Crude OIl

Differences Between shorter chain and longer chain hydrocarbons

Shorter chains are found at the top of the fractionating column as they have lower boiling points than longer chains as less energy is required to break the weaker intermolecular forces.

Longer chains are more viscous than Shorter chains

Shorter chains are more flammable than longer chains

What happens in a fractionating column

Fraction distillation occurs

The crude oil is made up of different hydrocarbons. It is heated until most of the crude oil is turned to gas.

The liquid part is drained off and called bitumen.

There is a temperature gradient in the fractionating column. At the top is coldest and bottom is hottest. The hydrocarbons are drained off by different taps placed at different heights.

At the temperature in the column that is the hydrocarbons boiling point, they turn into a liquid are are subsequently drained out of the column

Shorter chain hydrocarbons are drained higher as the shorter the chain the lower the boiling point, whereas longer chains are drained lower done the column.

Why is cracking needed

There is a higher demand for shorter chain hydrocarbons than longer chain hydrocarbons

What type of reaction is cracking

Thermal decomposition (The breaking down of larger, complex molecules into shorter, more simple molecules)

Conditions for cracking

600-700 degrees Celsius

A catalyst (Silica or Alumina)

Method for Cracking

The Alkane is heated until it is vaporised

It then breaks down when it comes into contact with catalyst producing a mixture of short chain alkanes and alkenes