Catalytic oxidation of ammonia

Industrially nitrogen monoxide is prepared by the catalytic oxidation of ammonia as an intermediate in the manufacture of nitric acid (p. 238). The molecule of nitrogen monoxide contains an odd number of electrons and can be represented as... 

On the large scale, nitric acid is now made in large quantities by the catalytic oxidation of ammonia, employing the reaction ... 

A major step in the production of nitric acid [7697-37-2] (qv) is the catalytic oxidation of ammonia to nitric acid and water. Very short contact times on a platinum—rhodium catalyst at temperatures above 650°C are required. 

Hydroxylamine sulfate is produced by direct hydrogen reduction of nitric oxide over platinum catalyst in the presence of sulfuric acid. Only 0.9 kg ammonium sulfate is produced per kilogram of caprolactam, but at the expense of hydrogen consumption (11). A concentrated nitric oxide stream is obtained by catalytic oxidation of ammonia with oxygen. Steam is used as a diluent in order to avoid operating within the explosive limits for the system. The oxidation is followed by condensation of the steam. The net reaction is... 

In 1838, Frederic Kuhlmann discovered die formation of nitrogen oxide (NO) during die catalytic oxidation of ammonia. Wilhelm Ostwald developed die production mediods in 1902 and established die base for today s major commercial processes. However, industrial production began only after Haber and Bosch developed the synthesis of ammonia around 1916. 

Nitric oxide is the simplest thermally stable odd-electron molecule known and, accordingly, its electronic structure and reaction chemistry have been very extensively studied. The compound is an intermediate in the production of nitric acid and is prepared industrially by the catalytic oxidation of ammonia (p. 466). On the laboratory scale it can be synthesized from aqueous solution by the mild reduction of acidified nitrites with iodide or ferrocyanide or by the disproportionation of nitrous acid in the presence of dilute sulfuric acid ... 

Nitric acid is one of the three major acids of the modem chemical industiy and has been known as a corrosive solvent for metals since alchemical times in the thirteenth centuiy. " " It is now invariably made by the catalytic oxidation of ammonia under conditions which promote the formation of NO rather than the thermodynamically more favoured products N2 or N2O (p. 423). The NO is then further oxidized to NO2 and the gases absorbed in water to yield a concentrated aqueous solution of the acid. The vast scale of production requires the optimization of all the reaction conditions and present-day operations are based on the intricate interaction of fundamental thermodynamics, modem catalyst technology, advanced reactor design, and chemical engineering aspects of process control (see Panel). Production in the USA alone now exceeds 7 million tonnes annually, of which the greater part is used to produce nitrates for fertilizers, explosives and other purposes (see Panel). 

Nitric Add by the Oxidation of Ammonia. Here, the catalytic oxidation of ammonia under press using a Pt catalyst maintained at a temp of 900—1000° is the process used. The reaction press is the rate determining step, being directly proportional to the product nitric acid concn (Refs 6, 22, 26, 30, 34, 36, 37 41). 

HA can be produced by catalytic oxidation of ammonia with hydrogen peroxide or by catalytic reduction of nitrates with hydrogen . Analogously, oxidative and reductive enzymic pathways in which HA is produced from either ammonia or nitrate have been identified in a variety of biological systems. 

Currently, nitric acid is manufactured exclusively by catalytic oxidation of ammonia. Platinum or platinum-rhodium is an effective catalyst of this oxidation (Ostwald process). Three basic steps in such ammonia oxidation process are (1) oxidation of ammonia to form nitric oxide ... 

Platinum also is used extensively as a catalyst in hydrogenation, dehydrogenation, oxidation, isomerization, carbonylation, and hydrocracking. Also, it is used in organic synthesis and petroleum refining. Like palladium, platinum also exhibits remarkable abdity to absorb hydrogen. An important application of platinum is in the catalytic oxidation of ammonia in Ostwald s process in the manufacture of nitric acid. Platinum is installed in the catalytic converters in automobile engines for pollution control. 

Masimilla and Johnstone studied the catalytic oxidation of ammonia ... 

