Fixation of nitrogen

FIG. Noncatalytic gas phase reactions, a) Steam cracking of light hydrocarbons in a tnhnlar fired heater, (h ) Pehhle heater for the fixation of nitrogen from... 

Before 1900 the large-scale production of nitric acid was based entirely on the reaction of concentrated sulfuric acid with NaNOa and KNOj (p. 407). The first successful process for making nitric acid directly from Ni and O2 was devised in 1903 by E. Birkeland and S. Eyde in Norway and represented the first industrial fixation of nitrogen ... 

Fixation of nitrogen in solution in the presence of transition metal complexes. A. E. Shilov, Russ. Chem. Rev. (Engl. Transl.), 1974, 43,378-398 (161). 

When nitrogen and oxygen gases were present then it was possible to get fixation of nitrogen with the formation of nitrogen oxides. Molecules of nitrogen and oxygen dissociated in the cavitation bubbles to form initially NO radicals [33, 34]. 

In addition to photocleavage of water with photocatalysts, other photosynthetic processes such as photochemical C02 reduction, resulting in the formation of CO or methane, and the photochemical fixation of nitrogen are of great interest ... 

The most noteworthy multistage element cycles in which bacteria play important roles are the nitrogen and sulfur redox cycles. The fixation of nitrogen is a reductive process that provides organisms with nitrogen in a form usable for the synthesis of amino acids, nucleic acids, and other cell constituents. In essence, the overall conversion to the key intermediate, ammonia, can be represented as ... 

It is clear from these experiments that the presence of ethylene catalyses the fixation of nitrogen in lithium complexes. This assisted complexation was also observed with methyl-substituted ethylene and butadiene. It is a characteristic property of lithium-alkene complexes, as experiments performed with other lithium complexes have so far not yielded such ternary complexes. If one can easily anticipate that the fractional positive charge on the lithium in LiC2H4 and Li(C2H4)2 facilitates the coordination of N2 with, presumably, a a-donation to lithium, and possibly, to a weaker extent, p-donation from the metal, it is difficult to rationalize why LiC2H2 and LiC2H4 behave so differently with respect to nitrogen, for instance. 

In all these studies which were carried out over the five-year period, 1904-1909, the effects of catalysts on these fixations of nitrogen were investigated. For the barium compounds, iron oxide acted as a catalyst. For the titanium nitrides, various other metal oxides as well as a number of inorganic salts proved to be effective. For the silicium nitrides and aluminum nitrides, again metal oxides and salts had beneficial effects but in other proportions and to another extent than found for the titanium nitrides. Often, two or more catalysts were added to the reaction mixtures with beneficial effects, but no systematic quantitative comparisons were carried out at this time. Table I lists some of these experiments. 

A technical exploitation of these experiments appeared unattractive, until 1909. Other methods of the chemical fixation of nitrogen, particularly the electric arc process for the formation of nitrous oxides (18) and the calcium cyanamide process (19) appeared far superior at that time. 

The decomposition of lignin is caused by oxidation and demethylation furthermore, fixation of nitrogen occurs. Nitrogen can be derived from peptides, amino acids, or ammonia. AD these compounds can be formed by the decomposition of plant proteins or during the autolysis of the microorganisms. 

In such vessels granular or lumpy material moves vertically downward as a mass. The solid may be a reactant or a catalyst or a heat carrier. The reactor of Figure 17.28(a) was used for the fixation of nitrogen in air at about 4000°F. The heat-carrying pebbles are heated by direct contact with combustion gases, dropped into a reaction zone supplied with reacting air, and then recycled with elevators to the reheating zone. The treated air must be quenched... 

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