Alkanes

Thermal cracking

• High temperatures up to 1000 degrees celcius

• High pressures up to 70 atm

• Produces high % of alkenes

• Used to make polymers such as polyethene

Catalytic cracking

• Zeolite catalyst

• Slight pressure

• High temperature 450 degrees celcius

• Produces aromatic hydrocarbons and motor fuels

• Using a catalyst cuts costs, can be done at a low pressure and lower temperature

• Saves time as it speeds up the reaction

Economic reasons for cracking

Longer carbon chains are not very useful, light fractions are in higher demand

Complete combustion of alkanes e.g. methane

CH4 + 2O2 => CO2 + 2H2O

• Alkanes are good fuels as they release a lot of energy when burnt

Incomplete combustion of alkanes e.g. methane

2CH4 + 3O2 => 2CO + 4H2O

Fraction

A mixture of compounds with similar boiling points