1. 21(a) Oil Refining and its Products

2. Crude Oil Distillation columns Oil rig
Photo - Chris Grossman
Oil rig
Distillation columns

3. Fractional Distillation of Crude Oil

4. Fractional Distillation of Crude Oil
Small molecules
Low boiling point
Large molecules
High boiling point

5. Fractional Distillation of Crude Oil
Crude oil is separated by fractional distillation
Molecules have different boiling/condensation points
Many of these hydrocarbons are alkanes, and are sorted into fractions
They are separated as groups of compounds with similar boiling points
The temperature of the fractionating column is maintained at a high level at the bottom and decreases up the column
Substances with higher boiling points condense in the lower part of the fractionating column and those with lower boiling points condense at the higher part of the column.

6. The Fractions Fraction Length of C Chain Uses Refinery Gas C1 – C4
Bottled and sold for domestic use
(cooking etc)
LPG: Liquified Petroleum Gas
Petrol (light gasoline)
C5 – C10
Motor fuel
Naptha
C7 – C10
Petrochemical industry: production of plastics, medicines, synthetic fibres, detergents
Kerosene (paraffin)
C10 – C14
Domestic heating oil
Aircraft fuel
Diesel oil (gas oil)
C14 – C19
Fuel for buses, trucks, trains and cars
Lubricating oil
C14 – C35
Lubricant to reduce wear and tear
Waxes and polishes
Fuel oil
C30 – C40
Fuel for ships and power stations
Bitumen
> C35
Tar for roads and roofing

7. Mercaptans
Very smelly, organic sulfur compounds that are added to natural gas and LPG so that leaks can be detected

8. Combustion Engine Air drawn in Petrol injected
→ air-fuel mixture created
Spark ignites petrol-air
Atomised diesel spontaneously combusts in high temp

9. Auto-ignition / Knocking
The premature ignition of the petrol-air mixture before normal ignition of the mixture by a spark
Effects: a) Loss of power
b) Engine damage
Prevention: a) Additives
b) Use suitable mixtures of high-octane compounds

10. Octane Number A measure of the tendency of a fuel to resist knocking
* A low octane number makes auto-ignition (knocking) more likely → the lower the octane number, the less efficient the fuel

11. Octane Number 2,2,4-trimethylpentane Octane # = 100 Heptane
→These are reference hydrocarbons

12. Factors that Affect Octane Number
Length of Chain
Degree of branching
Straight chain or cyclic structure

13. Factors that Affect Octane Number
Length of Chain
The shorter the chain, the higher the octane number
Butane
Octane # = 94
Heptane
Octane # = 0

14. Factors that Affect Octane Number
2. Degree of Branching The more branched the chain, the higher the octane number
3-methylhexane
Octane # = 65
2,3-dimethylpentane
Octane # = 91

15. Factors that Affect Octane Number
3. Straight Chain or Cyclic Structure Cyclic compounds have a higher octane number than straight chain compounds
Hexane
Octane # = 25
Cyclohexane
Octane # = 83

16. Methods to Increase Octane Number
Isomerisation
Catalytic Cracking
Dehydrocyclisation
Adding Oxygenates

17. Isomerisation Changing straight chain alkanes into their isomers
Heated in the presence of a catalyst
Chain breaks
Bits rejoin to form a branched compound
E.g:
Pentane
Octane # = 62
2-methylbutane
Octane # = 93

18. Catalytic Cracking
The breaking down of long-chain hydrocarbon molecules into short chain-molecules using heat and catalysts
E.g:
Cracking
C12H26
2,4-dimethylpentane
2-methylbut-1-ene

19. Catalytic Cracking
Unsaturated products (alkenes) are used as feedstock for the polymer industry
Saturated products (alkanes)are usually high octane branched chain alkanes suitable for making petrol

20. Dehydrocyclisation Using catalysts
To form ring compounds from straight-chain alkanes
E.g:
Hexane
Octane # = 25
Cyclohexane
Octane # = 83

21. Methyl tertiary-butyl ether
Adding Oxygenates
Need to know all 3!
Oxygen containing compounds: *Oxygenates also give rise to very little pollution
MTBE
Methyl tertiary-butyl ether
Methanol
Ethanol

22. Adding Oxygenates Lead compounds e.g. tetra ethyl lead
Prevents reactions
Harmful environmental effects
Phased out in 2000

23. Manufacture of Hydrogen
Steam Reforming of Natural Gas
CH4 + H2O = 3 H CO
In presence of a suitable catalyst

24. Manufacture of Hydrogen
Electrolysis of Water
using dilute H2SO4
forms at cathode [negative electrode]
Overall
H2O = H /2 O2
Too expensive in most parts of world

25. Uses of Hydrogen
Fuel - about 10% of worlds production of hydrogen is used as fuel
Environmentally friendly
Water is the only product of combustion
H /2 O2 = H2O
It is explosive with air
Difficulties with storage and transport

26. Uses of Hydrogen Haber Process for producing ammonia N2 + 3 H2 = 2 NH3
Hydrogenating vegetable oils

27. Fuel Cell