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Anhydrous Alcohol - Purified Ethanol
Ethanol, also known as ethyl alcohol, drinking alcohol or grain alcohol, is a flammable, colorless,
mildly toxic chemical compound, and is best known as the alcohol found in alcoholic beverages. In common usage, it is often referred to simply as alcohol. It is a straight-chain alcohol and its molecular formula is variously
represented as EtOH, CH3CH2OH, C2H5OH or as its empirical formula C2H6O (which it shares with dimethyl ether).
After the use of fire, fermentation of sugar into ethanol is perhaps the earliest organic reaction known to
humanity, and the intoxicating effects of ethanol consumption have been known since ancient times. In modern times ethanol intended for industrial use has also been produced from byproducts of petroleum refining.
Because of
ethanol's ease of production and because exposure to low amounts does negligible harm, it has widespread use as a solvent for substances intended for human contact or consumption, including scents, flavorings, colorings, and
medicines. In chemistry it is both an essential solvent and a feedstock for the synthesis of other products. Because it burns cleanly, ethanol has a long history as a fuel, including as a fuel for internal combustion engines.
History
Ethanol has been used by humans since prehistory as the intoxicating ingredient in alcoholic beverages. Dried residues on 9000-year-old pottery found in China imply the use of alcoholic beverages even among Neolithic people. Its
isolation as a relatively pure compound was first achieved by Muslim chemists who developed the art of distillation during the Abbasid caliphate, the most notable of whom were Jabir ibn Hayyan (Geber), Al-Kindi (Alkindus) and
al-Razi (Rhazes). The writings attributed to Jabir ibn Hayyan (721-815) mention the flammable vapors of boiled wine. Al-Kindi (801-873) unambiguously described the distillation of wine. Absolute ethanol was obtained in 1796 by
Johann Tobias Lowitz, by filtering distilled ethanol through charcoal.
Antoine Lavoisier described ethanol as a compound of carbon, hydrogen, and oxygen, and in 1808, Nicolas-Théodore de Saussure determined ethanol's
chemical formula. Fifty years later Archibald Scott Couper published a structural formula for ethanol, which places ethanol among the first of chemical compounds to have its chemical structures determined.
Ethanol was first
prepared synthetically in 1826, through the independent efforts of Henry Hennel in Great Britain and S.G. Sérullas in France. Michael Faraday prepared ethanol by the acid-catalyzed hydration of ethylene in 1828, in a process
similar to that used for industrial ethanol synthesis today.
Ethanol served as lamp fuel in the United States as early as 1840, although taxes levied during the Civil War on industrial alcohol rendered the practice
uneconomical. The tax was not repealed until 1906, and from 1908 Ford Model T automobiles could be adapted to run on ethanol. With the advent of Prohibition in 1920 though, sellers of ethanol fuel were accused of being allies of
moonshiners, and ethanol fuel once again faded from the public eye. The recent rise in oil prices has spurred renewed interest.
Political support has also increased recently for more ethanol based products. For example,
Hillary Clinton originally opposed ethanol research efforts, stating in 2002 that "there is no sound public policy reason for mandating the use of ethanol." Now, Senator Clinton, and many other leaders from both the
Republican and Democratic party are supporters of ethanol-based fuel solutions.
Physical properties
Chemical structure of ethanol
The properties of ethanol stem primarily from the presence of its hydroxyl group and the shortness of
its carbon chain. Ethanol's hydroxyl group is able to participate in hydrogen bonding, rendering it more viscous and less volatile than less polar organic compounds of similar molecular weight. Ethanol, like most short-chain
alcohols, is flammable, colorless, has a strong odor, and is volatile.
Ethanol is slightly more refractive than water with a refractive index of 1.36242 (at ¥=589.3 nm and 18.35 °C).
Ethanol is a versatile solvent,
miscible in all proportions with water and many organic solvents, including acetic acid, acetone, benzene, carbon tetrachloride, chloroform, diethyl ether, ethylene glycol, glycerol, nitromethane, pyridine, and toluene. It is also
miscible with light aliphatic hydrocarbons such as pentane and hexane, as well as aliphatic chlorides such as trichloroethane and tetrachloroethylene. Ethanol's miscibility with water is in contrast to longer chain alcohols (five
or more carbons), whose water solubility decreases rapidly as the number of carbons increases.
Hydrogen bonding causes pure ethanol to be hygroscopic to the extent that it readily absorbs water from the air. The polar nature
of the hydroxyl group causes ethanol to dissolve many ionic compounds, notably sodium and potassium hydroxides, magnesium chloride, calcium chloride, ammonium chloride, ammonium bromide, and sodium bromide. Sodium and potassium
chlorides are slightly soluble in ethanol. Because the ethanol molecule also has a nonpolar end, it also dissolves nonpolar substances, including most essential oils, as well as numerous flavoring, coloring, and medicinal agents.
