DF5 : Catalysis and Cracking Flashcards
Are the products of cracking predictable?
No, they are normally random, with the same molecule giving different cracking products
Without a catalyst, what would the cracking process need?
It would require extremely high temperatures and pressures and would take far longer, which would be more expensive
What, in short terms, occurs in the catalytic cracking process?
A hydrocarbon vapour is passed over a heated solid catalyst
What temperature does catalytic cracking take place at?
450 - 500 degrees
Define “catalyst”
A substance that speeds up a chemical reaction but can be recovered chemically
Define “catalysis”
The process of speeding up a chemical reaction using a catalyst
Do catalysts undergo any permanent chemical change during a reaction?
No
Do catalysts change physically?
Yes, they crumble/become roughened
What does catalysts changing physically suggest?
That they take part somewhat in the reaction, although they can be regenerated
How much of a catalyst is usually required?
Only small amounts
What do catalysts affect in the reaction?
Its rate, not the amount of product formed
Do catalysts appear as reactants in the overall equation?
No
Define “homogeneous catalysis”
Catalysis involving a reactant and catalyst in the same physical state
Give one example of homogeneous catalysis
Enzyme catalysed reactions in cells take part in an aqueous solution
Define “heterogeneous catalysis”
Catalysis where the catalysts and products are in different physical states
