How is Iron Used to Make Ammonia?

Iron, specifically in the form of iron powder, can be used as a catalyst in a process to generate ammonia (NH₃). The process involves nitrogenating the iron powder and then reacting it with hydrogen.

Here's a breakdown of the process:

1. Nitrogenation: Iron powder is milled with nitrogen gas (N₂), leading to the formation of nitrogenated iron particles. This process essentially prepares the iron surface to be more reactive with hydrogen.

2. Ammonia Synthesis: Hydrogen gas (H₂) is then passed over these nitrogenated iron particles. This reaction leads to the formation of ammonia. An example highlights that at 2 atmospheres of pressure and 45 °C, the resulting gas stream can contain a significant concentration of ammonia (82.5% by volume).

3. Catalyst Reusability: The residual iron powder remaining after the ammonia synthesis can be reused in subsequent cycles, making the process more efficient.

In summary, iron acts as a catalyst by first reacting with nitrogen to form an intermediate, which then facilitates the reaction with hydrogen to produce ammonia. This allows for ammonia synthesis under specific conditions.