Methane Hydrate© Patrice Bentham
Apr 27, 2001
Methane hydrate is one instance of a gas hydrate. Examples of other gases that can form hydrates include ethane, carbon dioxide, hydrogen sulfide and propane. What are hydrates? Should we be interested in them? Are they useful?
To understand what exactly a hydrate is, let's visit Hydrate.org, http://hydrate.org/intro.cfm . Their simple summary of hydrates states that hydrates are a natural formation containing large amount of methane and water in the form of ice. They are crystalline solids where molecules of water form cages that trap or surround the methane molecules. The International Union of Pure and Applied Chemistry site, http://www.chem.qmw.ac.uk/iupac/gtpoc/I.... , defines inclusion compounds or inclusion complexes of this type in the following manner: a complex in which one component (the host) forms a cavity or, in the case of a crystal, a crystal lattice containing spaces in the shape of long tunnels or channels in which molecular entities of a second chemical species (the guest) are located. There is no covalent bonding between guest and host, the attraction being generally due to van der Waals forces. If the spaces in the host lattice are enclosed on all sides so that the guest species is "trapped" as in a cage, such compounds are known as "clathrates" or "cage" compounds". What do they look like? A model of a clathrate hydrate «KLATH rayt HY drayt» or a "cage" can be found on the web page http://kristall.unimki.gwdg.de/homep4.htm . Gas hydrates form at moderate pressures (water depths of greater than 300 meters) and low temperatures but above the freezing point of water. More detailed information regarding the structure of hydrates and conditions under which the form can be found in the section, Chemical structure of hydrates, http://www.hydrate.org/about/chemistry.c... . Here, the three known structures of hydrates, types I, II, and H are defined. The structures differ in the number of water and gas molecules. It is believed that other structures may exist. For another point of view, the same information is given on the web site AQUAlibrium , http://www.telusplanet.net/public/jcarro... . This web site has many links and references for further study. Now that we know a bit about hydrates, why is there such a great interest in them? The web site, Ice that burns http://www.sciencenews.org/sn_arc98/11_1... , states that methane hydrate has gone from being considered a nuisance that clogs natural gas fuel lines to possibly being the fuel that powers the 21st century. Just exactly how much methane is contained in hydrates? A lot. This article asserts that the USGS (United States Geological Survey) estimates that approximately 200 trillion cubic feet of natural gas, enough to supply all the nation's energy needs for more than 2,000 years at current rates of use, is hidden below US waters. Methane hydrate programs, http://www.fe.doe.gov/oil_gas/methanehyd... , maintains that worldwide the natural gas contained in methane hydrates might approach 400 million trillion cubic feet. (Take a look at http://www.sciam.com/explorations/1999/1... , to see the distribution of hydrates). Known natural gas reserves are estimated to be in the neighbourhood of 5,000 trillion cubic feet. So there is enormous potential here. But tapping this resource may prove difficult. Both "Ice that burns" and The Mother Lode of Natural Gas , http://www.sciencenews.org/sn_arch/11_9_... , discuss why recovering methane from these deposit may prove difficult or impossible.
Go To Page:
1
2
The copyright of the article Methane Hydrate in Science Websites is owned by . Permission to republish Methane Hydrate in print or online must be granted by the author in writing.
|
