Ethyl Alcohol
| Infobox on Ethyl Alcohol | |
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| Example of Ethyl Alcohol |  |
| Facts | |
| Origin | - |
| Stowage factor (in m3/t) | - |
| Humidity / moisture | - |
| Ventilation | - |
| Risk factors | See text |
Ethyl Alcohol
Description
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol. Ethanol is produced both as a petrochemical, through the hydration of ethylene and, via biological processes, by fermenting sugars with yeast. Which process is more economical depends on prevailing prices of petroleum and grain feed stocks.
Ethanol is a clear, colourless liquid that is made up of a group of chemical compounds whose molecules contain a hydroxyl group, -OH, bonded to a carbon atom. Fuel-grade ethanol is blended with a percentage of gasoline, thus forming a “finished” motor oil product.
Ethanol can be produced from any biological feedstock (corn, barley, wheat) that contains substantial amounts of sugar or materials that can be converted into sugar (starch, cellulose). In particular, corn contains starch that can relatively easily be converted into sugar. Many larger ethanol producers use a wet-milling process to make corn, which also yields products such as high-fructose corn sweetener.
The ethanol production process starts by grinding up the feedstock so it is more easily and quickly processed in the following steps. Once ground up, the sugar is either dissolved out of the material or the starch or cellulose is converted into sugar. The sugar is then fed to microbes that use it for food, producing ethanol and carbon dioxide in the process. A final step purifies the ethanol to the desired concentration.
Ethyl alcohol is also known as ethanol, drinking alcohol or grain alcohol. It is the pivotal ingredient in alcoholic drinks. It is an inflammable, colourless slightly toxic compound with a distinct odour. It is also the alcohol that is present in all alcoholic beverages.
Ethanol is also produced for industrial purposes and finds use as a clean burning bio-fuel. Ethyl alcohol is sometimes adulterated with methyl alcohol or methanol. This is a more potent alcohol and is dangerous to consume as it gets broken down in the liver to form toxic compounds like formic acids and formaldehyde - the compounds can destroy the optic nerve leading to blindness. Other dangerous symptoms include - acidosis that may progress to death by respiratory failure.
Ethanol for use as an industrial feedstock or solvent (sometimes referred to as synthetic ethanol) is made from petrochemical feed stocks, primarily by the acid-catalyzed hydration of ethylene, represented by the chemical equation C2H4 + H2O → CH3CH2OH
The catalyst is most commonly phosphoric acid, adsorbed onto a porous support such as silica gel or diatomaceous earth. The reaction is carried out with an excess of high pressure steam at 300°C.
Solvent properties
Ethanol is a versatile solvent, miscible with water and with 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, and with aliphatic chlorides such as trichloroethane and tetrachloroethylene.
Ethanol-water mixtures have less volume than the sum of their individual components at the given fractions. Mixing equal volumes of ethanol and water results in only 1.92 volumes of mixture. Mixing ethanol and water is exothermic, with up to 777 J/mol being released at 298 K.
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 the wine's 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.
Grades of ethanol
Ethanol is available in a range of purities that result from its production or, in the case of denatured alcohol, are introduced intentionally.
Denatured alcohol
Pure ethanol and alcoholic beverages are heavily taxed as a psychoactive drug, but ethanol has many uses that do not involve consumption by humans. To relieve the tax burden on these uses, most jurisdictions waive the tax when an agent has been added to the ethanol to render it unfit to drink. These include bittering agents such as denatonium benzoate and toxins such as methanol, naphtha, and pyridine. Products of this kind are called denatured alcohol.
Absolute alcohol
Absolute or anhydrous alcohol refers to ethanol with a low water content. There are various grades with maximum water contents ranging from 1% to ppm levels. Absolute alcohol is not intended for human consumption. If azeotropic distillation is used to remove water, it will contain trace amounts of the material separation agent (e.g. benzene). Absolute ethanol is used as a solvent for laboratory and industrial applications, where water will react with other chemicals, and as fuel alcohol. Spectroscopic ethanol is an absolute ethanol with a low absorbance in ultraviolet and visible light, fit for use as a solvent in ultraviolet-visible spectroscopy.
