Crude Oil

BTEOTSSSBAT:

know the origin of crude oil understand the components and properties of

hydrocarbons,

Key wordsCrude oilCompoundMixtureDistillationHydrocarbonsSaturatedAlkanesCovalent bondEvaporatingCondenseFractional distillationFractionating columnParticulatesCombustionSootBiofuels

• Microscopic plants and animals die and fall to the sea bed

• Layers of sand and mud form on top

• Pressure and high temperature cause oil to form

How crude oil was formed

• Oil obtained by drilling

Oil is a fossil fuelOther fossils fuels are:

Coal and Gas

Non-renewable Renewable

Biofuels – ethanol and biodiesel made from plants

Crude oil is a mixture of a very large number of compounds.

These compounds can be separated by distillation.

Heated Crude Oil

350oC

40oC

Liquid petroleum gas

Naphtha

Petrol (gasoline)

Paraffin

Diesel

Fuel oil

Lubricating oil

Bitumen

Fraction Boiling pt.

< 25oC

25 – 60oC

60 – 180oC

180 – 220oC

220 – 250oC

250 – 300oC

300 – 350oC

> 350oC

Average number of C atoms in chain

3

8

10

12

20

40

80

120

The Fractional Distillation of Crude Oil

Very hot crude oil is pumped intothe fractionating column where the hydrocarbons separate out by their boiling points, rising through the column until they get cold enough to condense. The compounds that condense at a particular temperature are called a FRACTION.

Properties of the fractions

Most of the compounds in crude oil consist of molecules made up of hydrogen and carbon atoms only (hydrocarbons). Most of these are saturated hydrocarbons called alkanes.

Write the chemical formula for these alkanes

In general:

CH4 C2H6

C3H8

C4H10

CnH2n+2

Alkane molecules can be represented in the following forms:

Fuels

Most alkanes are used as fuels to produce useful forms of energy.

When completely burned alkanes form carbon dioxide and water.

Equations for combustion

CH4

methane

+ O2

oxygen

CO2

carbon dioxide

+ H2O

water

2 2

C3H8 + O2 CO2 + H2O

C2H4 + O2 CO2 + H2O2 2

5 3 4

3

Most fuels, including coal, contain carbon and/or hydrogen and may also contain some sulfur.

The gases released into the atmosphere when a fuel burns may include:•carbon dioxide •water (vapour)•carbon monoxide •sulfur dioxide and •oxides of nitrogen. Solid particles (particulates - sometimes called soot) may also be released.

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