Ethyl alcohol is used in large quantities as an antiseptic, as fuel and as a solvent. It is one of the best and most important solvents in the chemical and pharmaceutical industries. It can be obtained by the fermentation of food sources such as wheat, rye, barley, maize, triticale (a high resistant to fungal and viral diseases and at low temperatures hybrid of rye and wheat), potatoes, through saccharification and subsequent fermentation contained therein starch. In addition, it can be obtained by hydrolysis of wood waste from the wood industry and subsequent fermentation of the resulting glucose:
Hydrolysis of starch and cellulose is step process where the intermediate products are obtained as dextrins, maltose, etc. This explains the need for addition of the enzyme glucoamylase in the fermentation mixture which is capable of degrading the dextrins to fermentable sugars. During the fermentation process a large amount of heat is separated and it has to be efficiently compensated (by appropriate cooling) in order to maintain the viability of the yeast. The fermentation process may have duration between 24 and 80 hours depending on the specific conditions and the way of processing. The disadvantage is the fact that both ethanol and other higher alcohols (fraction known among the population as light liquor) are produced due to the decarboxylation and release of ammonia from proteins contained in the used natural products. Further, from thus obtained mixture of alcohols, the ethanol (which is represented about 12-18%) can be recovered by distillation and rectification process, which follow after the fermentation cycle.
At the beginning and the middle of the last century a number of chemical methods for the industrial production of ethanol have been developed. The most common are:
- ethyne (acetylene) hydration and subsequent reduction of the resulting acetaldehyde
- hydration of ethene (ethylene), produced by coke oven gas, cracking and pyrolysis processes in the oil in a medium of sulfuric acid.
Ethanol is widespread in nature in the form of ethyl esters and may be prepared therefrom by hydrolysis reaction.