Several unusual phenomena are associated with mixtures of ethanol and water. Ethanol-water mixtures have less volume than their individual components. A mixture of equal volumes ethanol and water has only 95.6% of the
volume of equal parts ethanol and water, unmixed (at 15.56 °C). The addition of even a few percent of ethanol to water sharply reduces the surface tension of water. This property partially explains the tears of wine phenomenon.
When wine is swirled in a glass, ethanol evaporates quickly from the thin film of wine on the wall of the glass. As its ethanol content decreases, its surface tension increases, and the thin film beads up and runs down the glass in
channels rather than as a smooth sheet.
Ethanol and mixtures with water greater than about 50% ethanol are flammable and easily ignited. This principle was used for the alcoholic proof, which initially consisted on adding
gunpowder to a given liquor: if the mixture ignited, it was considered to be "100 proof". Ethanol-water solutions below 50% ethanol by volume may also be flammable if the solution is vaporized by heating (as in some
cooking methods that call for wine to be added to a hot pan, causing it to flash boil into a vapor, which is then ignited to "burn off" excessive alcohol).
Types of ethanol
Denatured alcohol
Pure ethanol and alcoholic beverages are
heavily taxed. Ethanol has many applications that do not involve human consumption. To relieve the tax burden on these applications, most jurisdictions waive the tax when agents have been added to the ethanol to render it unfit for
human consumption. These include bittering agents such as denatonium benzoate, as well as toxins such as methanol, naphtha, and pyridine.
Absolute ethanol
Absolute or anhydrous alcohol generally refers to purified ethanol,
containing no more than one percent water. Absolute alcohol not intended for human consumption often contains trace amounts of toxic benzene (used to remove water by azeotropic distillation).
Pure ethanol is classed as 200 proof in the USA, equivalent to 175 degrees proof in the UK system.
Use
As a fuel
The largest single use of ethanol is as a motor fuel and fuel additive. The largest national fuel ethanol industries exist in Brazil
(gasoline sold in Brazil contains at least 20% ethanol and anhydrous ethanol is also used as fuel).
Henry Ford designed the first mass-produced automobile in the US, the famed Model T Ford to run on pure anhydrous [ethanol]
alcohol -- he said it was "the fuel of the future". Today, however, 100 % pure ethanol is not approved as a motor vehicle fuel, even though compared to gasoline, ethanol cuts poisonous gas emissions [carbon monoxide,
nitrous oxides, sulfur dioxide] and produces fewer greenhouse gases that cause global climate change. Added to gasoline, ethanol also reduces ground-level ozone formation by lowering volatile organic compound and hydrocarbon
emissions, decreasing carcinogenic benzene, and butadiene, emissions, and particulate matter emissions from gasoline combustion. Since 90% of US crude oil reserves have been consumed, the US must import crude oil to meet energy
demand. Substituting ethanol for gasoline would substantially reduces the foreign trade deficit, which is aggravated by crude oil [and gasoline] imports.
Today, almost half of Brazilian cars are able to use 100% ethanol as
fuel, which includes ethanol-only engines and flex-fuel engines. Flex-fuel engines [in Brazil] are able to work with all ethanol, all gasoline, or any mixture of both. In the US flex-fuel vehicles can run on zero% to 85%
ethanol(15% gasoline) since higher ethanol blends are not yet allowed. Brazil supports this population of ethanol-burning automobiles with large national infrastructure that produces ethanol from domestically grown sugar cane.
Sugar cane not only has a greater concentration of sucrose than corn (by about 30%), but is also much easier to extract. The bagasse generated by the process is not wasted, but is utilized in power plants as a surprisingly
efficient fuel to produce electricity.
World production of ethanol in 2006 was 51 billion liters, (13.5 billion gallons), with 69% of the world supply coming from Brazil and the United States.
The United States fuel
ethanol industry is based largely on maize. According to the Renewable Fuels Association, as of October 30, 2007, 131 grain ethanol biorefineries in the United States have the capacity to produce 7.0 billion gallons of ethanol per
year. An additional 72 construction projects underway (in the U.S.) can add 6.4 billion gallons of new capacity in the next 18 months. Over time, it is believed that a material portion of the ~150 billion gallon per year market for
gasoline will begin to be replaced with fuel ethanol.
