Chemical products are indispensable for major branches of industry, for instance the pharmaceutical and automotive sector, as well as the plastics, food, agricultural or building materials industry. Both organic and inorganic raw materials are required here.
Many inorganic raw materials that are required in larger amounts and which cannot be found in nature are produced inexpensively using mass production plants in industrial chemistry. These include basic chemicals such as iron, from which steel is produced for the manufacture of machines and tools, or sodium carbonate (soda) as a cleaning agent.
The chemical production of iron from its ores goes back far into the past. The discovery of iron – and the tools or weapons that can be made from it – is so significant that historians have named this era the Iron Age. The importance of iron grew tremendously during the industrial revolution. In modern blast furnaces iron ore is reduced to iron in a multistage process involving the addition of atmospheric oxygen.
Another important process is the Solvay process – named after a Belgian chemist – for the production of sodium carbonate. Sodium carbonate and calcium chloride are derived from calcium carbonate and sodium chloride. As the reaction does not occur spontaneously, ammonia – as a sort of catalyst – is added in this cyclic process.
In the chlor-alkali process, sodium chloride is split into chlorine gas, sodium hydroxide and hydrogen by means of electrolysis. As these products are always produced in the same ratio, they are referred to as co-products.
The Haber-Bosch process was the first method to produce large amounts of ammonia. In this process, the nitrogen from the air is made to react with hydrogen at 500°C and 300 bar. According to Le Chatelier’s principle, the formation of ammonia is facilitated at high pressure (4 gas particles become 2 gas particles). An iron catalyst is necessary for the reaction to succeed.
N2 + 3 H2 → 2 NH3
The hydrogen required for this is produced in a synthesis gas reactor. Here methane – the main component of natural gas – is made to react with water to produce carbon monoxide and hydrogen.
CH4 + H2O → CO + 3 H2
The carbon monoxide is oxidised with atmospheric oxygen to form CO2 and then scoured to yield pure hydrogen. This can be used for ammonia synthesis.
The ammonia produced in this way is primarily used in the Ostwald process. Here ammonia is oxidised in several stages to form nitric acid.
NH3 + 2 O2 → HNO3 + H2O
Approx. 60% nitric acid results. This can be further processed into nitrates and fertilisers.