Without catalyst, the activation energy of ammonia synthesis is very high, about 335kJ/mol. After adding iron catalyst, the reaction is divided into two steps: nitridation and nitrogen hydrogenation. The activation energy of the first stage is126 kj/mol ~167 kj/mol, and that of the second stage is 13kJ/mol.
German chemist F. Haber (1868- 1934) began to study the direct synthesis of ammonia from nitrogen and hydrogen. 1908 applied for a patent, that is, the "recycling method". On this basis, he continued his research and improved the synthesis at 1909, and the ammonia content reached more than 6.
This method is a direct synthesis method widely used in industry. In order to solve the problem of low conversion rate of hydrogen and nitrogen in the reaction process, after the synthesis reaction, the ammonia product was separated from the gas, and the unreacted gas was mixed with fresh hydrogen and nitrogen to participate in the synthesis reaction again.
Extended data:
Importance of the reaction between hydrogen and ammonia;
Ammonia is one of the important inorganic chemical products and occupies an important position in the national economy. About 80% of ammonia is used to produce chemical fertilizer, and 20% is the raw material of other chemical products. Ammonia is mainly used to make nitrogen fertilizer and compound fertilizer, such as urea, ammonium nitrate, ammonium phosphate, ammonium chloride and various nitrogen-containing compound fertilizers, all of which are based on ammonia. As an industrial raw material and ammoniated feed, ammonia accounts for about12 of the world output. ?
Nitric acid, various nitrogen-containing inorganic salts, organic intermediates, sulfonamides, polyurethane, polyamide fibers, nitrile rubber, etc. all directly need ammonia as raw materials.
Liquid ammonia is often used as a refrigerant, and some commercial ammonia stored and transported is transported to other places by manufacturers in liquid form.
In addition, in order to ensure the balance between supply and demand between synthetic ammonia and ammonia processing workshops in the factory and prevent production from being stopped due to short-term accidents, it is necessary to set up a liquid ammonia warehouse. There are three types of liquid ammonia storage: non-freezing, semi-freezing and full freezing. Liquid ammonia can be transported by sea, barge, pipeline, tanker and truck.
References:
Baidu encyclopedia-synthetic ammonia