Alcohol, Chemistry and You
Sources and Uses of Ethyl Alcohol

Dr. Bill Boggan

Merlexi Craft: See http://merlexi.com
Ethyl alcohol is derived from two main processes, hydration of ethylene and fermentation of sugars. Hydration of ethylene is the primary method for the industrial production of ethyl alcohol, while fermentation is the primary method for production of beverage alcohol.

Industrial Production: Traditionally, industrial ethanol is manufactured via the acid catalyzed hydration of ethylene. One synthetic route of alcohol by hydration of ethene involves the use of concentrated sulfuric acid (H2SO4). Unfortunately the use of sulfuric acid complicates the process due to concerns about safety, corrosion, and the environment. Current technology allows alcohol to be produced by utilization of zeolites or silica aerogels impregnated with phosphoric or tungstic acid. The distinct advantages of this process are that the reaction can be a one stage process, the catalyst is regenerated, and concerns about safety, corrosion, and the environment are diminished. The reaction with phosphoric acid is as follows: This method has been chosen due to the relative low cost of the ethylene.


H2C = CH2 +

H2PO3
|
O
|
substrate

+H2O -->

HOCH2CH3 +

H2 PO3
|
O
|
substrate

Of the alcohols produced, ethanol is particularly useful in industrial applications because of its relatively high affinity for both water and organic compounds. The composition of other alcohols limit their flexibility as compared to ethanol. For examples, methanol with one carbon (CH3OH) has reduced solubility in hydrocarbons, while increasing the chain length such as in pentanol with 5 carbon units, reduces its solubility in water. Thus, varying the chain length of the alcohol modifies its solubility in different compounds making it more or less useful dependent on the situation.

One problem with the industrial production and utilization of ethanol is that ethanol is the alcohol found in beverages. Thus, industrial alcohol could be the source of large amounts of beverage alcohol. But it has been the practice to tax and control alcohol for beverages and industrial ethanol could be the source for a large amount of illegal alcohol.

In order to reduce the need for strict control and heavy taxation on industrially produced ethanol, the alcohol is denatured. Denaturing is a process of adding other compounds to the ethanol to render it unfit for consumption. Denaturants are selected to give the ethanol a disagreeable taste or odor and in some cases a distinctive color. In some cases the substances added are toxic and produce gastric disturbances upon ingestion and/or other unpleasant symptoms. A large number of different "denaturants" are utilized dependent upon the use for which the ethanol is intended. These denaturants include methyl isobutyl ketone, pyronate, kerosene, acetone, turpentine, amyl alcohol, methyl alcohol, and various butyl alcohols. In some cases more than one denaturant is utilized.

Industrially produced ethanol has many uses including use in solvent based paints, pharmaceuticals, perfumes, cleaning products for home and car, lacquers, and inks.

Further ethanol and other alcohols have been added to gasoline to produce alcohol-containing fuels. Since ethanol contains only one partially oxidized carbon atom, it is flammable and can be used as a fuel. The usual ratio of ethanol to gasoline is ninety parts gasoline to 10 parts ethanol while that for methanol is 97 parts gasoline to 3 parts methanol. Some cars have been designed to run on pure methanol. Gasohol has higher antiknock properties (higher octane) than gasoline, burns more slowly, coolly, and completely. However, it is more expensive and energy intensive to produce and may produce environmental hazards to the individual and to the atmosphere.

Fermentation and Industrial and Beverage Production: All beverage alcohol and much of that used in industry is formed through fermentation of a variety of products including grain such as corn, potato mashes, fruit juices, and beet and cane sugar molasses. (In earlier years, until about 1947, the largest proportion of the production of industrial alcohol was from fermentation, but as was described above the hydration of ethene now provides the greatest source of industrial alcohol). Fermentation can be defined as an enzymatically anaerobic controlled transformation of an organic compound. With respect to alcohol, we are referring to the conversion of sugars to ethanol by microscopic yeasts in the absence of oxygen. The equation for the fermentation of glucose is:

C6H1206 -->
in the presence of yeast
2CH3CH2OH + 2CO2

The figure uses a symbolic notation familiar in biochemistry. It shows the stepwise transformation of glucose to ethanol through intermediates, pyruvate and acetaldehyde.

The initial fermentation mixture contains approximately 3 to 5% ethanol such as in beer and up to 12 to 15% ethanol as in wine and sherry. Higher concentrations of ethanol cannot be achieved by fermentation, because the yeast becomes inactivated. In this case distillation is required to generate higher alcohol concentrations.

Distillation is a process that uses differences in boiling points to separate compounds. In the case of alcohol and particularly ethanol, knowledge that the boiling point of pure water is 100C, while that of ethanol is 78.3C allows the separation of the ethanol from the water by adjusting the distillation temperature to a point higher than that for ethanol, but lower than that for water. Thus, the concentration of ethanol can be enhanced by removing it as a distallate from the ethanol-water solution. Spirits such as gin, scotch, bourbon, and vodka, as well as liqueurs, cordials, and bitters are examples of beverages made from distillation. The distillation procedure also allows for the concentration of components of the beverage which provide some distinctive flavor.

This schematic of laboratory distillation shows a solution heated to force the lowest boiling material into the vapor phase. The vapor passes over the bulb of a thermometer at which point vapor temperature is determined. The vapor condenses to a liquid in the horizontal condenser that is cooled with a flow of cold water. The distillate is collected in a receiver. As the lower boiling point fractions are removed, the temperature of the distillate vapor rises. The operator changes the receiver at selected intervals to isolate distillate of ever increasing boiling point.

Pure ethanol (200proof) cannot be obtained via conventional distillation of a water-ethanol mixture because a constant boiling mixture forms consisting of 95% ethanol-5% water (190 proof). Such a mixture is referred to as an azeotrope (azeotropic = a liquid mixture that is characterized by a constant concentration and constant minimum or maximum boiling point which is lower or higher than any of the components). Further concentration of the ethanol can be achieved by shifting the azeotropic point via vacuum distillation or addition of another substance to the mixture. Often times the compound added is highly toxic such as benzene, therefore absolute alcohol must never be consumed.

The amount of ethyl alcohol in any one beverage varies. Thus, there are differences in the amount of alcohol between beer, wine, champagne and distilled spirits. The amount of alcohol is given as a percentage and also in "proof". The proof of an alcohol beverage is equal to twice the percentage of ethyl alcohol contained therein. Thus, 100 proof ethanol is 50% and 50 proof ethanol is 25%, etc.

ALCOHOL CONTENT IN VARIOUS BEVERAGES

BEVERAGE PERCENT ALCOHOL PROOF
BEER 4 – 6 8 – 12
WINE 7 – 15 14 - 30
CHAMPAGNE 8 – 14 16 – 28
DISTILLED SPIRITS 40 – 95 80 - 190

On the basis of this information you can see that drinking equivalent amounts of beer, wine, champagne, or distilled spirits will provide greatly varying amounts of alcohol to the drinker.

So how much of each would one drink to take in equivalent amounts of alcohol? The answer depends upon the exact alcohol content of each beverage, but on the average 12 ounces of beer is equivalent to 5 ounces of wine which is equivalent to 1.5 ounces of distilled spirits.


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©2003 Kennesaw State University
Principal Investigator Laurence Peterson
Project Director Matthew Hermes