Crude oils and fuels

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Crude oils and fuels
Crude oil and fuels
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Overview crude oil

• Crude oil is derived from an ancient biomass
  found in rocks.
• Many useful materials can be produced from crude
  oil.
• Crude oil can be fractionally distilled. Some of
  the fractions can be used as fuels.

What useful materials can be made from crude oil?
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Overview biofuels

• Biofuels are produced from plant material.
• There are advantages and disadvantages to their
  use as fuels.
• Fuels can come from renewable or non-renewable
  resources.

What are the advantages and disadvantages of
biofuels?
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Crude oil
Crude oil is a mixture of a large number of
compounds. A mixture consists of two or more
elements or compounds not chemically combined
together. The chemical properties of each
substance in the mixture are unchanged. It is
possible to separate the substances in a mixture
by physical methods, including distillation.
Why does crude oil have so many different
compounds in it?
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Hydrocarbons 1
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, which have the
general formula CnH2n2.
What would a model of ethane (two carbons) look
like?
A molecular model of methane and its structural
formula
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Hydrocarbons 2
The many hydrocarbons in crude oil may be
separated into fractions by evaporating the oil
and allowing it to condense at a number of
different temperatures. Each fraction contains
molecules with a similar number of carbon atoms.
This process is called fractional distillation.
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Fractional distillation
Explain how the fractionating column works.
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Properties 1
Some properties of hydrocarbons depend on the
size of their molecules. Look at the table below
and on the next slide. What patterns do you
notice?
Fraction Carbon atoms in the molecule Description Boiling point (?C) Flammability Uses
Petroleum gas 14 Colourless gas Less than 40 Explodes if mixed with air and lit Used as a fuel in the refinery Bottled and sold as LPG
Naphtha 510 Yellowish liquid, flows easily 25175 Evaporates easily, vapour mixed with air is explosive Petrol Used for making other chemicals
Kerosene 1014 Yellowish liquid, flows like water 150260 Burns when heated Aircraft fuel
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Properties 2
Fraction Carbon atoms in molecule Description Boiling point (?C) Flammability Uses
Light gas oil 1420 Yellow liquid, thicker than water 235360 Only burns when soaked onto a wick or other material Diesel fuel
Heavy gas oil 2050 Yellow brown liquid 330380 Only burns when soaked onto a wick very smoky Used in the catalytic cracker
Lubricants (car engine oils) 5060 Thick brown syrup-like liquid 340575 Only burns when hot and soaked onto a wick Grease for lubrication Catalytic cracker
Fuel oil 6080 Thick brown sticky liquid Above 490 Only burns when hot and soaked onto a wick Fuel oil for power stations and ships
Bitumen More than 80 Black semi-solid Above 580 Only burns if very hot Road and roof surfaces
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Hydrocarbon fuels 1
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) may
also be released.
What problems do carbon dioxide, sulfur dioxide
and particulates cause? (Answers on the next
slide.)
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Hydrocarbon fuels 2
The combustion of hydrocarbon fuels releases
heat. During combustion, the carbon and hydrogen
in the fuels are oxidised.

• Sulfur dioxide causes acid rain.
• Carbon dioxide causes global warming.
• Solid particles cause global dimming.

How can these effects be reduced? (Answers on the
next slide.)
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Hydrocarbon fuels 3
Sulfur can be removed from fuels before they are
burned, for example in vehicles. Sulfur dioxide
can be removed from the waste gases after
combustion, for example in power stations using
scrubbers. Catalytic converters in the exhausts
of vehicles reduce the release of nitrogen
oxides.
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Biofuels
Biofuels, including biodiesel and ethanol, are
produced from plant material, e.g palm oil. There
are economic, ethical and environmental issues
surrounding their use.
What are the issues with biofuels?
Shariff CheLah/Fotolia
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