C.2 Fossil Fuels Flashcards

1
Q

How are fossil fuels produced?

A

Reduction of biological molecules within dead organisms.
Carbon, hydrogen, nitrogen, sulphur and oxygen.
Result is a carbon rich fuel.

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2
Q

What is crude oil?

A

A complex mixture of different hydrocarbons

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3
Q

What happens during crude oil refining?

A

Mixture undergoes fractional distillation, physical process, separates on their boiling point.

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4
Q

What happens during fractional distillation?

A

1 - crude oil heated until it boils
2 - vapour passes into the fractionating column
3 - temperature is higher at bottom of column than top
4 - different fractions condense and drawn off at different heights
5 - highest boiling points condense towards bottom of tower
6 - smaller hydrocarbons travel up the column until they condense and are drawn off

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5
Q

What is the refinery gases fraction used for?

A

Fuel for cooking and heating, bottled gas, fuel in the refinery.

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6
Q

What is the gasoline fraction used for?

A

Fuel for cars.

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7
Q

What is the naphtha fraction used for?

A

Feedstock for petrochemical industry, converted by catalytic reforming into gasoline, used as a solvent.

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8
Q

What is the kerosene (paraffin) fraction used for?

A

Jet fuel, household heaters and lamps, cracked to produce more gasoline.

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9
Q

What is the diesel oil (gas oil) fraction used for?

A

Diesel fuel for cars, lorries etc. cracked to produce more gasoline.

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10
Q

What is the fuel oil fraction used for?

A

Fuel for ships and industry, fuel for home central heating systems.

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11
Q

What is the lubricating oil fraction used for?

A

Lubricant in engines and machinery, may be cracked.

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12
Q

What is the wax fraction used for?

A

Candles, petroleum jelly, waxed paper and cardboard in the food industry.

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13
Q

What is the bitumen/asphalt fraction used for?

A

Tarmac for roads and waterproofing roofs.

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14
Q

What is volatility?

A

How readily a substance evaporates.

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15
Q

How does the carbon chain length change over the fractions?

A

It increases as you move down the fraction from refinery gas to asphalt.

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16
Q

How does volatility change over the fractions?

A

It decreases as chain length increases, (from refinery gases to asphalt).

17
Q

How does mean boiling temperature change over the fractions?

A

It increases from refinery gas down the fractions to asphalt

18
Q

What is auto ignition?

A

Occurs when fuel in the cylinder of an engine burns instantly (explodes), leads to knocking which can cause excessive engine wear and damage.

19
Q

What is an octane number?

A

An experimentally derived value provides a measure of the tendency of a fuel to auto ignite. HIGHER octane number LOWER tendency of fuel to auto ignite.

20
Q

What are octane numbers dependent on and why?

A

Carbon chain length - LONGER the chain the LOWER the octane number
Chain branching - branching INCREASES the octane number for the same number of carbon atoms
Cyclisation - cyclisation INCREASES the octane number for the same number of carbon atoms
Unsaturation - alkenes tend to have a HIGHER octane number than alkane equivalents.

21
Q

How can octane numbers be increased?

A

By cracking or catalytic reforming.

22
Q

What is cracking?

A

Long chain alkanes are passed over an aluminosilicate catalyst heated to 500 degrees Celsius under pressure. Resulting in a shorter chain alkane and one or more alkene molecules. Alkane molecules may also cyclise or become branched during the process.

23
Q

What is catalytic reforming?

A

Hydrocarbons are passed over a platinum catalyst at 500 degrees celsius. The molecules become branched, cyclised or aromatised.

24
Q

What is coal gasification?

A

Solid coal converted into a gaseous fuel (syngas a mixture of CO and hydrogen). Heating coal to temperature above 1000 degrees Celsius in the presence of oxygen and steam.
The main reaction occurring is:
C(s) + H20(g) —-> CO(g) + H2(g)
Syngas can be converted to methane by heating it with additional hydrogen:
CO(g) + 3H2(g) —-> CH4(g) + H20(g)

25
Q

What is coal liquefaction?

A

Coal converted to liquid hydrocarbons. One method involves mixing coal with solvent and hydrogen and heating to about 400 degrees celsius at high pressure and in the presence of a catalyst such as red mud (from bauxite purification).

26
Q

How else can coal liquefaction occur?

A

Produce liquid hydrocarbon from syngas using Fischer Tropsch process. At temperature of 300 degrees Celsius higher pressure and presence of ruthenium catalyst, the CO reactions with H2 to form liquid alkanes.

27
Q

What is a carbon footprint?

A

Total amount of greenhouse gas produced during the course of a human activity. Expressed in equivalent tonnes of carbon dioxide (CO2e).