The Frank–Caro process, also called cyanamide process, is the

nitrogen fixation Nitrogen fixation is a chemical process by which molecular dinitrogen () is converted into ammonia (). It occurs both biologically and abiological nitrogen fixation, abiologically in chemical industry, chemical industries. Biological nitrogen ...

reaction of

calcium carbide Calcium carbide, also known as calcium acetylide, is a chemical compound with the chemical formula of . Its main use industrially is in the production of acetylene and calcium cyanamide. The pure material is colorless, while pieces of technica ...

with

nitrogen gas Nitrogen is a chemical element; it has symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at seventh i ...

in a reactor vessel at about 1,000 °C. The reaction is

exothermic In thermodynamics, an exothermic process () is a thermodynamic process or reaction that releases energy from the system to its surroundings, usually in the form of heat, but also in a form of light (e.g. a spark, flame, or flash), electricity (e ...

and self-sustaining once the reaction temperature is reached. Originally the reaction took place in large steel cylinders with an electrical resistance element providing initial heat to start the reaction. Modern production uses rotating ovens. The synthesis produces a solid mixture of

calcium cyanamide Calcium cyanamide, also known as Calcium carbondiamide, Calcium cyan-2°-amide or Calcium cyanonitride is the inorganic compound with the formula CaCN2. It is the calcium salt of the cyanamide () anion. This chemical is used as fertilizer and is c ...

(CaCN₂), also known as nitrolime, and

carbon Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...

. :CaC₂ + N₂ → CaCN₂ + C

History

The Frank–Caro process was the first commercial process that was used worldwide to fix atmospheric nitrogen. The product was used as

fertilizer A fertilizer or fertiliser is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from liming materials or other non-nutrient soil amendments. Man ...

and commercially known as ''Lime-Nitrogen''. ''Nitrolim'' or ''Kalkstickstoff'' in German. The method was developed by the German chemists Adolph Frank and Nikodem Caro between 1895 and 1899. In its first decades, the world market for inorganic fertilizer was dominated by factories utilizing the cyanamide process.

Production facilities

The first full-scale factories were established in 1905 in Piano d´Orta (Italy) and Westeregeln (Germany). From 1908 the Frank–Caro process was used at ''North Western Cyanamide Company'' at

Odda Odda () is a list of former municipalities of Norway, former municipality in the old Hordaland counties of Norway, county, Norway. The municipality existed from 1913 until its dissolution in 2020 when it was merged into Ullensvang Municipality i ...

, Norway. With an annual production capacity of 12,000 ton from 1909, the factory at Odda was by far the largest in the world. At this time, first phase factories were established in

Briançon Briançon (, ) is the sole Subprefectures in France, subprefecture of the Hautes-Alpes Departments of France, department in the Provence-Alpes-Côte d'Azur Regions of France, region in Southeastern France. It is the highest city in France at an a ...

(France),

Martigny Martigny (; , ; ) is the capital city of the district of Martigny (district), Martigny, cantons of Switzerland, canton of Canton of Valais, Valais, Switzerland. It lies at an elevation of , and its population is approximately 20,000 inhabitants ( ...

(Switzerland),

Bromberg Bydgoszcz is a city in northern Poland and the largest city in the historical region of Kuyavia. Straddling the confluence of the Vistula River and its left-bank tributary, the Brda, the strategic location of Bydgoszcz has made it an inland ...

(

Prussia Prussia (; ; Old Prussian: ''Prūsija'') was a Germans, German state centred on the North European Plain that originated from the 1525 secularization of the Prussia (region), Prussian part of the State of the Teutonic Order. For centuries, ...

Poland Poland, officially the Republic of Poland, is a country in Central Europe. It extends from the Baltic Sea in the north to the Sudetes and Carpathian Mountains in the south, bordered by Lithuania and Russia to the northeast, Belarus and Ukrai ...

) and Knapsack (Germany). The cyanamide factory at Odda ceased operation in 2002. It is still intact and is a Norwegian candidate to the

UNESCO World Heritage List World Heritage Sites are landmarks and areas with legal protection under an international treaty administered by UNESCO for having cultural, historical, or scientific significance. The sites are judged to contain "cultural and natural heritag ...

Haber process

In the 1920s the more energy-efficient

Haber process The Haber process, also called the Haber–Bosch process, is the main industrial procedure for the ammonia production, production of ammonia. It converts atmospheric nitrogen (N2) to ammonia (NH3) by a reaction with hydrogen (H2) using finely di ...

gradually took over in the nitrogen fertilizer production, but Frank-Caro process has continued to produce a useful chemical feedstock. In 1945 the production of calcium cyanamide reached a peak of an estimated 1.5 million tons a year.

Patent

German patent nr. DE 88363 (1895)

References

External links