3. Industrial Cracking

Question 1

What is crude oil?

Answer 1

A mixture of hydrocarbons containing alkanes cycloalkanes and arenes

Question 2

Which hydrocarbon fractions are in high demand?

Answer 2

Small hydrocarbon fractions are in high demand compared to larger ones though some of the excess heavier fractions are broken down into smaller more useful compounds including alkanes and alkanes with lower MR. This is cracking.

Question 3

What does cracking do?

Answer 3

Large less useful hydrocarbon molecules found in crude oil are broken down into smaller more useful molecules

Question 4

How are these large hydrocarbon molecules cracked?

Answer 4

The large hydrocarbon molecules are fed into a steel chain,amber and heated to a high temperature and then passed over an aluminium oxide catalyst -the chamber doesn’t contain any oxygen to prevent combustion of the hydrocarbon to form water and carbon dioxide

Question 5

What is formed when a large hydrocarbon is cracked?

Answer 5

Smaller alkane and one or more alkane molecules are formed

Question 6

What are low molecular mass alkanes formed to do?

Answer 6

The low molecular mass alkanes formed make good fuels and are in high demand

Question 7

What are the two types of cracking?

Answer 7

Thermal: requires high temperatures up to 1000 degrees
required high pressure up to 70atm
produces alkanes and lots of alkenes

Catalytic: uses a lowere temperature around 450° slight pressure in the presence of a zeolite catalyst produces mainly aromatic hydrocarbons