Ammonia (NH3) is a chemicalcompound of hydrogen with nitrogen. It got its name from the Greek words “hals ammniakos” or Latin “sal ammoniacus” which are translated lonely - “salary”. It is this substance called ammonium chloride that was obtained in the Libyan desert in the Ammonium oasis.
Ammonia is considered to be a very toxic substance.which can irritate the mucous membranes of the eyes and respiratory tract. The primary symptoms of ammonia poisoning are profuse tearing, 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, hydrogen cyanide, as well as urea and nitrogen-containing salts. Liquid ammonia is an excellent working substance of refrigerated containers and machines, as it has a high specific heat of evaporation. Aqueous solutions of ammonia are used as liquid fertilizers, as well as for the ammonization of superphosphates and fertilizer mixtures.
Getting ammonia from flue gases in the process of coking coal is the oldest and very affordable method, but today it is outdated and almost never used.
The modern and main way isAmmonia production in industry based on the Haber process. Its essence is in the direct interaction of nitrogen and hydrogen, which occurs as a result of the conversion of hydrocarbon gases. Natural gas, refinery gases, associated petroleum gases, and residual gases from acetylene production usually act as feedstock. The essence of the method of conversion obtaining ammonia is the decomposition of methane and its homologues at high temperature into its components: hydrogen and carbon monoxide with the participation of oxidizing agents - oxygen and water vapor. At the same time, air enriched with oxygen or atmospheric air is mixed with the convertible gas. Initially, the reaction of obtaining ammonia based on the convertible gas proceeds with the evolution of heat, but with a decrease in the volume of the initial reaction products:
N2 + 3H2 ↔ 2NH3 + 45.9 kJ
However, commercial production of ammoniais carried out using a catalyst and under artificially created conditions that allow to increase the yield of the finished product. In an atmosphere where ammonia production takes place, the pressure increases to 350 atmospheres, and the temperature rises to 500 degrees Celsius. Under these conditions, the yield of ammonia is about 30%. The gas is removed from the reaction zone using the cooling method, and nitrogen and hydrogen that have not reacted, are returned back to the synthesis column and can again participate in the reactions. During the synthesis, it is very important to clean the gas mixture from catalytic poisons, substances that can nullify the effect of catalysts. Such substances are water vapor, CO, As, P, Se, O2, S.
As a catalyst in nitrogen synthesis reactionsand hydrogen acts porous iron with impurities of aluminum oxide and potassium. Only this substance, from all 20 thousand previously tried, allows to achieve an equilibrium state of the reaction. This principle of ammonia production is considered the most economical.
Getting ammonia in the laboratory is based on the technology of displacing it from the ammonium salts of strong alkalis. Schematically, this reaction is as follows:
2NH4CI + Ca (OH) 2 = 2NH3 + CaCl2 + 2H2O
or
NH4Cl + NaOH = NH3 + NaCl + H2O
To remove excess moisture and dry out ammonia, itspassed through a mixture of caustic soda and lime. The production of ammonia very dry is achieved by dissolving metallic sodium in it and then distilling 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 evaporating ammonia vapor, up to 10 atmospheres at room temperature.
