Ammonia manufacturing, uses in industry and Agriculture etc...

1. AMMONIA
By: Trishauna Milton

2. Objectives
Students should be able to:
1. Outline the steps in the manufacture of ammonia
from its elements, by the Haber process;
 Including the production of the starting materials
and manufacturing conditions.
 Apply the principles of chemical equilibrium and
kinetics.

3. Objectives continued
2. Discuss the uses of ammonia.
 In agriculture and chemical industry.
3. Assess the impact of the ammonia industry
on the environment.

4. What is Ammonia?
 Ammonia is a compound of Nitrogen and
Hydrogen with the formula NH3. It is a
colourless gas with a characteristic and
famous pungent smell.

5. The manufacturing of Ammonia
The Haber Process
The Haber Process is a method which is used
for the industrial preparation of ammonia
directly from nitrogen and hydrogen. It was
developed by the German chemist, Fritz
Haber.

6. The stages in the Haber process are as follows:
1. A mixture of nitrogen (1 volume) and hydrogen (3
volumes) is compressed.
2. the compressed gases pass into a converter (reactor
vessel), which contains trays of catalyst:
• The catalyst is iron (Fe) or a mixture of iron and iron
(III) oxide (the oxide gets reduced by the hydrogen to
iron). The iron is porous, so it has a large surface area
for the gases to react on. A promoter (usually
potassium hydroxide) is added to increase the
effectiveness of the catalyst.
• The temperature in the converter is usually about
400-450°C.

7. The pressure in the converter can range from 25-
200atmosphers (but 200 atmospheres is common).
Under these conditions up to 15% of the nitrogen and
hydrogen are converted to ammonia.
3. N2(g) + 3H2(g) 2NH3(g) ΔH° = -92kJ mol-1
4. The mixture passes into an expansion chamber. The
ammonia cools here and condenses. The ammonia is
removed as a liquid.
5. The unreacted nitrogen and hydrogen are returned to
the converter so they are not wasted.
NB. The ammonia is removed from the system as soon as
is formed to maintain the position of the equilibrium
the right. About 10% ammonia is produced per cycle
however a yield of about 98% is obtained by recycling
the gases.

8. A flow diagram of the Haber process

9. Raw materials for the Haber process
 The nitrogen is obtained from fractional distillation of
liquefied air while the hydrogen is derived mainly from
natural gas and water in steam reforming.
CH4(g) + H2O(g) 800°C CO(g) + 3H2(g)
20 atm
 The carbon monoxide produced which can poison the
catalyst used in the Haber Process is removed by reaction
with more steam.
CO(g) + H2O(g) CO2(g) + H2(g)

10.  The combination of nitrogen and hydrogen
into ammonia is a reversible reaction. The
forward reaction is exothermic and results in a
decrease in volume.
N2(g) + 3H2(g) 2NH3(g)
∆H= -92kJ mol-1

11. The best conditions for the Haber
process
 Effect of pressure
Ammonia production is favoured by an increase in pressure.
An increase in pressure shifts the equilibrium towards the
right. More product is formed. This is because according
to Le Chatelier’s Principle increasing the pressure shifts the
equilibrium in favour of fewer gaseous molecules. A
pressure between 25 and 200 atm is used, depending on
the plant. Although pressures above 200 atmospheres give
a higher yield, they are not used because:

12. A lot more energy is required to power the
compressors. This costs a lot more money.
At higher pressures the reaction vessels are less
safe. A lot more money would have to be spent to
make them strong enough to withstand the extra
pressure.
Effect of temperature
Ammonia production is favoured by lower
temperature. This is because the reaction is
exothermic. For an exothermic reaction an increase
in temperature decreases the value of KP so
decreases the yield of the forward, i.e. The yield of
ammonia. This is beacuse according to Le
Chatelier’s principle:

13. Decrease in temperature decreases the energy
of the surroundings.
The reaction goes in the direction in which
energy is released.
Energy is released in the exothermic reaction.
This favours the reactants.
Effect of catalyst
A catalyst does not affect the yield of
ammonia but does increase the rate at which
the product (ammonia) is formed.

