Conversion of nitrogen oxide

Nitrates those gases and aerosols that have origins in the gas-to-aerosol conversion of nitrogen oxides, e.g., NOj of primary interest are nitric acid and ammonium nitrate. Ammonium nitrate is very hygroscopic so its contribution to visibility impairment is magnified in the presence of water vapor. 

Laufs S, Burgeth G, Duttlinger W, Kurtenbach R, Maban M, Thomas C, Wiesen P, Kleffmann J (2010) Conversion of nitrogen oxides on commercial photocatalytic dispersion paints. Atmos Environ 44 2341-2349... 

Meijer E.W. and Velthoven P. (1997). The effect of the conversion of nitrogen oxides in aircraft exhaust plumes in global models. Geophys. Res. Lett., 24(23), 3013-3016. 

Table 1 Redox conversions of nitrogenous oxides during denitrification...

Use Lanthanum salts, electronic devices, pyrophoric alloys, rocket propellants, reducing agent catalyst for conversion of nitrogen oxides to nitrogen in exhaust gases (usually in combination with cobalt, lead, or other metals), phosphors in x-ray screens. 

Catalytic activity in the homogeneous gas-phase conversion of nitrogen oxides and carbon monoxide to nitrogen and carbon dioxide was observed to be most effective for the atomic ions Fe+, Os+, and Ir+ out of the investigation of 29 different transition metal cations M+ [462]. The overall catalytic scheme that was established in this study consists of the three catalytic cycles shown in Fig. 1.94. The catalysis occurs in two steps in which NO is first reduced to N2O. An analogous three-step catalytic reduction of NO2, in which NO2 is first reduced to NO, was also discovered. The three cycles in Fig. 1.94 were characterized with laboratory measurements of reactions of each of the three nitrogen oxides NO2, NO, and N2O with the different transition metal ions in an inductively coupled plasma/selected-ion flow tube tandem mass spectrometer [462]. 

Figure 113. Conversion of nitrogen oxides and gaseous hydrocarbons reached over different NO.v-reduction catalyst formulations, as a function of the exhaust gas temperature (monolith catalyst with 62 cells cm dedicated NO t-reduction catalyst formulations with zeolites and with different active components, after laboratory oven-aging in air at a temperature of 1023 K for 16 hours light-off test in a model gas reactor at a space velocity of 50000 N11 h model gas simulates the exhaust gas composition of an IDl/NA passenger car diesel engine at medium load and speed, except for the hydrocarbon concentration, which was increased to reach yHc yNO, 3 1 (mol mol)).

Figure 116. Conversion of nitrogen oxides reached over a NO. reduction catalyst at three different settings of the exhaust gas temperature, as a function of the concentration of the nitrogen oxides in the exhaust gas (light-off test in a model gas reactor at a space velocity of 50000 Ml T h". Model gas composition based upon the composition of the exhaust gas of an IDI/NA passenger car diesel engine at medium speed and load, but modified by adding -hexadecane to reach a hydrocarbon concentration of 3200 vol.ppm Ci and by varying the concentration of NO). Reprinted from ref. [72] with kind permission of Elsevier Science.

In the stratosphere, positive ions could contribute to the conversion of nitrogen oxides into nitric acid by the following chain ... 

The reaction rate was measured with respect to the conversion of nitrogen oxide to monoxide. The kinetics of the reaction were studied in the temperature range —15 to -l-5°C the rate constant in this temperature range varied from 0.066 to 0.25 mol sec . ... 

Figure 16.14 The inside of a catalytic converter is coated with particles of rhodium and platinum. At 500°C, rhodium catalyzes the conversion of nitrogen oxide (NO) to nitrogen (N2) and oxygen (O2). Platinum catalyzes the conversion of carbon monoxide (CO) to carbon dioxide (CO2) and converts any unburned gasoline, represented by CxHy, to carbon dioxide and water vapor (H2O). 

SNCR Selective noncatalytic conversion of nitrogen oxides by NH3 via gas-phase reactions. 

Conversion of nitrogen oxides in the presence of NH3 to yield N2 (selective catalytic reduction, SCR) Cu-ZSM-5, Cu-ZSM-ll,Cu-ZSM-12, Cu-P, Cu-SSZ-13, Cu-SAPO-34 Small-pore, highly hydrothermally stable zeolites are currently of increasing interest in the SCR process [58, 71]... 

K. (2003) Simultaneous conversion of nitrogen oxides and soot into nitrogen and carbon dioxide over iron containing oxide catalysts in diesel exhaust gas. Appl. Catal B Environ., 43 (3), 281-291. 

Kureti, S., Weisweiler, W. and Hizbullah, K. (2003). Simultaneous Conversion of Nitrogen Oxides and Soot into Nitrogen and Carbon Dioxide over Iron Containing Oxide Catalysts in Diesel Exhaust Gas, Appl. Catal. B Environmental, 43, pp. 281-291. 

In summary, SCR-NH3 is still the preferable process for the abatement of NO in stationary sources, but when N2O or combined N2O/NO abatement is the target of the process, hydrocarbons, and especially propane could be preferable. Still considerable improvement is required for the SCR-CH4 process, but developments in this field are very fast [22,23]. Better catalyst design based on understanding the relationship between nanostructure and reactivity is expected to improve performances of metal oxide catalysts in the conversion of nitrogen oxides [18]. 

The book starts with a detailed and fundamental structural characterization of the main ceria-based materials (Chapter 1), followed by a careful overview of recent achievements in ffR-TEM characterization (Chapter 2). Chapter 3 gives an insight into the oxygen storage and release capacity of both model and commercial ceria-containing three-way catalysts, which is one of the key properties in their successful application. A discussion of the role of ceria-based materials in the activation and conversion of nitrogen oxides (Chapter 4) closes the first part of the book. 

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