1. Oil refining and its Products

2. Petrol and Crude Oil
Crude oil is separated by fractional distillation
works because the molecules have different boiling/condensation points
many of these hydrocarbons are alkanes, and are sorted into fractions
each fraction has a range of boiling points in the distillation
narrow boiling ranges of limited carbon number (eg light gasoline is C5 to C7 boiling point 25C -75C)
Gasoline and gas oil fractions are sources of petrol components
Naptha used for high grade petrol and chemical feedstocks

3. Fractionation of Crude Oil Fractions and their uses
Refinery Gas (LPG)
Light Gasoline (Petrol)
Naphtha (Petrol)
Kerosene (Jet Fuel)
Gas Oil (Diesel Fuel)
Residue Fractions (Bitumen)

4. Natural Gas
Natural gas is an extremely fuel both for domestic and industrial use.
It is a mixture consisting mostly of methane, CH4, (at least 85%), ethane, C2H6, (up to 10%) and small amounts of propane, C3H8, and butane, C4H10.

5. Liquid Petroleum Gas (LPG)
The gases in the refinery gas fraction are bottled and sold for domestic use.
Propane and butane from this fraction can be readily liquefied under pressure and are referred to as liquid petroleum gas (LPG).

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

7. Petrol Composition Complex mixture of compounds Mainly Hydrocarbons
Branched – chain alkanes
Aromatic Compounds

8. Petrol in the Internal Combustion Engine
Vaporised
Mixed with air
Compressed
Ignited and burned
Gases produced expand
Kinetic Energy

9. Premature Ignition Problem: Auto-ignition (i.e. knocking or pinking)
Effects: a) Loss of power
b) Engine damage
Prevention: a) Additives
b) Use suitable mixtures of high-octane compounds

10. Octane Rating Measure of tendency to resist auto-ignite or
Measure of tendency to cause knocking
Low octane rating makes auto-ignition more likely

11. Octane Rating 2,2,4-tri-methylpentane Octane Number =100 Heptane

12. Additives Lead compounds e.g. tetra ethyl lead Prevents reactions
Harmful environmental effects
Phased out in 2000
Oxygenates e.g. ROR orROR1 MTBE
Raise octane number
Cause less pollution

13. Mixture of compounds with high octane numbers
Molecular features:
Degree of branching – the more the better
Chain length – the shorter the better
Presence of rings – highly desirable

14. High octane numbers can be obtained from low by:
Isomerisation
Dehydrocyclisation
Catalytic cracking
All three methods involve the use of catalysts

15. Isomerisation Take a straight chain alkane e.g. pentane (O.N.62)
C ─ C ─ C ─ C ─ C
Heat in the presence of a catalyst
Chain breaks
Bits rejoin to form a branched compound e.g.2-methylbutane (O.N.93)
C ─ C ─ C ─ C │ C

16. Dehydrocyclisation Take a straight chain alkane e.g. hexane (O.N. 25)
Catalyst causes change to a cycloalkane (O.N. 83)
C6H14 → (CH2)6 + H2
Catalyst causes the cycloalkane to change to an aromatic compound e.g. benzene (O.N. >100)
(CH2)6 → 3H C6H6
Benzene

17. Catalytic Cracking Heavy oil e.g. kerosine or diesel
High temperature and catalyst
Molecule breaks into several smaller molecules
Unsaturated products are used as feedstock for the polymer industry
Saturated products are usually high octane branched chain alkanes suitable for making petrol

18. CH3 ─ (CH2)10 ─ CH3 ↓ CH3 CH3 │ │ CH3 ─ CH ─ CH2 ─ CH ─ CH3 + CH3 │
│ │
CH3 ─ CH ─ CH2 ─ CH ─ CH3 +
CH3 │
CH2 = C ─ CH2 ─ CH3