NO2, oxidation

Oxidation of SO2 is slow in a mixture of pure gases, but the rate is increased by light, NO2, oxidants, and metallic oxides which act as catalysts for the reaction. The formed acids can react with particulate matter or ammonia to form salts. 

B.A. Williams and J.W. Fleming. Comparison of Species Profiles between O2 and NO2 Oxidizers. Combust. Flame, 100 571-590,1995. 

Calvert, J. G. Stockwell, W. R. Mechanism and rates of the gas-phase oxidations of sulfur dioxide and nitrogen oxides in the atmosphere. In S02> NO and NO2 Oxidation Mechanisms Atmospheric Considerations Calvert, J. G., Ed. Butterworth Boston, 1984 pp. 1-62. 

The other version of oxidative phosphorylation used by autotrophs involves the release of electrons from an inorganic energy source. An example of this is the release of electrons from NH4, oxidizing NH4 to NO2, and the release of electrons from NO2, oxidizing NO2 to NO3. 

NO2 oxidation NO2 oxidizers (e.g., Nitrobactef) Aerob Chemo-autotrophic Source of energy 5... 

Schwartz, S. E. (1984) Gas-Aqueous Reactions of Sulfur and Nitrogen Oxides in Liquid Water Clouds. In SO2, NO and NO2 Oxidation Mechanisms, J. G. Calvert, Ed., Butterworth, Boston. 

The influence of NO on electric contact materials seems often to be due to synergistic effects with other pollutants. Whereas exposure of e.g. copper and gold contacts in an atmosphere of NO shows no corrosion effect the synergistic effect of SO and NO2 is very pronounced (, ). A possible explanation is that NO2 oxidizes SO2 to sulfuric acid according to the following reaction ... 

The reaction of NO, NO2, and NH3 over a CuO/NiO on (X-Al203 catalyst was studied by Blanco et al. [114]. Ammonia chemisorbs on the catalyst surface forming NH2 species, whereas copper is reduced to Cu+. Evidence for the presence of Cu+ was obtained by means of XPS and FTIR. Then NO2 oxidizes Cu into Cu + to form NO. This adsorbed NO reacts with the NH2 species through a Langmuir-Hinshelwood mechanism. NO present in the gas phase can react with the catalyst through an Eley-Rideal mechanism forming a reduced copper site. The Cu+ sites are promptly reoxidized by O2 or NO2 O2 plays a minor role in the reoxidation. 

Nitric acid is a powerful oxidizing agent. The oxidation number of N in HNO3 is -1-5. The most common reduction products of nitric acid are NO2 (oxidation number of N = -1-4), NO (oxidation number of N = -1-2), and NH4 (oxidation number of N = -3). Nitric acid can oxidize metals both below and above hydrogen in the activity series (see Figure 4.15). For example, copper is oxidized by concentrated nitric acid, as discussed earlier. 

Hoffmann, M. R., and Jacob, D. J. (1984) Kinetics and mechanisms of the catalytic oxidation of dissolved sulfur dioxide in aqueous solution an application to nighttime fog water chemistry, in 50, NO, and NO2 Oxidation Mechanisms Atmospheric Considerations, edited by J. G. Calvert. Butterworth, Stoneham, MA, pp. 63-100. 

For longer chain alkanes ( 04) the reaction mechanism becomes more complex due to the IsomerIzatIons of the alkoxy radicals (47, 48), and to the fact that addition of NO to the alkyl-peroxy radicals (49) becomes more Important than NO to NO2 oxidation. For the alkenes and aromatic hydrocarbons the oxidation mechanisms In the atmosphere are more complex, and discussions of these systems, along with a more detailed treatment of the alkanes, are given later. 

In contrast to the energetic arguments discussed earlier, superb performance in environmentally relevant photocatalysis (liquid-phase oxidation of phenol and gas-phase NO2 oxidation) has been recently demonstrated by catalysts containing ultrasmall, sub-1 nm gold clusters [197]. Authors reported a remarkable improvement (by a factor of 6) in NO2 conversion when Ti02 was modified with Au clusters. Catalysts were prepared by synthesizing ultrasmall, monodisperse gold clusters... 

The fractions of the 1-ethoxyethoxy radicals undergoing reactions 1-4 are shown in Tables and compared with previous FllR studies and with theoretical estimates. Although diethyl ether is rapidly photo-oxidised, its contribution to tropospheric ozone formation is limited as one of the major products is ethyl formate which is relatively unreactive in the troposphere. This is also confirmed from the NO-NO2 oxidation stoichiometry, ca, 1 mole NO is oxidised per mole diethyl ether reacted. 

Continuous Regenerable Trap. Another approach is to generate NO2 upstream of an uncatalyzed DPF for combusting the particulate matter. This so-called continuous regenerable trap (or CRT) is based on phenomenon first published in 1989 by Cooper and Thoss (143), in which NO2 oxidized the dry carbon soot held within the trap at temperatures below that of similar oxidation with the O2 in the air. This technology is considered passive in contrast to this active system. 

Oxidized paraffin soaps can be synthesized by adopting petroleum paraffin as raw material. Because synthetic reaction of oxidized paraffin is relatively simple, oxidized paraffins are widely applied in industry. Synthetic methods of oxidized paraffin comprise air oxidation process and NO2 oxidation process. Air oxidation process is widely applied. In general, petroleum paraffin is heated to 150 or above in the presence of O2 and KMn04. The oxidation reactions can be given by ffie following ... 

Figure 4.10 Representation of ketene and epoxide formation from NO2 oxidation of (10,0) carbon nanotube. Reproduced from Ref. 27 with permission through ACS Author-Choice/Editors Choice.

Several literature reports confirm, in fact, that zeolite catalysts are able to adsorb NO2 in the form of nitrates. NO2 chemisorption can be described by the following two-step mechanism, schematically representing disproportionation and heterolytic chemisorption of NO2 to form surface nitrites and nitrates, step (9.1), followed by NO2 oxidizing the nitrites to nitrates, step (9.2) ... 

In zeolite-based catalysts, the N02/NO c ratio is known to have a significant effect on the de-NO c performance [34, 35]. The ability of the catalyst to modify the NO2/ NO t ratio in situ has to be considered by the NO NO2 oxidation/decomposition reaction ... 

Jing et al. [97] and Rodes et al. [107] observed an NO2 oxidation peak on a CV scanning curve. This indicated that NO could adsorb on the Ft surface and affect the ORR. The observation of increased kinetic resistance in the ORR after exposure to NO [108] provided further support for this mechanism. 

NO2 Oxides of nitrogen include both NO and NO2. Emission limits are generally based on parts per million by volume (ppmv) of the total of NO and NO2 emitted by combustion... 

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