The doubling of the population on the earth requires humans to produce more food to support it. However, the space of the earth is fixed, and the land per capita will not increase. One way to solve the problem is to try to increase grain yield per acre. The growth of food crops requires phosphorus fertilizer, potassium fertilizer and nitrogen fertilizer. Without these fertilizers, it is difficult to have a good harvest. Therefore, the importance of various fertilizers and the key role of nitrogen fertilizers in various fertilizers are gradually recognized by people.
In the past, nitrogen fertilizers were used in large quantities in the form of sodium nitrate and ammonium sulfate. Due to the rapid increase in demand, people can't help but worry that sodium nitrate will soon be used up, and there will also be a shortage of ammonium sulfate. Therefore, the problem of nitrogen fixation has attracted great attention from the scientific community. Nitrogen makes up about 4/5 of the entire air on Earth. Although there is a large amount of free nitrogen in the air, the chemical properties of nitrogen are very inactive, making direct utilization difficult. Scientists have discovered that under normal temperatures in nature, free nitrogen can only be directly utilized by a type of bacteria that grows on leguminous plants, called rhizobia. Rhizobium has a wonderful ability, that is, it has the function of fixing nitrogen and can convert nitrogen in the air into the nitrogen fertilizer it needs at room temperature.
In 1902, Haber, a professor of chemistry at the Karlsruhe Institute of Engineering in Germany, began the epoch-making scientific research work of fixing nitrogen into nitrogen oxides and ammonia (the most common compound of nitrogen). Guided by the theory of chemical equilibrium, he began to experiment bit by bit and patiently. He once embedded a reaction vessel that could withstand hundreds of atmospheric pressures into a gun shell, used platinum, tungsten, uranium and other rare metal materials provided by the gas lamp company of the Amael Society, and risked high temperatures and high pressures to continuously experiment and find a new catalyst.
In 1907, Harper and others finally succeeded in obtaining ammonia, a nitrogen compound with 8.25%, under unusual high-pressure conditions of about 550°C and 150 to 250 atmospheres, and became the first For the first time, 0.1 kilogram of synthetic ammonia was successfully produced, making it possible for the development of synthetic ammonia to break through the laboratory and begin to enter the practical field and transform into industrial production.
In 1909, Harper proposed the concept of "circulation". The so-called "circulation" is to return the nitrogen and hydrogen that have not undergone chemical reaction to the reactor, and to separate the reacted ammonia through condensation. In this way, repeated operations can increase the yield of synthetic ammonia and make the process practical. The proposal of this concept can be said to be a decisive breakthrough in the process of industrialization of synthetic ammonia development technology.
In 1919, the Swedish Academy of Sciences considered that the synthetic ammonia invented by Haber had played a huge role in economic production, and decided to award Haber the world's highest scientific honor in 1918, the Nobel Prize in Chemistry. In recognition of his outstanding contributions to ammonia synthesis research. In his speech when receiving the award, Harper described the invention of ammonia as "turning stones into bread", which unexpectedly aroused the unanimous outrage of the scientific community around the world. Some commentators even linked Haber's invention to Germany's start of World War I, believing that his invention also greatly enhanced Germany's wartime explosives production capacity.
Whether Harper’s metaphor is appropriate or not, his invention did open up a way for humans to directly utilize free ammonia, and also created a chemical method for high-pressure synthesis of ammonia. Its significance is not only to turn the nitrogen in the atmosphere into an "inexhaustible and inexhaustible" cheap source for the production of chemical fertilizers, but also to bring about fundamental changes in agricultural production. At the same time, this invention also greatly promoted the development of related science and technology. For example, in 1923, the synthesis of methanol under 100 to 200 atmospheric pressure conditions; in 1926, artificial petroleum under 100 atmospheric pressure conditions; in 1937, high-pressure polyethylene production under 1,400 atmospheric pressure conditions, etc., are all related to the theory of ammonia synthesis. Establishment and development are related. From this point of view, Harper ushered in a new era of chemical research.