1. What is Coal, oil and Gas (Fuse school)

2. CHEMICAL PROPERTIES OF ALKANES
Introduction - fairly unreactive
Combustion - make useful fuels
complete CH4(g) O2(g) ——> CO2(g) H2O(l)
combustion
incomplete CH4(g) ½O2(g) ——> CO(g) H2O(l)
the greater the number of carbon atoms, the more energy produced
BUT the greater the amount of oxygen needed for complete combustion.
Fuse School: Combustion

3. Processes involving combustion give rise to a variety of pollutants...
POLLUTION
Processes involving combustion give rise to a variety of pollutants...
power stations SO2 emissions produce acid rain
internal combustion engines CO, NOx and unburnt hydrocarbons
Removal
SO2 chimney scrubbers react effluent gases with bases (e.g. CaO)
CO and NOx pass exhaust gases through a catalytic converter
Catalytic converters
In the catalytic converter ... CO is converted to CO2
NOx are converted to N2
Unburnt hydrocarbons are converted to CO2 and H2O
e.g. 2NO CO ———> N CO2
• leaded petrol must not pass through the catalyst as the lead
deposits on the catalyst’s surface and “poisons” it, thus blocking
sites for reactions to take place.

4. The internal combustion engine
Boardworks AS Chemistry
Alkanes
Alkanes with chain lengths of 6-9 carbon atoms are used as fuels
This releases carbon dioxide into the atmosphere:
nonane + oxygen → carbon dioxide + water
C9H20(g) O2(g) → 9CO2(g) H2O(g)
Although modern internal combustion engines are more efficient than in the past, incomplete combustion still occurs:
nonane + oxygen → carbon monoxide + water
2C9H20(g) O2(g) → 18CO(g) H2O(g)
Climate Change

5. Carbon dioxide in the atmosphere
Boardworks AS Chemistry
Alkanes
Burning fossil fuels releases carbon dioxide into the atmosphere.
Fossil fuels are being burned faster than they are being formed, which means that their combustion leads to a net increase in the amount of atmospheric carbon dioxide.
Photo credit: Andrew Horwitz / shutterstock.com
It has been suggested that increases in the amount of carbon dioxide and other greenhouse gases may be responsible for apparent changes to the climate.

6. CO2 is a greenhouse gas

7. CO2 emissions
From Wikipedia

8. Boardworks AS Chemistry Alkanes
Greenhouse gases
Carbon dioxide, water vapour and methane have been described as the main greenhouse gases.
This is because these have been suggested as the gases responsible for the majority of the greenhouse effect.
The greenhouse effect is a theory that has been suggested to explain apparent rises in the average temperature of the Earth.
Teacher notes
See the ‘Green Chemistry’ presentation for more information about greenhouse gases and global warming.
Increasing the amount of any of the greenhouse gases traps more heat energy from the Sun in the Earth’s atmosphere, raising the average temperature.

9. The Earth is getting warmer
From New Scientist

10. Sea levels are rising
From thesilentearth.com

11. Summary of Pollutant gases
Boardworks AS Chemistry
Alkanes
Summary of Pollutant gases

12. The combustion engine: nitrogen
Boardworks AS Chemistry
Alkanes
The temperature in engines can reach over 2000 °C. Here, nitrogen and oxygen, which at normal temperatures don’t react, combine to form nitrogen monoxide:
N2(g) + O2(g) → 2NO(g)
Nitrogen monoxide reacts further forming nitrogen dioxide:
2NO(g) + O2(g) → 2NO2(g)
Teacher notes
Students could be asked why nitrogen and oxygen require a high temperature to react. Important points are that nitrogen molecules contain a very strong triple bond, and that the activation energy for the reaction is very high.
Nitrogen dioxide gas reacts with rain water and more oxygen to form nitric acid, which contributes to acid rain:
4NO2(g) + 2H2O(l) + O2(g) → 4HNO3(aq)

13. Much SO2 from power stations
Catalytic converters in cars remove NOx

14. Sulfur contamination of fossil fuels
Boardworks AS Chemistry
Alkanes
Sulfur is found as an impurity in crude oil and other fossil fuels. It burns in oxygen to form sulfur dioxide:
S(s) + O2(g) → SO2(g)
Sulfur dioxide may be oxidized to sulfur trioxide:
2SO2(g) + O2(g) → 2SO3(g)
Both of these oxides dissolve in water forming acidic solutions
that fall from the clouds as Acid Rain:
SO2(g) + H2O(l) → H2SO3(aq)
SO3(g) + H2O(l) → H2SO4(aq)

15. Removing sulphur dioxide pollution
Boardworks AS Chemistry
Alkanes
Sulphur impurities are removed from fuel before it is burnt.
Removing the sulfur from coal before it is burnt is not practical.
Instead, the acidic sulfur oxides are removed from the waste gases using a base such as calcium oxide.
Photo credit: Ian Bracegirdle / shutterstock.com

16. Much SO2 from power stations, But wait
there is a solution
Much SO2 from power stations

17. Remove SO2 by flue gas desulphurisation
REMOVING SULPHUR
Much SO2 from power stations
CaO + SO2  CaSO3 or
CaCO3 + SO2  CaSO3 + CO2
Remove SO2 by flue gas desulphurisation