Nitric oxide is commercially produced by the catalytic oxidation of ammonia using a platinum catalyst 4NH3(g) + 50 —> 4NO(g) + 6H20(g). Nitrous oxide is produced by the thermal decomposition of ammonium nitrate at approximately 240°C NH4N03(g) —> N O + 2H . ... 

The catalytic oxidation of ammonia by air over platinum gauze at 900 °C gives nitric oxide (reaction 9.12), which is then oxidized to nitric acid by air and liquid water in a nitrous gas absorber (reactions 9.13 and 9.14) ... 

Catalytic oxidation of ammonia to nitric oxide is the basis of production of nitric acid. It is also used in other processes, of which may be mentioned hydroxylamine synthesis (Section XIII) and the chamber process for the production of sulfuric acid. The products of the reaction are nitric oxide, water, and nitrogen, so that the reaction can be described by the equation... 

Ostwald process The production of nitric acid by the catalytic oxidation of ammonia, overall order The sum of the powers to which individual concentrations are raised in the rate law of a reaction. Example If the rate = [S02][S03]" l/2, then the overall order is f. 

The catalytic oxidation of ammonia to NH2OH, followed by the non-catalyzed condensation of NH2OH with the ketone ... 

E. C. C. Baly and H. M. Duncan studied the decomposition of ammonia by means of a hot platinum wire. Two types of ammonia may be prepared—an inactive and an active modification—which are decomposed to different extents by the same quantity of energy. The active form is obtained by the slow withdrawal of ammonia from a cylinder containing the compressed gas by warming the cone. aq. soln. and drying the gas by quicklime and by isothermal evaporation of the liquefied gas at its b.p. The inactive form is obtained by the rapid evaporation of the liquefied gas. The inactive gas slowly recovers its activity on remaining in contact with the liquefied gas. The same effect can be produced by gently warming the gas by means of a platinum wire heated at 200°. In order to observe these phenomena, the platinum wire must be activated in the same way as is customary in W. Ostwald s process for the catalytic oxidation of ammonia in air to nitric acid. Alternatively,... 

Another way is direct catalytic oxidation of ammonia with dioxygen ... 

Researchers returned to the oxidation of ammonia in air, (recorded as early as 1798) in an effort to improve production economics. In 1901 Wilhelm Ostwald had first achieved the catalytic oxidation of ammonia over a platinum catalyst. The gaseous nitrogen oxides produced could be easily cooled and dissolved in water to produce a solution of nitric acid. This achievement began the search for an economic process route. By 1908 the first commercial facility for production of nitric acid, using this new catalytic oxidation process, was commissioned near Bochum in Germany. The Haber-Bosch ammonia synthesis process came into operation in 1913, leading to the continued development and assured future of the ammonia oxidation process for the production of nitric acid. 

So far as domestic production of nitric acid is concerned, only one process need be considered since all but a very small quantity of the nitric acid produced in this country is made by the catalytic oxidation of ammonia. In addition, a little-used method and one obsolete method are discussed briefly. 

The Ostwald process is the basis for the modem family of processes that make nitric acid by the catalytic oxidation of ammonia. Wilhelm Ostwald, a German physical chemist, discovered it in 1900. The process was used by Germany during World War I to make explosives after the Allied blockade cut off the regular German supply of nitrites from Chile and other places96. 

The major deposits of alkali nitrates found in Chile were vital for making nitric acid, which is necessary to prepare almost all types of explosives and propellants. Of course, nitric acid is now obtained by the catalytic oxidation of ammonia by the Ostwald process (see Chapter 12). 

Commercially it is obtained by catalytic oxidation of ammonia as already noted. Direct combination of the elements occurs only at very high temperatures, and to isolate the small amounts so formed (a few volume percent at 3000°C) the equilib-... 

The K-L model, because of its greater simplicity, thus seems to be the model of choice for systems with smaller bubbles. In this paper we shall show how the K-L model can be used to predict the experimental results obtained by Massimilla and Johnstone (1961) on the catalytic oxidation of ammonia. It will be seen that the performance of their system was largely controlled by reaction limitations within the bed s phases. The effects of various parameters on bed performance are examined for such a reaction-limited system, and then the effects of these parameters for a transport-limited system are also discussed. Finally, we consider the effect of using average values of the bubble diameter and transport coefficients on model predictions. 

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