Ammonia (NH3) is a chemical compound of hydrogen with nitrogen. It got its name from the Greek word “hals ammniakos” or the Latin “sal ammoniacus” which translates lonely - “ammonia”. It is such a substance called ammonium chloride that was obtained in the Libyan desert in the oasis of Ammonium.
Ammonia is considered a very toxic substance that can irritate the mucous membranes of the eyes and respiratory tract. The primary symptoms of ammonia poisoning are profuse lacrimation, shortness of breath, and pneumonia. But at the same time, ammonia is a valuable chemical substance that is widely used to produce inorganic acids, for example, nitric, hydrocyanic, as well as urea and nitrogen-containing salts. Liquid ammonia is an excellent working substance in refrigerated containers and machines, as it has a high specific heat of vaporization. Aqueous solutions of ammonia are used as liquid fertilizers, as well as for the ammonization of superphosphates and fertilizer mixtures.
The production of ammonia from exhaust gases in the process of coal coking is the oldest and most affordable method, but today it is already outdated and practically not used.
The modern and main way is to obtain ammonia in industry based on the Haber process. Its essence is in the direct interaction of nitrogen and hydrogen, which proceeds as a result of the conversion of hydrocarbon gases. Natural gas, oil refining gases , associated petroleum gases, and residual gases from acetylene production are usually used as feedstock. The essence of the conversion method for producing ammonia is the decomposition of methane and its homologs at high temperature into components: hydrogen and carbon monoxide with the participation of oxidizing agents - oxygen and water vapor. At the same time, oxygen enriched air or atmospheric air is mixed into the convertible gas. Initially, the reaction of producing ammonia based on convertible gas proceeds with the release of heat, but with a decrease in the volume of the initial reaction products:
N2 + 3H2 ↔ 2NH3 + 45.9 kJ
However, the production of ammonia on an industrial scale is carried out using a catalyst and under artificially created conditions that allow to increase the yield of the finished product. In the atmosphere where ammonia is produced, the pressure rises to 350 atmospheres, and the temperature rises to 500 degrees Celsius. Under such conditions, the ammonia yield is about 30%. Gas is removed from the reaction zone using the cooling method, and nitrogen and hydrogen, which have not reacted, are returned to the synthesis column and can again participate in the reactions. During the synthesis, it is very important to clean the mixture of gases from catalytic poisons, substances that can nullify the effect of catalysts. Such substances are water vapor, CO, As, P, Se, O2, S.
Porous iron with impurities of aluminum and potassium oxides acts as a catalyst in the reactions of the synthesis of nitrogen and hydrogen. Only this substance, out of all 20 thousand previously tried, allows to achieve an equilibrium state of the reaction. This principle of ammonia production is considered the most economical.
The production of ammonia in the laboratory is based on the technology of displacing it from ammonium salts with strong alkalis. Schematically, this reaction is presented as follows:
2NH4CI + Ca (OH) 2 = 2NH3 ↑ + CaCl2 + 2H2O
or
NH4Cl + NaOH = NH3 ↑ + NaCl + H2O
To remove excess moisture and drain ammonia, it is passed through a mixture of caustic soda and lime. Obtaining very dry ammonia is achieved by dissolving metallic sodium in it and subsequent distillation of the mixture. Most often, such reactions are carried out in a closed metal system under vacuum. Moreover, such a system must withstand high pressure, which is achieved by the released vapors of ammonia, up to 10 atmospheres at room temperature.