Ethanol Fuel

ethanol

ethanol (ĕth´ənōl´) or ethyl alcohol, CH3CH2OH, a colorless liquid with characteristic odor and taste; commonly called grain alcohol or simply alcohol.

Properties

Ethanol is a monohydric primary alcohol. It melts at -117.3°C and boils at 78.5°C. It is miscible (i.e., mixes without separation) with water in all proportions and is separated from water only with difficulty; ethanol that is completely free of water is called absolute ethanol. Ethanol forms a constant-boiling mixture, or azeotrope, with water that contains 95% ethanol and 5% water and that boils at 78.15°C; since the boiling point of this binary azeotrope is below that of pure ethanol, absolute ethanol cannot be obtained by simple distillation. However, if benzene is added to 95% ethanol, a ternary azeotrope of benzene, ethanol, and water, with boiling point 64.9°C, can form; since the proportion of water to ethanol in this azeotrope is greater than that in 95% ethanol, the water can be removed from 95% ethanol by adding benzene and distilling off this azeotrope. Because small amounts of benzene may remain, absolute ethanol prepared by this process is poisonous.

Ethanol burns in air with a blue flame, forming carbon dioxide and water. It reacts with active metals to form the metal ethoxide and hydrogen, e.g., with sodium it forms sodium ethoxide. It reacts with certain acids to form esters, e.g., with acetic acid it forms ethyl acetate. It can be oxidized to form acetic acid and acetaldehyde. It can be dehydrated to form diethyl ether or, at higher temperatures, ethylene.

Preparation

Ethanol is the alcohol of beer, wines, and liquors. It can be prepared by the fermentation of sugar (e.g., from molasses), which requires an enzyme catalyst that is present in yeast; or it can be prepared by the fermentation of starch (e.g., from corn, rice, rye, or potatoes), which requires, in addition to the yeast enzyme, an enzyme present in an extract of malt. The concentration of ethanol obtained by fermentation is limited to about 10% (20 proof) since at higher concentrations ethanol inhibits the catalytic effect of the yeast enzyme. (The proof concentration of an alcoholic beverage is numerically double the percentage concentration.) For nonbeverage uses ethanol is more commonly prepared by passing ethylene gas at high pressure into concentrated sulfuric or phosphoric acid to form the corresponding ester; the acid-ester mixture is diluted with water and heated, forming ethanol by hydrolysis, and the alcohol is then removed from the mixture by distillation, usually with steam.

Uses

Ethanol is used extensively as a solvent in the manufacture of varnishes and perfumes; as a preservative for biological specimens; in the preparation of essences and flavorings; in many medicines and drugs; as a disinfectant and in tinctures (e.g., tincture of iodine); and as a fuel and gasoline additive (see gasohol). Many U.S. automobiles manufactured since 1998 have been equipped to enable them to run on either gasoline or E85, a mixture of 85% ethanol and 15% gasoline. E85, however, is not yet widely available. Denatured, or industrial, alcohol is ethanol to which poisonous or nauseating substances have been added to prevent its use as a beverage; a beverage tax is not charged on such alcohol, so its cost is quite low. Medically, ethanol is a soporific, i.e., sleep-producing; although it is less toxic than the other alcohols, death usually occurs if the concentration of ethanol in the bloodstream exceeds about 5%. Behavioral changes, impairment of vision, or unconsciousness occur at lower concentrations. See alcoholism.

The Columbia Encyclopedia, 6th ed. Copyright© 2013, The Columbia University Press.

Selected full-text books and articles on this topic

Corn Ethanol: Setting Straight a Misguided Attempt to Free the United States from Foreign Oil
Kurz, Natalie Jean.
Houston Journal of International Law, Vol. 31, No. 2, Spring 2009
Economic Parameters for Corn Ethanol and Biodiesel Production
Eidman, Vernon R.
Journal of Agricultural and Applied Economics, Vol. 39, No. 2, August 2007
Ethanol's Hidden Gasoline Tax; Mandatory Biofuels Will Increase Fuel and Repair Costs
.
The Washington Times (Washington, DC), May 8, 2012
The Dismal State of Biofuels Policy
Ronge, C. Ford; Johnson, Robbin S.
Issues in Science and Technology, Vol. 27, No. 1, Fall 2010
Impact of the Ethanol Boom on Livestock and Dairy Industries: What Are They Going to Eat?
Anderson, David; Anderson, John D.; Sawyer, Jason.
Journal of Agricultural and Applied Economics, Vol. 40, No. 2, August 2008
Agriculture as Energy? the Wisdom of Biofuels
Ferris, John.
Harvard International Review, Vol. 31, No. 2, Summer 2009
The Ethanol Answer to Carbon Emissions: When the United States Gets Serious about the Threat of Global Climate Change, It Should Turn to Ethanol to Power Cars
Lave, Lester B.; Griffin, W. Michael; Maclean, Heather.
Issues in Science and Technology, Vol. 18, No. 2, Winter 2001
The Food versus Fuel Debate: Implications for Consumers
Harrison, R. Wes.
Journal of Agricultural and Applied Economics, Vol. 41, No. 2, August 2009
Corn Ethanol as Energy: The Case against US Production Subsidies
Pimentel, David.
Harvard International Review, Vol. 31, No. 2, Summer 2009
Conditions Necessary for Private Investment in the Ethanol Industry
Kenkel, Philip; Holcomb, Rodney B.
Journal of Agricultural and Applied Economics, Vol. 41, No. 2, August 2009
Sustainable Mobility: Renewable Energies for Powering Fuel Cell Vehicles
Raphael Edinger; Sanjay Kaul.
Praeger, 2003
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