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What is a catalyst?

A catalyst increases the rate of a reaction by providing an alternative reaction pathway with a lower activation energy.

What is cracking?

the breakdown of large hydrocarbons into smaller, more useful alkanes and alkenes

How and why is a catalyst used in the cracking processes?

Without a catalyst process would require extremely high temps and pressures making it expensive

Cracking can take place at a much lower temperature (around 450•c) and pressure, over a heated solid catalyst it lowers the activation energy

Heterogenous

A catalyst that is in a different phase from the reactants or products

How does a heterogenous catalyst work?

Reactant molecules arrive at the surface of the catalyst and bond- called adsorption

Bonds in the reactants weakened and break to form radicals (atoms/molecules with unpaired electrons)

Radicals react with eachother to make new molecules

New molecular are then detached from surface of catalyst called desorption

What is catalyst poisoning?

The poison absorbs better to the surface of the catalyst than the reactant

Causes less reaction efficiency and yield

2 examples of catalysts poisoning?

Carbon monoxide poisons the solid iron catalysts used in the haber process

Lead poisons catalyst in catalytic converters- problem when lead was added to petrol OK now as there’s unleaded petrol

What is catalysis?

Acceleration of a chemical reaction by a catalyst