The synthesis of ammonia by the Haber process
Looking through the records of the Nobel Prize in Chemistry, you can see that there were no awards from 1916 to 1917, because during this period, Europe was After experiencing the first World War, the prize was awarded in 1918. The Chemistry Prize was awarded to the German chemist Haber. This aroused discussion among scientists. Some scientists from Britain, France and other countries publicly expressed their opposition. They believed that Hubble was not qualified to receive this honor. Why is this?
With the development of agriculture, the demand for nitrogen fertilizer is growing rapidly. Before the
19th century, the source of nitrogen fertilizer required in agriculture mainly came from
organic by-products, such as manure, seed cake and green manure.
A large sodium nitrate deposit was discovered in Chile in 1809 and was quickly exploited. On the one hand, this mineral deposit is limited, and on the other hand, the military industry also requires a large amount of saltpeter to produce explosives. Therefore, another way must be found to solve the source of nitrogen fertilizer. Some far-sighted chemists pointed out: Considering the future food problem, in order to save future generations from starvation, we must hope that scientists can achieve atmospheric nitrogen fixation. Therefore, fixing the abundant nitrogen in the air and converting it into a usable form became a major issue that attracted the attention and concern of many scientists at the beginning of the 20th century.
Haber is one of the chemists engaged in experimental and theoretical research on the process conditions of ammonia synthesis.
The industrial production of ammonia using nitrogen and hydrogen as raw materials was once a difficult subject. It took about 150 years from the first laboratory development to industrial production.
. In 1795, someone tried to synthesize ammonia under normal pressure, and later someone tried it at 50 atmospheres, but they all failed.
In the second half of the 19th century, great progress in physical chemistry made people realize that the reaction of synthesizing ammonia from nitrogen and hydrogen is reversible. Increasing the pressure will push the reaction in the direction of producing ammonia: increasing the temperature will push the reaction towards the formation of ammonia. The reaction moves in the opposite direction, but the temperature is too low and the reaction rate is too small; the catalyst will have an important impact on the
reaction. This actually provides theoretical guidance for ammonia synthesis experiments. At that time, the authority of physical chemistry, Nernst of Germany, clearly pointed out that nitrogen and hydrogen can synthesize ammonia under high pressure conditions, and provided some experimental data. The French chemist Le Chateau was the first
to attempt to conduct a high-pressure ammonia synthesis experiment. However, the mixture of nitrogen and hydrogen mixed with oxygen caused an explosion, and he gave up this dangerous experiment
Verify. Haber, who had a good foundation in physical and chemical research, was determined to overcome this daunting problem.
Harbin first conducted a series of experiments to explore the optimal physical and chemical conditions for ammonia synthesis. Some of the data he obtained in the experiment were different from Nernst's. He did not blindly follow authority, but relied on experiments to test, and finally confirmed that Nernst's calculations were wrong. With the assistance of Rosenno, a student from the UK, Haber successfully designed a set of equipment suitable for high-pressure experiments and a process flow for synthesizing ammonia. This flow is:
Blowing water vapor over hot coke can produce a mixture of almost equal volumes of carbon monoxide and hydrogen. The carbon monoxide further reacts with water vapor under the action of the catalyst to obtain carbon dioxide and hydrogen. Then the mixed gas is dissolved in water under a certain pressure, and the carbon dioxide is absorbed, thus producing purer hydrogen. Similarly, when water vapor is mixed with an appropriate amount of air and passed through red-hot carbon, the oxygen and carbon in the air will
generate carbon monoxide and carbon dioxide, which will be absorbed and removed, thus obtaining the required nitrogen.
The mixed gas of nitrogen and hydrogen synthesizes ammonia under high temperature, high pressure and the action of a catalyst. But what kind of high temperature and high pressure conditions are
optimal? What kind of catalyst is best? This still requires a lot of effort to explore.
