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ckejyetf9k · Posted: Wed 17:13, 04 Sep 2013 Post subject: barbour uk Ethyl Alcohol Or Wine

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Submitted : 2013-05-15 00:00:00Word Count : 858Popularity: Not RatedTags: Ethyl alcohol or wine , Synthetic method , Ethyl hydrogen sulphate
Ethyl alcohol is by far the most important member of the monohydric alcohol series and it is often simply known as 'alcohol'. It is also known as spirit of wine or grain alcohol.

Preparation

In fact ethyl alcohol is not prepared in the laboratory. Due to its large demand, it is generally prepared on a commercial scale. Two important method for its manufacture are : 1. Synthetic method 2. Fermentation process.

1. Synthetic method :

(i) From ethylene: Large amount of ethylene [link widoczny dla zalogowanych] is obtained by thermal cracking of petroleum and natural gas. This ethylene is absorbed in hot 85% concentrated H2S04 at high pressure and at 85-100°C to produce ethyl hydrogen sulphate. The reaction mixture is then diluted with water and boiled. The ethyl alcohol produced by hydrolysis of ethyl hydrogen sulphate, is obtained by fractional distillation. The remaining sulphuric acid is concentrated and reused. The yield is about 90%.

?? ?? 85- 100°C CH3CH2Q O hp [link widoczny dla zalogowanych]

CH2 = CH2 S high pressure ' /( -* CH2CH2OH + H2SG4

HO U 6 F HO X> Ethanol

Ethylene Sulphuric acid

r Ethyl hydrogen sulphate

(ii) In another method, a mixture of pure ethylene and steam is passed over phosphoric acid catalyst, absorbed over a support (diatomaceous earth), at 100 atm pressure and heated at 300°C, when alcohol is formed by hydration of ethylene. It is extracted from the unreacted gas by wa ter and is recovered by fractional distillation :

H3PO4

ch2 = ch2 + h2o 300oC/100atm> ch3ch2oh

Ethylene " Ethanol

2. Fermentation process:

Fermentation : A complex chemical process of [link widoczny dla zalogowanych] decomposition of large organic compounds into much simpler molecules by enzymes (acting as catalysts), obtained from lower unicellular plants and animals such as yeast, moulds, fungi and bacteria, is called Fermentation. Yeast, moulds, etc., are a kind of micro-organism and different kinds of micro-organism produce different enzymes. A particular enzyme can catalyse only a particular chemical reaction. Thus, to produce a particular compound, only a specific kind of micro-organism can be used. Since micro-organisms are used to carry out these chemical reactions, fermentation is also called biochemical reaction.

Manufacture : Ethyl alcohol is made from cheap raw materials : (i) Starchy materials such as rice, maize, potato, grain, barley, etc. (ii) Molasses, a by-product of sugar industry, (i) From starch by fermentation: Among the starchy material, the production of potato is comparatively high and its price is less in comparison to others. Thus, potato has been selected as the industrial raw material for fermentation. The conversion of starch to ethanol takes place in following steps :

Step I: Starch to maltose : Potatoes are cut into small pieces and are heated'with steam at [link widoczny dla zalogowanych] 140° - 150°C under pressure when starch-grains [(C6H10O5)n] come out from [link widoczny dla zalogowanych] the cells ,of potatoes and on cooling form a paste. The paste is then mixed with a little germinating barley or malt. The mixture is kept at 50°C for about an hour, when the enzyme diastase

present in malt, acting as a catalyst and hydrolysis starch into the sugar, maltose, C12H22Ou :

[link widoczny dla zalogowanych] 2(C6H10O5)n + nH2O diaStaSe ) nC12H22On Starch Maltose

Step II: Maltose --[Glucose] -——> Ethanol: The liquid is then cooled to about 30°C,

mixed with yeast and the mixture is kept for 2-3 days. The enzyme maltase present in the yeast converts (hydrolysis) maltose to glucose :

Ypacf wr

C12H22On + H20 Y2ltzse ' 2C6H12°6 Maltose D-Glucose

Another enzyme zymase, present in yeast cells, converts glucose to ethanol and evolve carbon dioxide:

C6Hl2°6 ^Sf^2CH3CH2OH + 2C02 D-Glucose zymase

The [link widoczny dla zalogowanych] produced C02, a by-product, is utilised elsewhere according to the need such as to produce aerated drinks, dry ice, etc.

During the above fermentation process, due to liberation of [link widoczny dla zalogowanych] C02, the liquid mixture begins to froth, giving the appearance of boiling (the word fermentation is coined from the Latin fervere means 'to boil').

The ethanol obtained by the fermentation process is in the form of very dilute aqueous solution (8-10%). This solution is called fermented liquor, marketed under the name Beer.

(ii) From molasses by fermentation :'Molasses is the mother liquor left after crystallisation [link widoczny dla zalogowanych] of cane sugar from the concentrated cane juice. It is a dark coloured viscous liquid which still contains 30% sucrose and 32% invert sugar, i.e., a mixture of glucose and fructose. Operation : The molasses [link widoczny dla zalogowanych] is diluted with water so far as to provide optimum concentration required [link widoczny dla zalogowanych] for fermentation. The diluted solution contain about 10-15% sugar, is fermented at ~30°C in large tanks by addition of yeast in slightly acidic [link widoczny dla zalogowanych] medium. [link widoczny dla zalogowanych] Small amount of salt such as (NH4)2S04 or (NH4)3P04 are added for nutrition of yeast. Mild acid condition is maintained by adding dil. H2S04, which favours the growth of the yeast. The fermentation [link widoczny dla zalogowanych] is an exothermic reaction. The yeast has a dual function upon the cane sugar — the enzyme invertase first converts cane sugar into glucose and fructose, which are then fermented into ethanol under the influence of zymase, essentially as described above :

c12h22ou+h2o (i^"rsttase)- c6h12o6 + c6h12o6.

Sucrose D - Glucose D - Fructose

I_^_:_l

yeast (zymase)

c2h5oh + co2

The fermented liquid contain 6-12% ethanol. The process takes about 2 days.
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Ethyl Alcohol Or Wine
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