Organic chemistry

Fossil fuels

Catherine Mortimer-Hawkins, IEST

The fossil fuels

• Coal, oil, and gas are fossil fuels.• Remains of plants and animals that lived

million of years ago.• They are all from organic compounds – C.• Give plenty of heat when burned – fuel!• Ex. methane + oxygen carbondioxide + water + energy

(CH4 + 2O2 CO2 + H2O + energy)

Coal

• Dead vegetation collects on the bottom of a swamp.• Decay stops – microbes need oxygen –oxygen

depleted.• Vegetation buried under debris.• Thousands of years.. Sediment piles up. Peat!• Peat gets buried further down, more pressure, more

temp! COAL!• The more pressure, the more temp the harder

coal!

Coal

Dead vegetation in swamp

DEBRIS

SEA

PEATCOAL

Oil & gas

• Formed from the soft remains of sea plants and animals that form on the sea floor.

• Similar stages as in the coal process.• Oil – less dense, migrates up through rock into

oil trap. Ocean

gasImpermeable rock

Oil

Problems!!!

• Contains SULPHIDES – when burning ACID RAIN

• When burning – upsets the natural balanse of CO2 – GLOBAL WARMING

Fractional destillation• Crude oil pumped in at

base.• Compounds boil.• Smallest compounds boil

first – rise to the top.• Other compounds rise

part of the way.• Heaviest stay at the

bottom.• All depending on different

boiling points.• The larger molecules –

less flammable, less runny.

Further pocessing!

• Clean impurities – sulphur compounds.• Some fractions devided into smaller groups – methane,

ethane, prophane…

• Cracking: turns longer molecules into smaller ex. have alot of naphtha but less gasoline, break

naphtha into smaller molecules! it always procuces ethene and propene - plastics!