Question

industrial preparation of ethenol

Answer 1

Method # 1 By the fermentation of starch
WHAT IS STARCH 
Starch is carbohydrate and is an important source of ethanol. Generally potato, rice, maize or barley are used as source of starch. Use of potato for starch is very common.
STEPS OF PREPARATION
EXTRACTION OF STARCH The crushed potato is steamed at 140OC to 150OC under pressure to prepare starch solution known as MASH.
GERMINATION Before hydrolysis, starch is first undergo germination at 10OC to 13OC for few days. This germinated starch is called MALT.
HYDROLYSIS OF STARCH Satrch is hydrolysed to maltose by an enzyme known as diastase.
2(C6H10O5) + nH2O  n(C12H22O11)
Starch Maltose 
FERMENTATION Finally yeast is added to maltose. 
Yeast secrets two enzymes:
1. Maltase: converts maltose into glucose.
2. Zymase: converts glucose into ethanol..
C12H22O11 + H2O  2C6H12O6
C6H12O6  C2H5OH + 2CO2


Method # 2: 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.

Answer 2

Ethanol is produced from biomass mostly via a fermentation process using glucose derived from sugars (sugar cane, sugar beet and molasses), starch (corn, wheat, grains) or cellulose (forest products) as raw materials. ... Synthetic ethanol can also beproduced from non-renewable sources like coal and gas.