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Anomalous Self-Preservation of Surfactant-Derived Gas Hydrates at 1 Atm

Guochang Zhang and Rudy E. Rogers. Swalm School of Chemical Engineering, Mississippi State University, P.O.Box 9595, Mississippi State University, MS 39762

Gas hydrates are being considered to store and transport natural gas because of their unique high gas concentration and process safety. Recently, methane hydrates of structure I that were formed from melting-ice were reported to be self-preserved at 1 atm and within a temperature window between about 245 K and 270 K, a window is much higher than the equilibrium temperature of 193 K. However, this self-preservation behavior has been reported not to happen to natural gas hydrates of structure II. Our research group previously has shown and reported that that surfactants have been reported to promote gas hydrate formation. In this study, the dissociation and self-preservation behaviors at 1 atm of surfactant-prepared gas hydrates of both structure Ⅰand structure Ⅱwere investigated. The research found that when using surfactants both methane hydrates of structure I and natural gas hydrates of structure II have demonstrated super stability at one atm slightly below the freezing point of water. Furthermore, upon reducing the pressure to 1 atm, decomposition of hydrates is less than 2%. This value applies to methane hydrates as well as natural gas hydrates, whereas previous reports defined hydrate anomalous stability for only about 50% of fractional remnant mass of methane hydrates of structureⅠ. These results are quite encouraging for the technology of storage and transportation of natural gas in the form of solid hydrates, making the hydrate process more attractive and competitive for industry.