Give the industrial methods of preparation of ethanol .

Explanation

Industrial method of preparation of ethanol . In industry ethanol can be prepared by the following methods .
(i) From ethene . Ethene is converted into ethanol by direct addition of sulphuric acid followed by hydrolysis :
`CH_(2)=CH_(2)+H_(2)SO_(4)overset(350K)toCH_(3)CH_(2)HSO_(4)overset(H_(2)o//Delta)tounderset("Ethanol")(CH_(3)CH_(2)OH)+H_(2)SO_(4)`
(ii) From molasses . Molasses is the mother liquor left after the crystallosation of cane sugar from concentrated juice . It contains `60%` fermentable sugars , mainly sucrose and glucose .Molasses is covnerted to ethanol by the process fo fermentation with the help of yeast .The enzymes invertase and zymase present in the yeast convert sugar into ethyl alcohol as given below :
`underset("Sugar")(C_(12)H_(22)O_(11))+H_(2)Ooverset("Invertase")tounderset("Glucose")(C_(6)H_(12)O_(6))+underset("Fruclose")(C_(6)H_(12)O_(6))`
(iii) From starch , Ethanol can also be prepared from starch Starch is conversion into maltose with the enzyme diastase .
`underset("Starch")(2(C_(6)H_(10)O_(5))_(n))+nH_(2)Ooverset("diastase")tounderset("Maltose")(nC_(12)H_(22)O_(11))`
Yeast is added to the maltose solution .It gives the enzymes maltase and enzyone Maltase converts the maltose into glucose which is converted into ethanol by zymase .
`underset("Maltose")(C_(12)H_(22)O_(11))+H_(2)Ooverset("Maltase")tounderset("Glucose")(C_(6)H_(12)O)`
`underset("Glucose")(C_(6)H_(12)O_(6))overset("Zymase")tounderset("Ethanol")(2CH_(3)CH_(2)OH)+2CO_(2)`