Ostwald ammonia synthesis

As to efforts to carry out ammonia synthesis in a technical direction, studies along that line had been started in the B. A. S. F. after Wilhelm Ostwald had suggested such work in 1900. In laboratory experiments considerable yields of synthetic ammonia had been obtained by W. Ostwald (27). However, all attempts to reproduce these yields on a larger scale were futile, and finally Ostwald had to admit that in his original experiments, ammonia had probably been erroneously introduced into the synthesis reactor with a foreign source, presumably in form of an iron nitride, which had been formed by a previous treatment of the iron catalyst with ammonia. 

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. 

Around 1900 Fritz Haber began to investigate the ammonia equilibrium [11] at atmospheric pressure and found minimal ammonia concentrations at around 1000 °C (0.012 %). Apart from Haber, Ostwald and Nernst were also closely involved in the ammonia synthesis problem, but a series of mistakes and misunderstandings occurred during the research. For example, Ostwald withdrew a patent application for an iron ammonia synthesis catalyst because of an erroneous experiment, while Nernst concluded that commercial ammonia synthesis was not feasible in view of the low conversion he found when he first measured the equilibrium at 50 - 70 bar [12] - [14],... 

Nitric acid is currently almost exclusively produced by the catalytic oxidation of ammonia using the Ostwald process (1902). The reaction of sodium nitrate (Chile niter, the only nitrate occurring naturally in large quantities) with sulfuric acid, operated at the turn of the century, has not been economic since the emergence of the Haber-Bosch ammonia synthesis process shortly before World War 1. The... 

Selectivity control by competitive adsorption also explains how the platinum catalyst works in the Ostwald process, the oxidation of ammonia to nitrogen oxide, used to produce nitrates from ammonia. The low reactivity of platinum causes the rate of ammonia dissociation on platinum to be low. The dissociation of N-H bonds of ammonia is the reverse of the ammonia synthesis discussed in the previous section. Whereas the rate of dissociative NH3 adsorption is relatively small, the initial sticking coefficient for dissociative oxygen adsorption is higher, about 0.01. 

Haber s work on ammonia synthesis began during the summer of 1904 not because of any planned, determined effort to solve an elusive task, but because of an unexpected request from the Osterreichische Chemische Werke in Vienna, a company set up by the brothers O. and R. Margulies. Haber did not immediately take up the offer he advised the brothers to take what was at that time the easiest route and recover by-product ammonia from coking. As he knew something about Ostwald s earlier work on the problem (but not about his unsuccessful deal with BASF and about the withdrawal of Ostwald s 1900 patent application), he wrote to him hoping that he would cooperate with the Margulies brothers. 

In yet another series of chance events, Haber s return to work on ammonia synthesis was prompted by a peculiar case of scientific rivalry, by one man s publicly tactless behavior injuring other man s pride. Hermann Walther Nernst (1864-1941) was only four years older than Haber, but by the time of their clash in 1907 he was certainly better established and better known (fig. 4.3). One of Ostwald s pupils from Leipzig, he became the first professor of physical chemistry in Gottingen in 1894, and his pioneering contributions ranged from technical inventions (Nernst s lamp and electrical piano, neither of which was a commercial success) to the theory of heterogeneous reactions. ... 

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. 

C15-0098. The first step in the Ostwald process for the synthesis of nitric acid is the combustion of ammonia ... 

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. 

The importance of catalysts in chemical reactions cannot be overestimated. In the destruction of ozone previously mentioned, chlorine serves as a catalyst. Because of its detrimental effect to the environment, CFCs and other chlorine compounds have been banned internationally. Nearly every industrial chemical process is associated with numerous catalysts. These catalysts make the reactions commercially feasible, and chemists are continually searching for new catalysts. Some examples of important catalysts include iron, potassium oxide, and aluminum oxide in the Haber process to manufacture ammonia platinum and rhodium in the Ostwald synthesis of nitric... 

This reaction is used for the synthesis of nitric acid in the Ostwald process (see Section 7.8.1). Without catalysts, and at higher temperatures, ammonia bums in an oxygen atmosphere with a pale yellow flame forming the thermodynamically favorable products dinitrogen and water (AH = -1267kJmol ). At high pressures, mixtures of ammonia and oxygen are explosive. 

Most of the modem manufacture of nitric acid is done by the catalytic oxidation of ammonia (Ostwald process). Other now outdated processes include the reaction of sodium nitrate with sulfuric acid and direct synthesis from N2 and 02 by the arc process at temperatures in excess of 2,000°C. Once cheap ammonia became available these processes were no longer economical. 

Synthesis of ammonia from N2 and H2 (Haber—Bosch process) Oxidation of ammonia (Ostwald process)... 

The fixation of atmospheric nitrogen through both the electric arc and calcium cyanamide routes were thus put into commercial practice. Both processes suffered from large requirements of electrical energy for the synthesis and were replaced before long by the direct synthesis of ammonia from its elements, which has become known as the Haber-Bosch process. Since Ostwald had developed a method for the oxidation of ammonia to produce nitric acid at the beginning of the century (1902), synthetic ammonia provided the basis for an industrial route to nitric acid. 

Pritz Haber s successful synthesis of ammonia a few years before the First World War had a profound impact on world history. Nitric acid and nitrates are essential in the manufacture of fertilizers and explosives. Haber s synthesis of ammonia without impurities made it possible to manufacture nitric acid by the Ostwald process. Unfortunately the first major application of ammonia production was manufacture of explosives which prolonged the war. 

The direct production of nitric oxide from air at high temperatures in an electric arc by the Birkeland and Eyde or Cyanamide processes was feasible, but could only be used in locations with abrmdant and cheap hydroelectric power. This clearly was not the long term answer, and a series of significant advances initiated by Ostwald at Leipzig, following discussions with William Pfeffer, soon followed. Ostwald, himself, worked on the catalytic synthesis of ammonia, and its oxidation to nitric acid. 

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