http://www.daviddarling.info/images/Haber_process.jpg
http://www.hydro.com/upload/4518/haberbosh_en.jpg
http://www.wisegeek.com/what-is-the-haber-bosch-process.htm
http://chemgeneration.com/milestones/the-haber-bosch-process.html
http://www.britannica.com/EBchecked/topic/250771/Haber-Bosch-process
Sunday, June 30, 2013
Economic and Rate Conditions
Temperature:
The reaction becomes slower as the temperature becomes lower.
You need the gases to reach equilibrium within the very short time that they will be in contact with the catalyst in the reactor.
400 - 450°C is a compromise temperature producing a reasonably high proportion of ammonia in the equilibrium mixture (even if it is only 15%), but in a very short time.
Pressure
Increasing the pressure brings the molecules closer together. The higher the pressure the better in terms of the rate of a gas reaction.
Very high pressures are very expensive to produce on two counts.
You have to build extremely containment vessels and strong pipes to withstand the very high pressure. That increases your capital costs when the plant is built.
High pressures cost a lot to produce and maintain. That means that the running costs of your plant are very high. 200 atmospheres is a compromise pressure chosen on economic grounds. The cost of generating the pressure exceeds the price you can get for the extra ammonia produced, if the pressured used is too high.
The reaction becomes slower as the temperature becomes lower.
You need the gases to reach equilibrium within the very short time that they will be in contact with the catalyst in the reactor.
400 - 450°C is a compromise temperature producing a reasonably high proportion of ammonia in the equilibrium mixture (even if it is only 15%), but in a very short time.
Pressure
Increasing the pressure brings the molecules closer together. The higher the pressure the better in terms of the rate of a gas reaction.
Very high pressures are very expensive to produce on two counts.
You have to build extremely containment vessels and strong pipes to withstand the very high pressure. That increases your capital costs when the plant is built.
High pressures cost a lot to produce and maintain. That means that the running costs of your plant are very high. 200 atmospheres is a compromise pressure chosen on economic grounds. The cost of generating the pressure exceeds the price you can get for the extra ammonia produced, if the pressured used is too high.
The Process
Haber-Bosch Process:
The Haber process takes nitrogen gas from air and combines it with molecular hydrogen gas to form ammonia gas. This is an exothermic reaction, meaning it releases energy so that the sum of the enthalpies of N2 and H2 (the reactants) is greater than the enthalpy of NH3 (the products).
N2(g) + 3H2(g) → 2NH3(g)
The Haber process incorporates Le Chatlier's Principle, which is a good example of equilibrium principles. Uses of Le Chatlier's Principle are reversible reactions involving gases. Chemical equilibrium is when a reaction has no tendency to change the quantity of the reactants and products, so the reaction can go both ways.
1. Increasing the pressure and decreasing the temperature causes a move of the reaction to the right which results in the higher yield of ammonia.
2. When the pressure is increased, the system adapts to the change by moving the molecules left to right to decrease the overall pressure, because there are more molecules on the left side than the right side.
3. For temperature, it moves from right to left when the temperature drops is because of the process being exothermic, where heat is released.
4. The system adjusts to lessen the change, so it would make more heat to compensate for the energy lost, since that is the product of this. More ammonia would be made if more energy were made. If the temperature was increased to speed up the reaction, it would produce a smaller amount of ammonia yield.
N2 (g) + 3H2 (g) ↔ 2NH3 (g) -Examples of Le Chatlier's principle using this reaction.
1. If the volume is decreased here, it has the same result as when the pressure is decreased.
2. If the pressure is increased, in this equation, it will move right because there are fewer gas molecules are produced going to the right then the backwards one.
The Haber process takes nitrogen gas from air and combines it with molecular hydrogen gas to form ammonia gas. This is an exothermic reaction, meaning it releases energy so that the sum of the enthalpies of N2 and H2 (the reactants) is greater than the enthalpy of NH3 (the products).
N2(g) + 3H2(g) → 2NH3(g)
The Haber process incorporates Le Chatlier's Principle, which is a good example of equilibrium principles. Uses of Le Chatlier's Principle are reversible reactions involving gases. Chemical equilibrium is when a reaction has no tendency to change the quantity of the reactants and products, so the reaction can go both ways.
1. Increasing the pressure and decreasing the temperature causes a move of the reaction to the right which results in the higher yield of ammonia.
2. When the pressure is increased, the system adapts to the change by moving the molecules left to right to decrease the overall pressure, because there are more molecules on the left side than the right side.
3. For temperature, it moves from right to left when the temperature drops is because of the process being exothermic, where heat is released.
4. The system adjusts to lessen the change, so it would make more heat to compensate for the energy lost, since that is the product of this. More ammonia would be made if more energy were made. If the temperature was increased to speed up the reaction, it would produce a smaller amount of ammonia yield.
N2 (g) + 3H2 (g) ↔ 2NH3 (g) -Examples of Le Chatlier's principle using this reaction.
1. If the volume is decreased here, it has the same result as when the pressure is decreased.
2. If the pressure is increased, in this equation, it will move right because there are fewer gas molecules are produced going to the right then the backwards one.
Conditions of the Process
Catalyst
The catalyst is actually a little more complicated than pure iron. It has potassium hydroxide added to it as a promoter and potassium hydroxide increases efficiency.
Pressure
The pressure of the process varies from one plant to another, but usually is always high.
Recycling
At each pass of the gases through the reactor, only 15% of the hydrogen and nitrogen converts to ammonia. By continual recycling of the not reacted nitrogen and hydrogen, the overall conversion is about 98%
The mixture of nitrogen and hydrogen going into the reactor is in the ratio of 1 volume of nitrogen to 3 volumes of hydrogen.
Avogadro's Law says that equal volumes of gases at the same pressure and temperature must contain equal numbers of molecules. That means that the gases are going into the reactor in the ratio of 1 molecule of nitrogen to 3 of hydrogen.
The catalyst is actually a little more complicated than pure iron. It has potassium hydroxide added to it as a promoter and potassium hydroxide increases efficiency.
Pressure
The pressure of the process varies from one plant to another, but usually is always high.
Recycling
At each pass of the gases through the reactor, only 15% of the hydrogen and nitrogen converts to ammonia. By continual recycling of the not reacted nitrogen and hydrogen, the overall conversion is about 98%
The mixture of nitrogen and hydrogen going into the reactor is in the ratio of 1 volume of nitrogen to 3 volumes of hydrogen.
Avogadro's Law says that equal volumes of gases at the same pressure and temperature must contain equal numbers of molecules. That means that the gases are going into the reactor in the ratio of 1 molecule of nitrogen to 3 of hydrogen.
What Is the Haber-Bosch Process?
Sometimes regarded as the most important technological advance of the 20th century, The Haber-Bosch Process(Haber Process) allows the economical mass synthesis of ammonia (NH3) from nitrogen and hydrogen. This unique process was developed a little before World War I by Fritz Haber and Carl Bosch, who were German chemists. Haber won the Nobel Prize for Chemistry in 1918 for his discoveries, and Bosch shared a Nobel Prize with Friedrich Bergius in 1931 for his work on high-pressure chemical reactions.
A flow scheme for the process is demonstrated below.
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