With a spirit of perseverance and constant experiments and calculations, Haber finally achieved inspiring results in 1909. This means that under the conditions of a high temperature of 600C, a pressure of 200 atmospheres and osmium as a catalyst
, synthetic ammonia with a yield of about 8% can be obtained. A conversion rate of 8% is not high, and will certainly affect the economic benefits of production. I am afraid that the ammonia synthesis reaction
cannot achieve a conversion rate as high as that of sulfuric acid production. In sulfuric acid production, the conversion rate of sulfur dioxide oxidation reaction is almost close to 100%. What to do
? Haber believes that this process is feasible if the reaction gas can be circulated under high pressure and the ammonia generated by the reaction is continuously separated from this cycle. So he successfully designed the recycling process of raw gas. This is the Haha method of synthesizing ammonia.
Going out of the laboratory and carrying out industrial production will still require hard work. After Haber applied for a patent for the process he designed, he handed it over to Germany's largest chemical company at the time, the Baden Aniline and Soda Ash Manufacturing Company. This company originally planned to use the arc method to produce oxygen and nitrogen, and then synthesize ammonia. Comparing the two, the company immediately canceled the original plan and organized engineering and technical personnel headed by chemical expert Bosch to put Haber's design into practice.
First of all, according to Harbin's process flow, they found a more reasonable method to produce a large amount of cheap raw materials nitrogen and hydrogen. Through experiments, they realized that although osmium is a very good catalyst, it is difficult to process because it is easily converted into volatile tetraoxides when it comes into contact with air. , In addition, there are very few reserves of this rare metal in the world. The second catalyst suggested by Harbin is uranium. Not only is uranium expensive, it's also sensitive to trace amounts of oxygen and water. In order to find an efficient and stable catalyst, they conducted as many as 6,500 experiments and tested 2,500 different formulas in two years, and finally selected an iron catalyst containing lead and magnesium accelerator. Developing suitable high-voltage equipment is also key to the process. At that time, low carbon steel could withstand
200 atmospheres of pressure, but it was afraid of decarburization and corrosion by hydrogen. Bosch thought of many ways, and finally decided to add a layer of wrought iron to the low carbon steel reaction tube. Although wrought iron has no strength, it is not afraid of hydrogen corrosion, which finally solved the problem.
Haber's idea of ??ammonia synthesis was finally realized in 1913, and a synthetic ammonia plant with a daily output of 30 tons was built and put into operation. Since then, ammonia synthesis has become a rapidly developing and very active part of the chemical industry. The creation of the synthetic ammonia production method not only opened up a way to obtain fixed nitrogen, but more importantly, the realization of this production process had a significant impact on the development of the entire chemical process. The research on synthetic ammonia comes from correct theoretical guidance. In turn, the research and testing of synthetic ammonia production technology promotes the development of scientific theories. In view of the realization of industrial production of synthetic ammonia and the promotion of the development of chemical theory by its research, it was correct to decide to award the Nobel Prize in Chemistry to Haber. Harper's acceptance of this award is well-deserved.
Some British and French scientists believe that Haber is not eligible to win the Nobel Prize. Why? Some people once believed that without the establishment of the ammonia industry, Germany would not have sufficient arms reserves, and the military would not dare to rashly launch World War I. With the synthetic ammonia industry, ammonia can be oxidized into nitrate to ensure the production of gunpowder. Otherwise, gunpowder cannot be guaranteed solely by relying on Chilean saltpeter. Of course, scientists have no direct responsibility for certain scientific inventions and creations being used in unjust wars. The criticism of Haber by the British and French scientific circles focused more on Haber's performance in the First World War.
In 1906, Haber became a professor of chemistry at the University of Karlsruhe. In 1911, he was appointed director of the Wilhelm Institute for Physical Chemistry and Electrochemistry near Berlin.
He also served as the Berlin Institute of Physics. University professor.
When the World War broke out in 1914, the blind patriotic enthusiasm stirred up by national chauvinism deeply involved Harper in the whirlpool of the old war. The laboratory he led became an important military institution serving the war: Haber undertook the supply and development of materials needed for the war, especially in the development of war gases. He once mistakenly believed that poison gas attacks were a good way to end the war and shorten the war's duration, so he served as the scientific person in charge of Germany's poison gas warfare during the war.
