Industrial Cracking

Question 1

Why is Cracking done

Answer 1

Meet oil demands
Shorter chains are more valuable
Alkanes very unreactive so must be cracked

Question 2

What temperature and pressure is Thermal Cracking done at

Answer 2

700-1200K, 7000KPa

Question 3

What temperature and pressure is catalytic cracking done at

Answer 3

720K, Low pressure but more than atomospheric

Question 4

What is used in catalytic cracking

Answer 4

Zeolites, AlO and SiO2
Zeolite in honeycomb for large SA + Acidic

Question 5

What is the test for a C-C double bond

Answer 5

Add Excess reactant and shake , will decolourise bromine solution

Question 6

What happens in thermal cracking

Answer 6

C-C bonds break as homolyctic fission
2 shorter chains produced
Each carbon has unpaired electron, free radicals produced
1 chain bonds to H atom to form alkane
1 Chain forms double bond to form alkene, insufficient hydrogen

Question 7

What happens in catalytic cracking

Answer 7

Zeolite catalyst used at lower temp + pressure
Produces mostly branched alkanes, cycloalkanes and aromatic compounds
Products mostly gaseous
Chain length < C5
Products separated via fractional distillation