Nitrogen oxidation and reduction

Figure 13 Relationships between three pathways of inorganic nitrogen oxidation and reduction (Wrage et ai, 2001) (reproduced by permission of Elsevier from Soil Biol Biochem. 2001, 33, 1723-1732).

If the acid of the ammonium salt is an oxidising agent, then on heating the salt, mutual oxidation and reduction occurs. The oxidation products can be nitrogen or one of its oxides and the reactions can be explosive, for example ... 

Heteropolyacids (HPA) are the unique class of inorganic complexes. They are widely used in different areas of science in biochemistry for the precipitation of albumens and alkaloids, in medicine as anticarcinogenic agents, in industry as catalysts. HPA are well known analytical reagents for determination of phosphoms, silica and arsenic, nitrogen-containing organic compounds, oxidants and reductants in solution etc. 

Scheme 1.4 Oxidation and reduction of reactive nitrogen species.

Now, GC-IRMS can be used to measure the nitrogen isotopic composition of individual compounds [657]. Measurement of nitrogen isotope ratios was described by Merritt and Hayes [639], who modified a GC-C-IRMS system by including a reduction reactor (Cu wire) between the combustion furnace and the IRMS, for reduction of nitrogen oxides and removal of oxygen. Preston and Slater [658] have described a less complex approach which provides useful data at lower precision. Similar approaches have been described by Brand et al. [657] and Metges et al. [659]. More recently Macko et al. [660] have described a procedure, which permits GC-IRMS determination of 15N/14N ratios in nanomole quantities of amino acid enantiomers with precision of 0.3-0.4%o. A key step was optimization of the acylation step with minimal nitrogen isotope fractionation [660]. 

These settlements cover 99 refineries in 29 states and on full implementation will result in annual emissions reductions of more than 87,000 tons of nitrogen oxides and more than 250,000 tons of sulfur dioxide. 

The same technology nsed in a catalytic converter was the starting point for use of additives to reduce NO in FCC nnits. The ability of these metal oxide materials to store and release oxygen affects the oxidation and reduction of coke nitrogen in the regenerator. 

Milford, J. B., A. G. Russell, and G. J. McRae, A New Approach to Photochemical Pollution Control Implications of Spatial Patterns in Pollutant Responses to Reductions in Nitrogen Oxides and Reactive Organic Gas Emissions, Environ. Sci. Technol., 23, 1290-1301 (1989). 

For the monocyclic complexes 1-7, oxidation to Ni(III) occurs at +0.90-+0.93 V and reduction to Ni(I) at -1.46--1.55 V vs SCE. However, in the macropolycyclic ligand complexes 9-14, oxidation and reduction occur at + 1.25-+1.60 V and at -0.94-—1.40 V vs SCE, respectively. That is, electrochemical oxidation of Ni(II) complex to Ni(III) species is easier for the monocyclic complexes, whereas electrochemical reduction to Ni(I) is easier for the macropolycyclic complexes. The anodic shifts in both oxidation and reduction potentials for Ni(II) macropolycyclic complexes in part may be attributed to the tertiary nitrogen donors of the ligands. 

Lead azide, like hydrazoic acid, is liable to undergo oxidation and reduction reactions. It is partially decomposed by atmospheric oxygen to form free hydrazoic acid, nitrogen and ammonia. This reaction is promoted by the presence of carbon dioxide in the air. When boiled in water, lead azide undergoes slow decomposition with the evolution of hydrazoic acid. 

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