According to Harbin's suggestion, in January 1915, the German army placed cylinders containing chlorine gas at the front of the position and used wind to blow the chlorine gas toward the enemy positions.
The first field trial was successful. On April 22 of that year, during the Battle of Ypres launched by the German army, on a 6-kilometer-wide forward position, within 5 minutes
The German army released 180 tons of chlorine gas, a yellow-green poisonous gas about the height of a person. Using the force of the phoenix, they rushed along the ground towards the British and French positions (chlorine gas has a greater specific gravity than air, so it sank in the lower layer and moved along the ground), entered the trenches and stayed there. This poisonous wave caused the British and French troops to feel pain in their noses and throats, and then some people suffocated to death. The British and French soldiers were so frightened that they panicked and fled in all directions. It is estimated that about 15,000 British and French troops were poisoned. This was the beginning of modern chemical warfare using lethal poisons on a large scale in military history. Since then, both sides of the war have used poison gas, and the types of poison gas have been developed in new ways. Even the German authorities had not estimated the casualties caused by poison gas. However, the use of poisonous gas and chemical warfare was unanimously condemned by the people in various European countries. Scientists even criticized this inhumane behavior. In view of this, scientists from Britain, France and other countries naturally opposed awarding Haber the Nobel Prize in Chemistry. Harper was also greatly shaken mentally. Not long after the war ended, he fled to the countryside for about half a year for fear of being regarded as a war criminal.
The First World War ended with Germany's defeat in 1919. Some time after the war, Harper designed a plan to extract gold from seawater. It was hoped that this would be used to pay the war reparations demanded by the Allies. Unfortunately, the gold content in seawater was much less than people imagined at the time, and his efforts were in vain. Thereafter, through reflection on the war, he devoted all his energy to scientific research. Under his effective leadership, the Wilhelm Institute for Physical Chemistry became one of the world's academic centers for chemical research. Based on many years of experience in scientific research, he pays special attention
to creating an environment for his colleagues to be free from bias and able to conduct independent research. In his research, he also emphasizes theoretical research and applied research
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Research combined. As a result, his institute has become a first-class scientific research unit and has trained many high-level researchers. In order to change the disgraceful impression left by the war, he actively worked to strengthen the ties between scientific research institutions in various countries and the friendly exchanges between scientists from various countries. Nearly half of the members in his laboratory come from all over the world. The friendly reception and warm guidance not only won him understanding from the scientific community, but also increased his prestige.
However, tragedy soon struck him again. Haber was born on December 9, 1868 in Brislau, Germany (now Wraoclaw, Poland) to a Jewish businessman family. In 1933, after Hitler usurped power in Germany and established fascist rule, he began to implement the farce of so-called "Aryan science" with the mission of destroying "Jewish science", even though Haber was a famous scientist. , but because he was a Jew, he was brutally persecuted like other Jews. The fascist authorities ordered the dismissal of all Jews in the scientific and educational sectors. Fritz Haber
The great chemist was renamed: "Jew. Haber", that is, Jewish Haber. The Wilhelm Institute he headed was also reorganized.
Harper solemnly declared on April 30, 1933: "For more than 40 years, I have chosen my collaborators based on knowledge and moral standards, rather than considering him.
Our nationality and nation, for the rest of my life, it is impossible for me to change the way I think is so intact." Subsequently, Haber was forced to leave for her. Having served the motherland for decades, he is now living in a foreign land. First, he was invited by the University of Cambridge in England to work in Bobo's laboratory. Four months later, the Schiff Institute in Israel hired him to lead physical chemistry research there. But on the way to the Schiff Institute, Harbin suffered a heart attack and died in Switzerland on January 29, 1934.
Although Harbin was forced to leave Germany, the German scientific community and people have not forgotten him. On the first anniversary of his death, many societies and scholars in Germany
, despite the obstruction of the Nazis, organized rallies one after another to commemorate this great scientist.