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The Haber Process

The Haber Process. Oops!!!. N 2(g) + 3 H 2(g) D 2 NH 3(g). A brief summary of the Haber Process. The Haber Process combines nitrogen from the air with hydrogen derived mainly from natural gas (methane) into ammonia. The reaction is reversible and the production of ammonia is exothermic.

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The Haber Process

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  1. The Haber Process

  2. Oops!!!

  3. N2(g) + 3 H2(g)D 2 NH3(g)

  4. A brief summary of the Haber Process • The Haber Process combines nitrogen from the air with hydrogen derived mainly from natural gas (methane) into ammonia. The reaction is reversible and the production of ammonia is exothermic. • N2(g) + 3 H2(g)D 2 NH3(g) DH = -92 kJ

  5. Some notes on the conditions N2(g) + 3 H2(g)D 2 NH3(g) DH = -92 kJ • Pressure • According to Le Chatelier’s Principle, should a high or low pressure favour the production of ammonia?

  6. Some notes on the conditions N2(g) + 3 H2(g)D 2 NH3(g) DH = -92 kJ • Pressure • A high pressure should favour the production of ammonia.

  7. Some notes on the conditions N2(g) + 3 H2(g)D 2 NH3(g) DH = -92 kJ • Pressure • Economic Considerations • The cost of maintaining a high pressure reaction system increases with the amount of pressure. The usual pressure is about 200 atmospheres.

  8. Some notes on the conditions N2(g) + 3 H2(g)D 2 NH3(g) DH = -92 kJ • Temperature • According to LeChatelier’s Principle, should a high or low temperature favour the production of ammonia?

  9. Some notes on the conditions N2(g) + 3 H2(g)D 2 NH3(g) DH = -92 kJ • Temperature • A low temperature favours the production of ammonia.

  10. Some notes on the conditions N2(g) + 3 H2(g)D 2 NH3(g) DH = -92 kJ • Temperature • Economic Considerations • An extremely low temperature slows the reactions so much that it takes too long for the system to produce much ammonia when starting with hydrogen and nitrogen. That is, it takes a long time to reach equilibrium.

  11. Some notes on the conditions N2(g) + 3 H2(g)D 2 NH3(g) DH = -92 kJ • Temperature • Economic Considerations • The temperature normally used is about 450oC

  12. Some notes on the conditions N2(g) + 3 H2(g)D 2 NH3(g) DH = -92 kJ • The Catalyst • Finely-divided iron is used. It has small amounts of magnesium and aluminum oxides added to increase its efficiency as a catalyst.

  13. Some notes on the conditions N2(g) + 3 H2(g)D 2 NH3(g) DH = -92 kJ • Recycling • At each pass of the gases through the reactor, only about 15% of the nitrogen and hydrogen converts to ammonia. (This figure also varies from plant to plant.) By continual recycling of the unreacted nitrogen and hydrogen, the overall conversion is about 98%.

  14. http://www.chemguide.co.uk/physical/equilibria/haber.htmlHaber process

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