Cracking Crude Oil Flashcards
What happens after distillation of crude oil?
You have still got both short and long hydrocarbons just not all mixed together.
What does cracking mean?
Splitting up long-chain hydrocarbons by passing vapour over a hot catalyst.
What do long-chain hydrocarbons form?
Thick gloopy liquids like tar which aren’t that useful.
What happens to the long-chain hydrocarbons?
They are turned into smaller ones by a process called cracking.
Some of the products of cracking are useful as what?
Fuels.
eg petrol for cars and paraffin for jet fuel.
What does cracking also produce?
Substances like ethene which are needed for making plastics.
EG when diesel goes through the process of cracking what does it turn into?
Petrol.
Paraffin.
Ethene for plastics.
What type of reaction is cracking?
Thermal decomposition reaction.
What does thermal decomposition do?
Break down molecules by heating them.
Describe the process of cracking.
The first step is to heat the long-chain hydrocarbons to vaporise it - turn into gas.
Then the vapour is passed over a powered catalyst at a temperature of about 400C - 700C.
Aluminium oxide is the catalyst used.
The long chain molecules spilt apart or ‘crack’ on the surface of the specks of catalyst.
What are most of the products of cracking?
Alkanes and unsaturated hydrocarbons called alkenes.
What is the catalyst used in cracking?
Aluminium oxide.
What is the alternative way of cracking long-chain hydrocarbons?
To mix the vapour with steam at a very high temperature.
EG What does kerosene turn into?
Kerosene has 10 C atoms - too much of this in crude oil.
It turns into.
Octane with 8 C atoms - useful for petrol.
Ethene with 2 C atoms - making plastics.
