Cracking
The Crude Oil Problem
Amounts of each fraction you get depend on the proportions of various hydrocarbons in the original crude oil. Far more petrol is needed, than something like bitumen. In other words, fractional distillation of crude oil produces more long-chain hydrocarbons than can be used directly, and fewer short-chain hydrocarbons than required.
The solution? Cracking! Cracking is a useful process in which large hydrocarbon molecules are broken into smaller ones. Most of the hydrocarbons found in crude oil are long-chain alkanes. Cracking can convert these into alkenes and shorter alkanes. It is an example of thermal decomposition.
How it Works
| What is Needed:
ü Alumina/Silica as catalyst ü 600-7000C
|
The fraction is heated to give a gas and is passed over a catalyst of silica or alumina with a temperature of 600-700oC.
Long alkane -> alkene + alkane
- Sometimes you may get more than one type of alkene/alkane.
- Make sure the numbers of carbon and hydrogen are balanced.
In an equation, this would read: hexane -> butane + ethene C6H14 -> C4H10 + C2H4