Information AboutEthane |
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Ethane is a Chemical Compound with Chemical Formula C2H6. It is the only two-carbon Alkane , that is, an Aliphatic Hydrocarbon . At Standard Temperature And Pressure , ethane is a colourless, odourless Gas . Ethane is isolated on an industrial scale from Natural Gas , and as a byproduct of Petroleum Refining . Its chief use is as Petrochemical Feedstock for Ethylene production. HISTORY Ethane was first prepared synthetically in 1834 by Michael Faraday , by the Electrolysis of a potassium acetate solution, but at the time, he mistook the hydrocarbon product of this reaction for Methane , and did not investigate it further. During the period 1847–1849, in an effort to vindicate the Radical Theory of Organic Chemistry , Hermann Kolbe and Edward Frankland produced ethane by the reductions of Propionitrile (ethyl cyanide) and ethyl iodide with Potassium metal, and, as did Faraday, by the electrolysis of aqueous acetates. They, however, mistook the product of these reactions for Methyl radical, rather than the dimer of methyl, ethane. This error was corrected in 1864 by Carl Schorlemmer , who showed that the product of all these reactions was in fact ethane. Its name was made from the name of Ether , which at first meant Diethyl Ether . CHEMISTRY In the laboratory, ethane may be conveniently prepared by Kolbe Electrolysis . In this technique, an aqueous solution of an Acetate salt is Electrolysed . At the Anode , acetate is oxidized to produce Carbon Dioxide and Methyl radicals, and the highly reactive methyl radicals combine to produce ethane: : CH3COO− → CH3• + CO2 + E− : CH3• + •CH3 → C2H6 Another method, the oxidation of Acetic Anhydride by Peroxide s, is conceptually similar. The chemistry of ethane also involves chiefly Free Radical Reaction s. Ethane can react with the Halogen s, especially Chlorine and Bromine , by Free Radical Halogenation . This reaction proceeds through the propagation of the Ethyl radical: : C2H5• + Cl2 → C2H5Cl + Cl• : Cl• + C2H6 → C2H5• + HCl Because halogenated ethanes can undergo further free radical halogenation, this process results in a mixture of several halogenated products. In the chemical industry, more selective chemical reactions are used for the production of any particular two-carbon halocarbon. Combustion The complete Combustion of ethane releases 1561 kJ/mol, or 51.9 kJ/g, of heat, and produces Carbon Dioxide and Water according to the Chemical Equation : C2H6 + 3½ O2 → 2 CO2 + 3 H2O + 1561 kJ/mol Combustion occurs by a complex series of free-radical reactions. Computer Simulation s of the Chemical Kinetics of ethane combustion have included hundreds of reactions. An important series of reaction in ethane combustion is the combination of an ethyl radical with Oxygen , and the subsequent breakup of the resulting Peroxide into ethoxy and hydroxyl radicals. : C2H5• + O2 → C2H5OO• : C2H5OO• + HR → C2H5OOH + •R : C2H5OOH → C2H5O• + •OH The principal carbon-containing products of incomplete ethane combustion are single-carbon compounds such as Carbon Monoxide and Formaldehyde . One important route by which the carbon-carbon bond in ethane is broken to yield these single-carbon products is the decomposition of the ethoxy radical into a Methyl radical and formaldehyde, which can in turn undergo further oxidation. : C2H5O• → CH3• + CH2O Some minor products in the incomplete combustion of ethane include Acetaldehyde , Methane , Methanol , and Ethanol . At higher temperatures, especially in the range 600–900 °C, Ethylene is a significant product. It arises via reactions like : C2H5• + O2 → C2H4 + •OOH Similar reactions (although with species other than oxygen as the hydrogen abstractor) are involved in the production of ethylene from ethane in Steam Cracking . PRODUCTION After Methane , ethane is the second-largest component of Natural Gas . Natural gas from different gas fields varies in ethane content from less than 1% to over 6% by volume. Prior to the 1960s, ethane was typically not separated from the methane component of natural gas, but simply burnt along with the methane as a fuel. Today, however, ethane is an important Petrochemical feedstock, and it is separated from the other components of natural gas in most well-developed gas fields. Ethane can also be separated from Petroleum Gas , a mixture of gaseous hydrocarbons that arises as a byproduct of Petroleum Refining . Ethane is most efficiently separated from methane by liquefying it at cryogenic temperatures. Various refrigeration strategies exist: the most economical