Rectified spirits
Rectified spirit, an azeotropic composition of 96% ethanol containing 4% water, is used instead of anhydrous ethanol for various purposes. Wine spirits are about 94% ethanol (188 proof). The impurities are different from those in 95% (190 proof) laboratory ethanol.
Application
Ethanol has widespread use as a solvent of substances intended for human contact or consumption, including scents, flavourings, colourings, and medicines. In chemistry, it is both an essential solvent and a feedstock for the synthesis of other products. It has a long history as a fuel for heat and light, and more recently as a fuel for internal combustion engines.
Ethanol, also known as ethyl alcohol, is a clear colourless liquid with a mild and pleasant odour. It is widely used in various products such as alcoholic beverages, solvents, perfumes and toiletries, disinfectants, polishes, as a fuel additive and in the manufacture of plastics, rubber and drugs. It is also increasingly being used as a biofuel. Alcohol-based hand gels in the form of liquids, foams and gels can contain up to 95% ethanol.
Most people will be exposed to ethanol in the form of alcoholic beverages in which ethanol is found at varying concentrations from 4% to 45%. However exposure to higher concentrations may occur in an occupational setting such as in industry, where 100% ethanol is sometimes used. In such environments safe levels are enforced to protect workers. If exposed to ethanol, the potential
adverse health effects that may occur depend on the way people are exposed and the amount to which they are exposed. Exposure via breathing ethanol vapours can cause irritation of the nose and throat with choking and coughing at higher concentrations.
Drinking ethanol causes a range of symptoms which are dependant on the amount that is consumed. Symptoms range from impaired vision, reaction time and co-ordination to slurred speech,blackouts, nausea and vomiting. Drinking larger amounts may cause convulsions, coma and breathing problems. Skin exposure from spillages of ethanol can cause burning and stinging. Eye exposure
to ethanol can also cause burning and stinging.
The largest single use of ethanol is as a motor fuel and fuel additive. More than any other major country, Brazil relies on ethanol as a motor fuel. Gasoline sold in Brazil contains at least 25% anhydrous ethanol. Hydrous ethanol (about 95% ethanol and 5% water) can be used as fuel in more than 90% of new cars sold in the country. Brazilian ethanol is produced from sugar cane and noted for high carbon sequestration.The US uses Gasohol (max 10% ethanol) and E85 (85% ethanol) ethanol/gasoline mixtures.
Shipment / Storage
An ethanol-water solution that contains 40% ABV (alcohol by volume) will catch fire if heated to about 26 °C and if an ignition source is applied to it. This is called its flash point. The flash point of pure ethanol is 16.60 °C, less than average room temperature.
Boiling Point: The lowest known value is 78.5°C (Ethyl alcohol 200 Proof). Weighted average: 79.58°C
Melting Point: May start to solidify at -114.1°C based on data for: Ethyl alcohol 200 Proof.
Critical Temperature: The lowest known value is 243°C (Ethyl alcohol 200 Proof).
Specific Gravity: Weighted average: 0.8 (Water = 1)
Store in a segregated and approved area. Keep container in a cool, well-ventilated area. Keep container tightly closed and sealed until ready for use. Avoid all possible sources of ignition (spark or flame). Do not store above 23°C.
Bioethanol: See http://www.elobio.eu/fileadmin/elobio/user/docs/DeliverableE_5.1.pdf
Risk factors
For overseas carriage aspects of Chemicals, the readers are recommended to acquire or have access to a good chemical dictionary, and a copy of the International Maritime Dangerous Goods (IMDG) Code, issued by the International Maritime Organisation. Also consult the applicable MSDS sheet.