Industrial synthesis of ammonia

As an example, consider the industrial synthesis of ammonia (NH3). Ammonia is made by the Haber process, a single chemical reaction between molecules of hydrogen (H2) and nitrogen (N2) Although it is simple, this synthesis has immense industrial importance. The United States produces more than 16 billion kilograms of ammonia annually. 

In heterogeneous catalysis, the catalyst provides a surface on which the reactants are adsorbed. The chemical bonds of the reactants become weakened on the catalytic surface and new compounds ate formed. These compounds (products) have weaker bonds with the catalyst and consequently are released. An example of heterogeneous catalysis is the industrial synthesis of ammonia, which requires solid catalysts to obtain significant rates of reaction between nitrogen and hydrogen ... 

PROBLEM 8.24 Is the Haber process for the industrial synthesis of ammonia spontaneous or nonspontaneous under standard conditions at 25°C At what temperature (°C) does the changeover occur ... 

In the early 1900s, the German chemist Fritz Haber discovered that a catalyst consisting of iron mixed with certain metal oxides causes the reaction to occur at a satisfactory rate at temperatures where the equilibrium concentration of NH3 is reasonably favorable. The yield of NH3 can be improved further by running the reaction at high pressures. Typical reaction conditions for the industrial synthesis of ammonia are 400-500°C and 130-300 atm. 

What factors determine the direction and extent of a chemical reaction Some reactions, such as the combustion of hydrocarbon fuels, go almost to completion. Others, such as the combination of gold and oxygen, occur hardly at all. Still others—for example, the industrial synthesis of ammonia from N2 and H2 at 400-500°C— result in an equilibrium mixture that contains appreciable amounts of both reactants and products. 

The hydrogen used for about 90% of the industrial synthesis of ammonia comes from the following reaction at high temperature ... 

The NH3 can then be further converted into nitrate or nitrite or directly used in the synthesis of amino acids and other essential compounds. This reaction takes place at 0.8 atm N2 pressure and ambient temperatures in Rhizobium bacteria in nodules on the roots of legumes such as peas and beans, as well as in other independent bacteria. In contrast to these mild conditions, industrial synthesis of ammonia requires high temperatures and pressures with iron oxide catalysts, and even then yields only 15% to 20% conversion of the nitrogen to ammonia. Intensive efforts to determine the bacterial mechanism and to improve the efficiency of the industrial process have so far been only moderately successful the goal of approaching enzymatic efficiency on an industrial scale is still only a goal. 

M. Bowker, I. Parker, and K.C. Waugh. The Application of Surface Kinetic Data to the Industrial Synthesis of Ammonia. Surf. Sci. 197 L223 (1988). 

The complex interactions among social, economic, and political necessities are well illustrated by the development of the industrial synthesis of ammonia. The need for an industrial process for nitrogen fixation was recognized as early as 1890. Scientists in England noted that the world s future food supply would be determined by the amount of nitrogen compounds... 

Brot ms Lttft Bread out of air) Fritz Haber, Referring to his discovery of the industrial synthesis of ammonia. 

Nitrogen, N2, is fixed (converted to compounds) by bacteria, by lightning,and by the industrial synthesis of ammonia. Fixed nitrogen is used by plants and enters the food chain of animals. Later, plant and animal wastes decompose. Denitrifying bacteria complete the cycle by producing free nitrogen again. 

The industrial synthesis of ammonia is based on the reaction above. Which factor(s) will increase the equilibrium concentration of ammonia ... 

What has been the most important technical invention of the twentieth century Airplanes, nuclear energy, space flight, television, and computers are the most common answers. Yet none of these inventions has been as fundamentally important as the industrial synthesis of ammonia from its elements. Lives of the world s 6 billion people might be actually better without Microsoft Windows and 600 TV channels, and neither nuclear reactors nor space shuttles are critical determinants of human well-being. But the single most important change affecting the world s population— its expansion from 1.6 billion people in 1900 to today s 6 billion—would not have been possible without the synthesis of ammonia. 

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