The Haber Process

The production of ammonia by the Haber Process utilises all four factors that affect equilibrium reactions  

Only 15 20% of the gases react each time that they pass through the reactor unreacted hydrogen and nitrogen are recycled, with more being fed in to maintain the pressure. Once started, the process is continuous until the whole plant is closed for maintenance. 

Diatomic nitrogen makes up about 79 percent of Earth s atmosphere. A few species of soil bacteria can use atmospheric nitrogen to produce ammonia (NH3). Other species of bacteria then convert the ammonia into nitrite and nitrate ions, which can be absorbed and used by plants. Ammonia also can be synthesized. 

The process produces high yields of ammonia by manipulating three factors that influence the reaction—pressure, temperature, and catalytic achon. 

During the synthesis of ammonia, four molecules of reactant produce two molecules of product. According to Le Chatelier s principle, if the pressure on this reaction is increased, the forward reaction will speed up to reduce the stress because two molecules exert less pressure than four molecules. Increased pressure will also cause the reactants to collide more frequently, thus increasing the reaction rate. Haher s apparatus used a pressure of 2 X 10 kPa. 

The forward reaction is favored by a low temperature because the stress caused by the heat generated hy the reaction is reduced. But low temperature decreases the number of collisions between reactants, thus decreasing the rate of reaction. Haher compromised hy using an intermediate temperature of about 450°C. 

A catalyst is used to decrease the activation energy and thus, increase the rate at which equi-lihrium is reached. Haher used iron as a catalyst in his process. 

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This reaction is an undesirable side reaction in the manufacture of hydrogen but utilised as a means of removing traces of carbon monoxide left at the end of the second stage reaction. The gases are passed over a nickel catalyst at 450 K when traces of carbon monoxide form methane. (Methane does not poison the catalyst in the Haber process -carbon monoxide Joes.)... 

The process is as follows ammonia gas (made by the Haber process) is liquefied under pressure, to freeze out any water, and the anhydrous gas is then passed together with dust-free air through a... 

Ammonia (NH3) is the most important commercial compound of nitrogen. It is produced by the Haber Process. Natural gas (methane, CH4) is reacted with steam to produce carbon dioxide and hydrogen gas (H2) in a two step... 

Industrially, production is either from the Haber process at high pressure ... 

An even more effective homogeneous hydrogenation catalyst is the complex [RhClfPPhsfs] which permits rapid reduction of alkenes, alkynes and other unsaturated compounds in benzene solution at 25°C and 1 atm pressure (p. 1134). The Haber process, which uses iron metal catalysts for the direct synthesis of ammonia from nitrogen and hydrogen at high temperatures and pressures, is a further example (p. 421). 

It is estimated that each year approximately 150 million tonnes of nitrogen are fixed biologically compared to 120 million tonnes fixed industrially by the Haber process (p. 421). In both cases N2 is converted to NH3, requiring the rupture of the N=N triple bond which has the highest dissociation energy (945.41 kJmol )... 

The Haber process, represented by this equation, is now the main source of fixed nitrogen. Its feasibility depends on choosing conditions under which nitrogen and hydrogen react rapidly to give a high yield of ammonia. At 25°C and atmospheric pressure, the position of the equilibrium favors the formation of NH3 (K= 6 x 105). Unfortunately. however, the rate of reaction is virtually zero. Equilibrium is reached more rapidly by raising the temperature. However, because... 

Effect of Temperature and Pressure on the Yield of Ammonia in the Haber Process (PH2 = 3PNl)... 

Ammonia is one of the most important industrial chemicals more than ten million tons of NH3 are produced annually in the United States. You will recall (Chapter 12) that it is made by the Haber process... 

In an important industrial process for producing ammonia (the Haber Process) the overall reaction is... 

The Haber process for the synthesis of ammonia is one of the most significant industrial processes for the well-being of humanity. It is used extensively in the production of fertilizers as well as polymers and other products, (a) What volume of hydrogen at 15.00 atm and 350.°C must be supplied to produce 1.0 tonne (1 t = 10 kg) of NH3 (b) What volume of hydrogen is needed in part (a) if it is supplied at 376 atm and 250.°C ... 

FIGURE 9.17 The Haber process is still used to produce almost all the ammonia manufactured in the world. This pie chart shows how the ammonia is used. The figures are percentages. Note that 80%— as shown by the green band—is used as fertilizer, either directly or after conversion into another compound. 

The reactant is adsorbed on the catalyst s surface. As a reactant molecule attaches to the surface of the catalyst, its bonds are weakened and the reaction can proceed more quickly because the bonds are more easily broken (Fig. 13.36). One important step in the reaction mechanism of the Haber process for the synthesis of ammonia is the adsorption of N2 molecules on the iron catalyst and the weakening of the strong N=N triple bond. 

Each year, about half the 3 X 108 kg of hydrogen used in industry is converted into ammonia by the Haber process (Section 9.12). Through the reactions of ammonia, hydrogen finds its way into numerous other important nitrogen compounds such as hydrazine and sodium amide (see Section 15.2). 

By far the most important hydrogen compound of a Group 15/V element is ammonia, NH., which is prepared in huge amounts by the Haber process. Small quantities of ammonia are present naturally in the atmosphere as a result of the... 

NH3. Ammonia is a colorless gas. It is a strong base, forms hydrogen bonds, is soluble in water, and is a fairly reactive molecule. Each year 12.4 million metric tons are manufactured by the Haber process (N2 + 3H2 2NH3 at 400°C and 250 atm), principally for nitric acid production, which is then used to make fertilizers and explosives. As a fertilizer, ammonia can be utilized in three ways first by direct injection... 

The Haber process for ammonia manufacture, which operates above the critical point 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. 

C04-0069. Most of the ammonia produced by the Haber process is used as fertilizer. A second important use of NH3 is in the production of nitric acid, a top-15 industrial chemical. Nitric acid is produced by... 

C04-0074. Ammonia is produced industrially using the Haber process N2 + 3 H2 2 NH3 Suppose that an industrial reactor is charged with 75.0 kg each of N2 and H2. Use a table of amounts to determine what mass of ammonia could be produced if the reaction went to completion. 

As an indispensable source of fertilizer, the Haber process is one of the most important reactions in industrial chemistry. Nevertheless, even under optimal conditions the yield of the ammonia synthesis in industrial reactors is only about 13%. This Is because the Haber process does not go to completion the net rate of producing ammonia reaches zero when substantial amounts of N2 and H2 are still present. At balance, the concentrations no longer change even though some of each starting material is still present. This balance point represents dynamic chemical equilibrium. 

In this chapter, we present basic features of chemical equilibrium. We explain why reactions such as the Haber process cannot go to completion. We also show why using catalysts and elevated temperatures can accelerate the rate of this reaction but cannot shift Its equilibrium position in favor of ammonia and why elevated temperature shifts the equilibrium In the wrong direction. In Chapters 17 and 18, we turn our attention specifically to applications of equilibria. Including acid-base chemistry. 

Much of the ammonia S3mthesized by the Haber process is used to make HNO3. Ammonia and air are u i j j j Ptgauze,1200 K... 

C16-0019. Refer to Examples and. List four changes in conditions that might be used to increase the yield of ammonia in the Haber process. 

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