process presently in wide use employs turboexpansion, and can recover over 90% of the ethane in natural gas. In this process, chilled gas expands through a Turbine ; as it expands, its temperature drops to about -100 °C. At this low temperature, gaseous methane can be separated from the liquefied ethane and heavier hydrocarbons by Distillation . Further distillation then separates ethane from the Propane and heavier hydrocarbons. USES The chief use of ethane is in the chemical industry, in the production of Ethylene by Steam Cracking . When diluted with steam and briefly heated to very high temperatures (900 °C or more), heavy hydrocarbons break down into lighter hydrocarbons, and Saturated Hydrocarbon s become Unsaturated . Ethane is favored for ethylene production because the steam cracking of ethane is fairly selective for ethylene, while the steam cracking of heavier hydrocarbons yields a product mixture poorer in ethylene, and richer in heavier Olefin s such as Propylene and Butadiene , and in Aromatic Hydrocarbon s. Experimentally, ethane is under investigation as a feedstock for other commodity chemicals. Oxidative chlorination of ethane has long appeared to be a potentially more economical route to Vinyl Chloride than ethylene chlorination. Many processes for carrying out this reaction have been Patent ed, but poor selectivity for vinyl chloride and corrosive reaction conditions (specifically, a Hydrochloric Acid -containing reaction mixture at temperatures greater than 500 °C) have discouraged the commercialization of most of them. Presently, INEOS operates a 1000 t/a ethane-to-vinyl chloride pilot plant at Wilhemshaven in Germany . Similarly, the Saudi Arabia n firm SABIC has announced construction of a 30,000 t/a plant to produce Acetic Acid by ethane oxidation at Yanbu . This economic viability of this process may rely on the low cost of ethane near Saudi old fields, and it may not be competitive with Methanol Carbonylation elsewhere in the world. Ethane can be used as a refrigerant in cryogenic refrigeration systems. On a much smaller scale, in scientific research, liquid ethane is used to Vitrify water-rich samples for Electron Microscopy . A thin film of water, quickly immersed in liquid ethane at -150 °C or colder, freezes too quickly for water to crystallize. This rapid freezing does not disrupt the structure of Soft Objects present in the liquid state, as the formation of Ice crystals can do. HEALTH AND SAFETY At room temperature, ethane is a flammable gas. When mixed with air at 3.0% – 12.5% by volume, it forms an Explosive mixture. Some additional precautions are necessary where ethane is stored as a cryogenic liquid. Direct contact with liquid ethane can result in severe Frostbite . In addition, the vapors evaporating from liquid ethane are, until they warm to room temperature, heavier than air and can creep along the ground or gather in low places, and if they encounter an ignition source, can flash back to the body of ethane from which they evaporated. Containers recently emptied of ethane may contain insufficient Oxygen to support life. Beyond this Asphyxiation hazard, ethane poses no known acute or chronic toxicological risk. It is not known or suspected to be a Carcinogen . EXTRATERRESTRIAL ETHANE 's surface, taken from an altitude of 16 km by the Huygens Probe . The dark features appear to be drainage channels, but the probe found no evidence for liquids presently on the surface of Titan.]] Ethane has been detected as a trace component in the atmospheres of all four photons of shorter Wavelength s than 160 Nm can photo-dissociate the methane molecule into a Methyl radical and a Hydrogen atom. When two methyl radicals recombine, the result is ethane: : CH4 → CH3• + •H : CH3• + •CH3 → C2H6 In the case of Titan, it was once widely hypothesized that ethane produced in this fashion rained back onto the moon's surface, and over time had accumulated into hydrocarbon seas or oceans covering much of the moon's surface. Infrared telescopic observations cast significant doubt on this hypothesis, and the Huygens Probe , which landed on Titan in 2005, failed to observe any surface liquids, although it did photograph features that could be presently dry drainage channels. In 1996, ethane was detected in Comet Hyakutake , and it has since been detected in some other Comets . The existence of ethane in these distant solar system bodies may implicate ethane as a primordial component of the Solar Nebula from which the sun and planets are believed to have formed. REFERENCES
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