C1bL5 Making Ethanol

Key Words

Alcohol - a carbon compound that has an -OH group in it.  Usually used to describe ethanol.

Biofuel - fuel made from living things that can power cars.

Catalyst - substance that enables a chemical reaction to happen, but is not used up in the chemical reaction.

Ethanol - a compound consisting of an ethane chain onto which an alcohol group is attached

Ethene - an alkene of two carbon atoms with a double bond between them.

Fermentation - a reaction that breaks sugar into ethanol and carbon dioxide in the absence of oxygen

Flammable - can catch fire readily.

Fractional distillation - process that separates hydrocarbons from the mixture in crude oil.

Pharmaceuticals - chemicals that can be used as medicines.

Renewable - energy sources that capture the energy of the Sun now.

Solvent - substance that dissolves another substance.

Yeast - a micro-organism that ferments sugar to alcohol.

Grade E

Ethanol has a chemical formula C₂H₅OH.  Its structural formula is:

It is one of many alcohols, but it is the alcohol which makes people drunk.  It is highly flammable.

It can be made from crude oil in a two stage process:

1. By cracking hydrocarbons to make ethene;
2. By passing ethene and steam over a catalyst, phosphoric acid.  This makes the second reaction much faster.

Ethanol produced this way is often called industrial alcohol.

Grade C

The ethanol we drink in alcoholic drinks is made by fermentation, where yeast breaks sugar to form ethanol and carbon dioxide.  The yeast stops working at about 20 % ethanol, so the ethanol is concentrated by distillation.  It can be then used as biofuel.

Since the sugars that the yeast ferments are gained from living crops, the process is renewable.  This makes more sense than using non-renewable sources.  However the fermentation process is less efficient.

Grade A

Fermentation is the following reaction, carried out by yeast in the absence of oxygen:

sugar solution  ® ethanol + Carbon dioxide

C₆H₁₂O₆ ® 2C₂H₅OH + 2CO₂

The ethanol is removed by fractional distillation, since it boils at about 70 ^oC compared to 100 ^oC for water.

Water is a solvent that dissolves many chemicals.  It dissolves ethanol.  However ethanol, too, is a solvent, which can dissolve substances that do not dissolve in water.  This is very useful in the manufacture of pharmaceuticals.