INDUSTRIAL PREPARATION OF ETHANOL
 
Method # 1
By the fermentation of molasses
 WHAT IS MOLASSES
On industrial scale, ethanol can be prepared by the fermentation of molasses. Molasses is the mother liquor left after the crystallization of sugarcane juice. It is a dark coloured viscous liquid. Molasses contains about 60% fermentable sugar.
METHOD OF PREPARATION
 
Following steps are involved in the preparation of ethyl alcohol :
 
DILUTION OF MOLASSES
 
Molasses is first diluted with water in 1:5 (molasses : water) ratio by volume.
 
ADDITION OF AMMONIUM SULPHATE
 
If nitrogen content of molasses is small, it is now fortified with ammonium sulphate to provide adequate supply of nitrogen to yeast.
ADDITION OF SULPHURIC ACID
 
Fortified solution of molasses is then acidifies with small quantity of sulphuric acid. Addition of acid favours the growth of yeast but unfavours the growth of useless bacteria.
FERMENTATION
 
The resulting solution is received in a large tank and yeast is added to it at 30O C and kept for 2 to 3 days. During this period, enzymes sucrase and zymase which are present in yeast, convert sugar into ethyl alcohol.
C12H22O11 + H2O C6H12O6 + C6H12O6

C6H12O6 C2H5OH + 2CO2
FRACTIONAL DISTILLATION
 
Alcohol obtained by the fermentation is called WASH, which is about 15% to 18% pure. By using fractional distillation technique, it is converted into 92% pure alcohol which is known as rectified spirit or commercial alcohol.
 
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