Catalysts and petrol components

• Shorter, branched alkane with a high octane number is formed
• An alkene is formed
• A zeolite catalyst is used

• Alkanes are converted to cycloalkanes and hydrogen
• Cycloalkanes are converted to arenes and hydrogen
• In terms of octane numbers, arenes > cycloalkanes > alkanes
• A platinum catalyst is used

• Product is shorter and more branched than the reactant
• The longest carbon chain becomes shorter, so the octane number increases
• The zeolite isn't a catalyst; it is a sieve to separate the branched and unbranched isomers
• A platinum catalyst is used

How they work:

1. Reactants are adsorbed onto the surface of the catalyst (or bond to the surface).

2. Bonds between the molecules weaken and are broken.

3. New bonds and compounds are formed.

4. The products diffuse away.