The Haber Bosch process, which is also called the Haber process, is basically one of the most successful and efficient industrial procedures for ammonia production’>production. In the 20th century, a German chemist named Fritz Haber and his assistant developed the Haber process catalyst and high-pressure devices to carry out this process in a laboratory. Later, in 1910, Carl Bosch took the design and created a machine for the industrial-scale production of ammonia. Indeed, this was an essential development in the field of science.
Let us understand the process in detail.
Process and Conditions Explanation
The Haber Bosch process provides a good case study to demonstrate how the industrial chemists use their knowledge of the chemical equilibria affecting factors to find the best conditions that are required to produce a considerable yield of products at a fair rate.
In this process, “the N2 (atmospheric nitrogen) is converted to NH3 (ammonia) by reacting with H2 (hydrogen).”. In this process, a metal catalyst is used, and high pressures and temperatures are maintained.
The raw materials that are used for the process are listed below.
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Air, which supplies the nitrogen.
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Natural gas and water supply the hydrogen and the energy needed to heat the reactants.
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Iron is the catalyst and does not get used up in the reaction.
Let us have a look at the diagram given below.
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According to the diagram, in the Haber Bosch process, we obtain the nitrogen gas from the air and it combines with the hydrogen atom obtained from natural gas in a 1:3 ratio by volume.
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These gases are passed via 4 beds of catalyst, where the cooling takes place in each pass. This is performed to maintain the equilibrium constant.
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Different conversion levels take place in each pass where unreacted gases are recycled.
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Generally, iron is used as a catalyst in this process, and the complete procedure is conducted by maintaining a pressure of 150 – 200 atm and a temperature ranging from 400 – 450⁰C.
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This process also involves steps such as carbon dioxide removal, shift conversion, methanation, and steam reforming.
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Then, in the final stage of this process, the ammonia gas is cooled down to form a liquid solution. Then it is collected and stored in the containers.
Reaction Rate and Equilibrium
The Haber process for ammonia synthesis is based on the reaction of hydrogen and nitrogen. The chemical reaction can be represented below. It is an exothermic reaction, where energy is released. The Haber process equation is given below.
[N_2(g) + 3H-2(g) rightarrow 2NH_3(g)]
In this reaction, nitrogen is obtained by separating it from the air via liquefaction, and hydrogen is obtained from the natural gas by reforming or steam.
[CH_4(g) + H_2O rightarrow H_2(g) + CO(g)]
As per the principle of Le Chateleir, ammonia production is favoured by low temperature and high pressure. Typically, the Haber process is carried out at pressures ranging from 200-400 atmospheres and a temperature of 500⁰C. In commercial ammonia production, NH3 is continuously collected as it is produced. The product removal causes more hydrogen and nitrogen to combine as per Le Chatelier’s principle.
However, this is a reversible reaction, which is affected by changes in pressure, temperature, and catalyst used, mainly in the equilibrium mixture composition, and the reaction rate.
Catalyst Used in Haber Process
Iron can be used as a catalyst, but the catalyst used in the production is not pure iron. It contains potassium hydroxide as a promoter, added to it to increase its efficiency. Usually, this process takes place under high temperature and pressure.
Since the operating temperature is very low, the reaction rate can be increased by using the catalyst, which consists of finely divided the iron-containing molybdenum either as iron oxide or as a promoter.
A few key points are listed below.
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We can also use CaO, K2O, Al2O3, and SiO2 as promoters of iron instead of using potassium hydroxide.
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Almost, uranium was easier and effective to obtain than osmium.
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The original Haber process reaction chambers used osmium as the catalyst, but it was available in extremely small quantities.
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After extensive research, a much less expensive iron-based catalyst was discovered.
Uses of Ammonia
Ammonia is useful in many areas. A few uses of ammonia are as follows.
Ammonia can be used in making nitro-based explosives, like RDX, TNT, etc.
Ammonia is one of the main components in making fertilizers.
It can also be used in air-conditioning units in buildings, and large-scale refrigeration plants.
It can be used in manufacturing particular drugs such as antimalarials, sulfonamide, and also vitamins, including nicotinamide and thiamine.
Ammonia can also be used in different cleaning products and acts as an effective cleaning agent.
Did you know?
Why is Iron Used as a Catalyst in the Haber Process?
Iron can be used in the Haber process as a low-cost catalyst. Also, it allows an acceptable time to reach a reasonable yield.
How to Get Hydrogen for the Haber Process?
Methane formed from natural gas is the major source of hydrogen. In high pressure and temperature, the pipe inside a reformer has a nickel catalyst. The steam reforming process is carried out by separating the hydrogen and carbon atoms in the natural gas.