What is ethanol?
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a powerful psychoactive drug, best known as the type of alcohol found in alcoholic beverages and in modern thermometers It is also used as a fuel for cars. Ethanol is one of the oldest recreational drugs. In common usage, it is often referred to as alcohol or spirits. Ethanol is avolatile, colorless liquid that has a strong characteristic odor. It burns with a smokeless blue flame that is not always visible in normal light.
How is ethanol made?
There are two ways one is by using plant material and the other is with using ethene which is obtaining from oil.
Ethanol by fermentationEthanol fermentation is a biological process where sugars like glucose, fructose and sucrose get broken down into ethanol using yeast in the absence of air thus this happens:
enzymes
C6H12O6 → 2C2H5OH + 2CO2 + Energy
glucose in yeast ethanol carbon dioxide
Because it is in the absence of oxygen it is classified as anaerobic respiration.
Any substance that has sugar, starch or cellulose can be fermented. (Starch and cellulose break down into glucose.) So ethanol can be made from things like grass, corn, potatoes, wood or corn.
One experiment that can be done to produce ethanol is this.
1. grind the corn, treat it with enzymes to break its starch down into glucose and then add yeast.
2. Leave the material to ferment for 20 to 60 hours.
3. The fermented liquid contains a mixture of substances. Separate the ethanol from it by fractional distillation.
Ethanol from ethene
Ethanol can be made by hydration of ethene.
The ethene is obtained first by cracking long-chain alkanes from oil.
The hydration is exothermic and is reversible. High pressure and low temperature would give the best yield. But in practice it is carried out at 570 degrees Celsius to give a decent rate of reaction.
Difference in the two methodsEthanol by fermentation
The advantages:
It is a renewable like sugarcane or corn.
It is a good way to use organic waste material
Disadvantages:
Need a lot of material to make even a single litre of ethanol.
Fractional distillation uses a lot of energy and money.
Fermentation is slow and tanks must shut down and restart between batches.
When ethanol reaches a certain concentration the yeast stops working.
This limits the amount of ethanol you can get per batch.
Ethanol from ethene
Advantages:
The reaction is fast.
The plant runs continuously. No time is wasted in shutting down and restarting.
It gives pure ethanol.
Disadvantages:
Ethene is made from oil a non-renewable rescource.
Energy is needed to make steam and get the right temperature and pressure for the reaction.
Under the reaction conditions a lot of the ethene remains unreacted. You have to keep recycling it.
Which method is more commonly used?
In countries where oil is cheap they would probably use ethene.
Countries where oil is expensive like the USA fermentation is more commonly used.
In countries where oil is cheap they would probably use ethene.
Countries where oil is expensive like the USA fermentation is more commonly used.
Most Common uses
Ethanol is now commonly used as a fuel for cars as it is more environmentally safe source of fuel, the government takes many measures to ensure people use ethanol as fuel like reducing taxes on it or making flexible-fuel cars that run on ethanol and petrol or the mixture of the two.
Ethanol is also used as a alcoholic drink. It is always made by fermenting for example, Grapes fermented for wine or barley fermented for beer. After it is fermented it is filtered and gotten ready to drink. The mixture of things in the liquid gives it its taste and smell.
http://www.youtube.com/watch?v=IRdOc7Mel28 Video of ethanol
Bibliography Wikipedia,
http://scifun.chem.wisc.edu/CHEMWEEK/PDF/Ethanol.pdf,
http://www.chemguide.co.uk/physical/equilibria/ethanol.html