The Energy Policy Act of 2005 requires that 4 billion gallons of "renewable fuel" be used in 2006 and this requirement will grow to a yearly production of 7.5
billion gallons by 2012.
A Ford Taurus "fueled by clean burning ethanol" owned by New York City.
A Ford Taurus "fueled by clean burning ethanol" owned by New York City.
In the United States, ethanol
is most commonly blended with gasoline as a 10% ethanol blend nicknamed "gasohol". This blend is widely sold throughout the U.S. Midwest, and in cities required by the 1990 Clean Air Act to oxygenate their gasoline during
the winter.
Controversy
As reported in "The Energy Balance of Corn Ethanol: an Update," the energy returned on energy invested (EROEI) for ethanol made from corn in the U.S. is 1.34 (it yields 34%
more energy than it takes to produce it). Input energy includes natural gas based fertilizers, farm equipment, transformation from corn or other materials, and transportation. However, other researchers report that the production
of ethanol consumes more energy than it yields. However, recent research suggests that cellulosic crops such as switchgrass provide a much better net energy production, producing over five times as much energy as the total used to
produce the crop and convert it to fuel. If this research is confirmed, cellulosic crops will probably displace corn as the main fuel crop for producing bioethanol, and existing calculations of potential will need a major revision.
Environmentalists, livestock farmers, and opponents of subsidies say that increased ethanol production won't meet energy goals and may damage the environment as food prices soar. Some of the controversial subsidies in the
past have included more than $10 billion to Archer-Daniels-Midland since 1980. Critics also speculate that as ethanol is more widely used, changing irrigation practices could greatly increase pressure on water resources. In October
2007, 28 environmental groups decried the Renewable Fuels Standard (RFS), a legislative effort intended to increase ethanol production, and said that the measure will "lead to substantial environmental damage and a system of
biofuels production that will not benefit family farmers...will not promote sustainable agriculture and will not mitigate global climate change." Recent articles have also blamed subsidized ethanol production for the nearly
200% increase in milk prices since 2004, although that is disputed by some.
Oil has historically had a much higher EROEI than agriculturally produced ethanol, according to some. However, oil must be refined into gasoline
before it can be used for automobile fuel. Refining, as well as exploration and drilling, consumes energy. The difference between the energy in the fuel (output energy) and the energy needed to produce it (input energy) is often
expressed as a percent of the input energy and called net energy gain (or loss). Several studies released in 2002 estimated that the net energy gain for corn ethanol is between 21 and 34 percent. In comparison, gasoline production
yields a net energy loss of between 19 and 20 percent. The net energy loss for MTBE is about 33 percent. When added to gasoline ethanol can replace MBTE as an anti-knock agent without poisoning drinking water as MBTE does. Further
agricultural practices and ethanol production improvements could lead to an increase in ethanol net energy gain in the future. Consuming known oil reserves is increasing oil exploration and drilling energy consumption which is
reducing oil EROEI (and energy balance) further.
Some say the amount of ethanol needed to run the United States is greater than its own farmland could produce, even if fields now used for food were converted for production
of non-food-grade corn. It has been estimated that "if every bushel of U.S. corn, wheat, rice and soybean were used to produce ethanol, it would only cover about 4% of U.S. energy needs on a net basis." This ignores the
fact that ethanol in the future will be produced from thrown away cellulose in the form of Biomass from forest products, switch grass, waste paper, and other material, technologies that are just getting underway today. The
calculation for how much gasoline can potentially be replaced by corn ethanol [excluding corn stover cellulose] is not that difficult. The US has 2,263 million acres of farmland. The average corn yield is 140 bushels per acre The
ethanol yield from corn kernal distillation alone, excluding corn stover cellulosic ethanol, is 2.5 gallons per bushel. This results in over 792 billion gallons of ethanol (multiplying the 3 items above). Taking into account the
fact that ethanol has approximately 69% of the energy per gallon of gasoline (http://en.wikipedia.org/wiki/Energy_density) this results in the displacement of 549 billion barrels of gasoline, which is much over the 146 billion
gallons per year of gasoline consumed each year in the US. This total does not include cellulosic ethanol.