18. ACID RAIN
Damages plants

19. Branches from a tree in Germany's Black Forest show needle loss and yellowed boughs caused by acid rain

20. ACID RAIN ……Kills fish

21. Damages some stones (e.g. limestone)
1908
1968
ACID RAIN
Damages some stones (e.g. limestone)

22. CRACKING

24. Crude oil and Cracking
Lesson objective: To understand that alkane fuels are obtained from the fractional distillation, cracking and reforming of crude oil
Outcomes:
Describe the process of fractional distillation of crude oil
Describe thermal and catalytic cracking
Describe the reforming of crude oil
Explain why cracking is carried out
Explain why alkanes are reformed
Explain why the boiling points of different alkanes are different

25. Crude oil is a thick black viscous liquid that floats on water!
It was formed from the remains of sea animals and plants that died and were buried millions of years ago.
It is composed of a very large mixture of hydrocarbons

26. Oil refining involves the separation of these hydrocarbons into mixtures (‘fractions’) which are very important and extremely useful.
They are separated by fractional distillation
Liquids in a mixture can be separated if they have different boiling points.
Because there are so many hydrocarbon molecules in crude oil, the fractions contain groups of molecules will similar molecular masses.

27. Liebig condenser?
Fractioning column
round bottomed flask

28. fractions kerosene contains aviation fuel
residue contains tar, lubricating oil
gases contain methane, propane
fractions
Naphtha, the starting point for many other chemicals
gasoline contains petrol
gas oil contains diesel oil

29. some products obtained from the fractions
plastics
Bitumen,tar
wax
camping gas
petrol
domestic heating fuel
aviation fuel
industrial heating oil
diesel oil
fuel oil
lubricating oil

30. The most volatile fractions. (i. e
The most volatile fractions. (i.e. - those with lowest boiling point) come out of the top of the column and are gases, as these have very low molecular masses (e.g. methane).
The heaviest compounds fall to the bottom of the column.
These compounds have the highest molecular masses and are the least volatile.

31. From Wikipedia
Simple Distil (5 min. UK)
Fuse School (Frac Dis)

32. What is cracking? https://www.youtube.com/watch?v=sJArhELmiUk
Boardworks AS Chemistry
Alkanes
What is cracking?
Cracking is a process that splits long chain alkanes into shorter chain alkanes, alkenes and hydrogen.
Uses:
it increases the amount of gasoline and other economically important fractions
it increases branching in chains, an important factor for petrol's octane rating
Teacher notes
It could be emphasized to students that when cracking takes place, a mixture of products is produced from different cracking reactions occurring at the same time. The equation shown is just an example of a cracking reaction a C10H22 molecule may undergo. Although the reaction shown does not include hydrogen, the mixture of products will contain hydrogen due to reactions such as C10H22  C3H6 + C7H14 + H2
it produces alkenes and arenes, important feedstock for chemicals.
There are two main types of cracking: thermal and catalytic.

34. Catalytic Cracking

35. -162ºC -89ºC -42ºC -1ºC 36ºC What is the pattern here?
What does it have to do with homologues?
Why do we need to know this for fractionation?
-162ºC
-89ºC
-42ºC
-1ºC
36ºC

36. Catalytic Cracking
Uses something called a zeolite catalyst (hydrated aluminosilicate, Na2Al2Si3O. 2H2O), at a slight pressure and high temperature (about 450oC).
Using a catalyst cuts costs, because the reaction is faster at a lower temp and pressure.
Zeolite catalysts

37. Thermal cracking
Thermal means heat, it involves heating alkanes to a high temperature ( K),and putting them under high pressure, up to 7000kPa. WOW! That is a lot of Pressure! C H R - C H R - C H R = +
Catalytic cracking has almost completely
replaced thermal cracking. Why?

38. Aromatic hydrocarbons
PPT - GCSE - Crude oil
18-Jul-19
Thermal cracking
Catalytic cracking
Temperature
Pressure
Catalyst
Products
900C
450C
70 atm
1-2 atm
none
zeolites
Motor fuels
Aromatic hydrocarbons
Cyclic alkanes
Branched alkanes
alkenes

39. THE WINNER BY FAR Catalytic cracking…..why?
Boardworks AS Chemistry
Alkanes
THE WINNER BY FAR Catalytic cracking…..why?
Catalytic cracking BETTER because it:
1) produces a higher proportion of branched alkanes, that burn more easily than straight-chain alkanes, in petrol
2) Uses a lower temperature and pressure so it is cheaper
3) Produces a higher proportion of arenes, which are valuable feedstock chemicals.
Ok there is a bad piece of information, nothing is perfect :
Catalytic cracking cannot be used on all fractions, such as bitumen, the supply of which is great. Oh my, what an opportunity that is lost!!!
Teacher notes
Catalytic cracking is the main form of cracking used in the manufacture of petrol.

40. Boardworks AS Chemistry Alkanes
Supply and demand
Boardworks AS Chemistry
Alkanes
The demand for lower boiling point (shorter chain) fractions is greater than the proportion found in crude oil.
Crude oil contains too many higher boiling point (longer chain) fractions, which are in lower demand and are less economically valuable.
Photo credit: Dmitrijs Dmitrijevs / shutterstock.com
Teacher notes
Students could be asked to explain why shorter chain fractions are more useful than longer chain fractions. Cars raise the demand for fractions like gasoline, but crude oil contains more of the fractions like bitumen.
There is therefore a shortage of shorter chain fractions and a surplus of longer chain ones.