.; Kirby, S. H. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Thu, 1 Jan 2004 00:00 -0600 |
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