14. The best conditions overall
The diagram above shows how the yield varies with temperature
and pressure.
When the temperature is increased:
• The rate of the reaction increases
• The equilibrium yield decreases.

15. There is a conflict between the best equilibrium
yield, which decreases with increase in temperature
and the best rate of reaction which increases with
increase in temperature. So we use compromise
conditions; a temperature of about 420-450°C is used
at 200 atmospheres with an iron catalyst to give a
reasonable yield at a fast enough rate.
Removing ammonia by condensing it helps improve
the yield. This is because removing ammonia as a
liquid shifts the position of equilibrium to the right in
favour of fewer molecules.

17. The uses of Ammonia in the agriculture
industry
 Fertilizers-a large amount of the ammonia
produced is used in the agriculture and fertilizer
industry. Ammonia can be applied to soil directly as
liquid ammonia or it can be used to produce
fertilizers such as urea, ammonium and nitrate
salts. Nitrogenous fertilizers provide a valuable
source of nitrogen which is necessary for healthy
plant growth.

19.  Ammonia and urea are also used in livestock feeds
as a source of protein.

20. The uses of Ammonia in the chemical
industry
 Ammonia is used to manufacture nitric acid which
is used to make explosives.

21. Ammonia is also used in the manufacture of:
 Pharmaceuticals
 Sodium Carbonate
 Plastics
 Paper
 Textiles

22. • Industrial refrigeration systems also use ammonia as a
refrigerant because it is easily liquefied by compression
or cooling and absorbs a large amount of heat from its
surroundings.
• Ammonia solutions are also widely used as commercial
and house hold cleaners.
• To make dyes.
• In treating textiles (especially cotton and wool) to alter
their properties.

24. The impact of the Ammonia industry on
the environment
Eutrophication
 Excess fertilizers in rivers and streams cause eutrophication. This is
a process whereby the excess nutrients in the water stimulate rapid
plant growth on the surface of the water. This enhanced plant
growth, often called algal bloom, prevents light from reaching
plants lower in the water. These plants die and bacteria use up the
dissolved oxygen in the water for decomposition. This results in the
death of fish and other aquatic animals which relies on oxygen for
respiration.

25. Smog
Ammonia in the atmosphere can combine with
nitrogen and sulphur oxides from vehicles and
industry to form fine particles which contribute to
smog.
Human Health Problems
Ammonia itself can irritate the lungs and inhibit
the uptake of oxygen by haemoglobin by altering
the pH of the blood. Ammonia can react with acids
in the atmosphere to form ammonium salts. These
exist as small particles (particulates). When
in over a period of time, these can cause
asthma, coughing fits and ‘farmer’s lung’.
Smog-fog or
haze
intensified by
smoke or
other
atmospheric
pollutants.
Farmer’s Lung
is a
hypersensitivit
y pneumonitis
induced by
the inhalation
of biologic
dusts coming
from hay dust
or mold
spores or
other
agricultural
products.

26. Soil acidification
When ammonia in the atmosphere reacts
with water in the soil it is converted to NH4
+
ions. NH4
+ ions are also present in fertilisers.
Excess NH4
+ ions are converted by bacteria
nitrites, nitrates and H+ ions. The H+ ions
make the soil acidic and plants may not be
able to grow well.

28. REFERENCES
 Maraj, S.& Samai, A. (2011). Chemistry For CAPE. Trinidad and Tobago:
Caribbean Educational Publishers.
 Norris, R., Barrett, L., Maynard-Alleyne, A.,& Murray, J., (2012). CAPE
Chemistry UNIT 2 Study Guide. United Kingdom: Nelson Thornes
Caribbean.
 https://www.slideshare.net/neethulalmini/industrial-preparation-of-
ammonia-1?qid=34679704-c259-4dcc-a4da-
0b82ac9ad686&v=&b=&from_search=11

29. QUESTIONS