Industrial Preparation of Ammonia

From Ammonical Liquor

During the destructive distillation of coal, ammonical liquor is obtained as a by-product. Ammonical liquor on further processing yields large quantities of ammonia and ammonium salts.

Ammonical liquor is boiled with milk of lime to obtain ammonia. This is passed into ice-cold water, to form liquor ammonia.

If instead of water, ammonia is passed into hydrochloric, sulphuric or nitric acid, ammonium chloride or ammonium sulphate or ammonium nitrate are obtained respectively.

Haber's Process

Ammonia is manufactured by Haber's process using nitrogen and hydrogen (Fig.6.4).

Reactants: Nitrogen gas -1 volume and hydrogen gas -3 volumes

Conditions

Temerature	Pressure	Catalyst	Promotor
450°-500° C	152000-684000 mm of Hg	Iron	Molybdenum

 

The reaction in Habers process is exothermic and so external heating is not required once the reaction starts. Lowering the temperature to 450^o - 500^oC favours the reaction, but lowering the temperature below 450^o - 500^oC brings down the yield.

Note:-

Nitrogen is obtained in large scale from air. Air free from dust and carbon dioxide is cooled under high pressure and low temperature to about 200^oC and then allowed to warm. As nitrogen has lower boiling point (-169^oC) as compared to oxygen (-183^oC) it turns to gas leaving oxygen in liquid state.

Nitrogen can also be obtained by heating ammonium nitrite (in small amounts)

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