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Wednesday, September 4, 2013



ETHANOL FROM CELLULOSE Presentation Transcript:
1. Ethanol is a colorless, volatile and flammable liquid belonging to a group of organic chemicals known as alcohols.
It has a density of 0.789g/cm3, a boiling point of 78˚C and its structural formula is written as:

 2. Other names used to refer to ethanol include:
Absolute alcohol
Ethyl alcohol
Drinking alcohol
Grain alcohol
Ethyl hydrate
Ethyl hydroxide

3. Uses of Ethanol
As Fuel – to power motor vehicles or as an additive to gasoline to improve its octane rating.
Alcoholic beverages  – ethanol is the major constituent (with psychoactive effects) in alcoholic drinks.
As an antiseptic at concentrations of 62%v/v.
As a solvent – its found in several products such as markers, tinters and paint as it is one of the best solvents.
As a raw material in the production of plastics, acetic acid, perfumes, plasticizers, among others.

4. Methods of Production
Ethanol is usually produced by two methods:
Hydration of Ethylene
C2H4 + H2O → CH3CH2OH
2. Fermentation of sugar-containing plant parts like corn, sugar beets, sugar cane, e.t.c
C6H12O6 → 2CH3CH2OH + 2CO2

5. Cellulose
It is an organic polymer made up of linear chains of thousands of linked beta(1-4) D-glucose units. It is a major constituent of plant cell walls and forms approx. 45-60% of woody plants.
Its formula is written as:

6. Cellulosic Ethanol
Ethanol produced from cellulosic materials is referred to as cellulosic ethanol.
As explained earlier, cellulose is made up of linear chains of linked beta D-glucose molecules. Glucose molecules can be obtained from cellulose chains by hydrolysis. The glucose obtained can then fermented to form ethanol.

7. Examples of Cellulosic Materials include:
Switch Grass
Wood chips
Corn stover
Wheat straw

8. But Why Cellulosic Ethanol?
Most countries that produce ethanol in large quantities, such as Brazil, rely on food crops such as corn and sugar cane. This inevitably brings competition with food supply.
Cellulose presents an alternative to this since it is mainly contained in the non-food plant parts, that mostly go unutilised, e.g agricultural and forest residue.
Lignin, a waste product of this process, has high calorific value and can be used to fire boilers.

9. Methods of Producing Cellulosic Ethanol
There exist two methods of producing ethanol from cellulosic materials:

10. 1. Cellulolysis
This is also known as the biological approach and it involves five or six steps depending on the level of purity required.
The steps are…

11. i. Pretreatment
The purpose of pretreatment is to free cellulose from lignin( one of the plant polymers which acts as a seal ), exposing it for hydrolysis.
The methods used include:
Physical pretreatment (size reduction) e.g milling
Chemical pretreatment e.g acid hydrolysis, organosolv, ammonia fiber explosion.

12. ii. Cellulose Hydrolysis
This involves breakdown of the long chains of beta D-glucose to free glucose molecules. This process avails the sugar contained in cellulose for fermentation.
Its usually achieved by either of the following methods:
Enzymatic hydrolysis – cellulose enzymes are used to biologically break down cellulose to glucose.
Chemical hydrolysis – an acid, usually sulphuric acid, is used.

13. iii. Separation
The sugar formed from the hydrolysis process is separated from residual material such as lignin.

14. iv. Fermentation
Microbes are used to ferment the glucose formed into ethanol.
Cellulosic materials usually contain hemicellulose polymer. When this is hydrolysed, a 5-carbon sugar called xylose, is usually formed.
For this reason, microorganisms used for this process should be capable of fermenting xylose.

15. Commonly used microbes include:
Saccharomyces cerevisiae
Zymomonas mobilis
Escherichia coli

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