In the United States, preferential regulatory and tax treatment of ethanol automotive fuels introduces complexities
beyond its energy economics alone. North American automakers have in 2006 and 2007 promoted a blend of 85% ethanol and 15% gasoline, marketed as E85, and their flex-fuel vehicles, e.g. GM's "Live Green, Go Yellow"
campaign. The apparent motivation is the nature of U.S. Corporate Average Fuel Economy (CAFE) standards, which give an effective 54% fuel efficiency bonus to vehicles capable of running on 85% alcohol blends over vehicles not
adapted to run on 85% alcohol blends. In addition to this auto manufacturer-driven impetus for 85% alcohol blends, the United States Environmental Protection Agency had authority to mandate that minimum proportions of oxygenates be
added to automotive gasoline on regional and seasonal bases from 1992 until 2006 in an attempt to reduce air pollution, in particular ground-level ozone and smog. In the United States, incidents of methyl tert(iary)-butyl ether
(MTBE) groundwater contamination have been recorded in the majority of the 50 states, and the State of California's ban on the use of MTBE as a gasoline additive has further driven the more widespread use of ethanol as the most
common fuel oxygenate.
Rocket fuel
Ethanol was commonly used as fuel in early bipropellant rocket vehicles, in conjunction with an oxidizer such as liquid oxygen. The German V-2 rocket of World War II, credited with
beginning the space age, used ethanol, mixed with water to reduce the combustion chamber temperature. The V-2's design team helped develop U.S. rockets following World War II, including the ethanol-fueled Redstone rocket, which
launched the first U.S. satellite. Alcohols fell into general disuse as more efficient rocket fuels were developed.
Alcoholic beverages
Ethanol is the principal psychoactive constituent in alcoholic
beverages, with depressant effects to the central nervous system. It has a complex mode of action and affects multiple systems in the brain, most notably ethanol acts as an agonist to the GABA receptors. Similar psychoactives
include those which also interact with GABA receptors, such as gamma-hydroxybutyric acid.
Alcoholic beverages vary considerably in their ethanol content and in the foodstuffs from which they are produced. Most alcoholic
beverages can be broadly classified as fermented beverages, beverages made by the action of yeast on sugary foodstuffs, or as distilled beverages, beverages whose preparation involves concentrating the ethanol in fermented
beverages by distillation. The ethanol content of a beverage is usually measured in terms of the volume fraction of ethanol in the beverage, expressed either as a percentage or in alcoholic proof units.
Fermented beverages
can be broadly classified by the foodstuff from which they are fermented. Beers are made from cereal grains or other starchy materials, wines and ciders from fruit juices, and meads from honey. Cultures around the world have made
fermented beverages from numerous other foodstuffs, and local and national names for various fermented beverages abound.
Distilled beverages are made by distilling fermented beverages. Broad categories of distilled beverages
include whiskeys, distilled from fermented cereal grains; brandies, distilled from fermented fruit juices, and rum, distilled from fermented molasses or sugarcane juice. Vodka and similar neutral grain spirits can be distilled from
any fermented material (grain or potatoes are most common); these spirits are so thoroughly distilled that no tastes from the particular starting material remain. Numerous other spirits and liqueurs are prepared by infusing flavors
from fruits, herbs, and spices into distilled spirits. A traditional example is gin, which is created by infusing juniper berries into a neutral grain alcohol.
In a few beverages, ethanol is concentrated by means other than
distillation. Applejack is traditionally made by freeze distillation, by which water is frozen out of fermented apple cider, leaving a more ethanol-rich liquid behind. Eisbier (more commonly, eisbock) is also freeze-distilled, with
beer as the base beverage. Fortified wines are prepared by adding brandy or some other distilled spirit to partially-fermented wine. This kills the yeast and conserves some of the sugar in grape juice; such beverages are not only
more ethanol-rich, but are often sweeter than other wines.
Alcoholic beverages are sometimes used in cooking, not only for their inherent flavors, but also because the alcohol dissolves hydrophobic flavor compounds which
water cannot.
Chemical derivatives of ethanol
Ethanol is an important industrial ingredient and has widespread use as a base chemical for other organic compounds. These include ethyl halides, ethyl esters, diethyl ether, acetic
acid, butadiene, and ethyl amines.
Antiseptic use
Ethanol is used in medical wipes and in most common antibacterial hand sanitizer gels at a concentration of about 62% (percentage by weight, not volume) as an antiseptic. Ethanol kills
organisms by denaturing their proteins and dissolving their lipids and is effective against most bacteria and fungi, and many viruses, but is ineffective against bacterial spores.
Antidote
Although ethanol has mild toxic effects at high
doses, it is sometimes used as an antidote for poisoning by other, more toxic alcohols, in particular methanol and ethylene glycol. Ethanol competes with other alcohols for the alcohol dehydrogenase enzyme, preventing metabolism
into toxic aldehyde and carboxylic acid derivatives.
Other uses
* Ethanol is easily miscible in water and is a good solvent. Ethanol is less polar than water and used in perfumes, paints and tinctures.
* Ethanol is also used in design and sketch art markers, such as Copic, and Tria.
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