Earth Science: Material in Flux – From test Tube to Reactor
Before you can produce large quantities of a substance, you must first learn what reactions are needed to generate the substance and how those reactions can be scaled up for industrial production.
At the end of the 18th century, the French Academy of Sciences offered a prize for the development of a method for creating washing soda (sodium carbon- ate) from common salt (sodium chloride). Sodium carbonate was used in large quantities as a washing agent and for the pro- duction of glass. The process developed a few years later by Nicolas Leblanc (1742- 1806) was the beginning of the modern chemical industry, reducing the cost of producing soda to just one-ninth of the previous cost.
However, waste products resulting from the Leblanc process were bad for people’s health and a burden on the environment. Because of this, Leblanc’s process was replaced. Current environ- mental concerns, along with efficiency are important reasons to develop new production methods for chemical substances. Originally, sodium carbonate was also used to produce caustic soda (sodium hydroxide) and large amounts are still used worldwide—around 60 million tons yearly.
Caustic soda is produced by the electrolysis of sodium chloride. Through this method, sodium chloride is dissolved in water to become negatively charged chloride ions and positively charged sodium ions. The chloride ions move in water to a graphite rod, which is positively charged and connected to a power supply of direct current. Chlorine is formed when the chloride ions transfer their electrons to the positively charged rod, called the “anode.”
The power supply pumps the electrons from the anode to a negatively charged steel sheet, called the “cathode.” The electrons (e-) are transferred to water molecules (H2O) so that hydrogen (H2) and hydroxide ions (OH-) are formed according to the equation: 2 H2O + 2e- = 2OH – + H2. Caustic soda (sodium hydroxide in water) is formed from the hydroxide ions and the sodium ions. A technical difficulty lies in the fact that the cathode products of hydrogen and caustic soda have to be kept separate from the anode product of chloride in order to avoid undesired side reactions.
This process is chlorine-alkali electrolysis and has been continually improved over time. Reactions in micro-reactors, however, yield a substantially better product than reactions that take place in large agitating tubs. In addition, the integrity of the process is higher, since the reactions can be controlled in a targeted manner. The rate of producing chemicals can also be increased, meaning micro-reactors will be used more and more in industry.
Production of iron
An example of the difficult path between the discovery of a chemical reaction and its technical implementation is that of iron and steel. Iron has been extracted from iron ore in blast furnaces since the 14th century.
Only in the 18th century, when coke was used to bind oxygen to the iron ores, did iron become an important material. New methods of making iron are still being invented, in order to control the carbon content in iron as economically as possible.
HABER PROCESS FOR AMMONIUM
Ammonia is an important substance, and its derivatives are used in fertilizers and explosives At first, the synthesis of ammonium from nitrogen and hydrogen failed, however, early in the 20th century.
Fritz Haber (1868-1934) finally found that ammonium yield was increased if the reaction occurred under external pressure together with a catalyst to raise the rate of reaction.
CATALYSTS
chemical reactions start only after the activation energy level is reached. Catalysts lower the energy level required for this process. One of the best known catalysts is used in automobiles where it helps convert poisonous exhaust gases into harmless gases.
Catalysts are widely used in the chemical industry as they speed up industrial scale processes, even though they are not actually required for the reaction, saving on money and energy costs.