Catalytic destruction

Fig. 11-3. Stratospheric ozone and CIO concentrations at an altitude of 18 km measured by aircraft flying south over Antarctica on September 27,1987. The dramatic decrease in ozone at a latitude of 71 degrees is attributed to the role of CIO in catalytic destruction of ozone. Adapted from Anderson et al. (13).

Two-level diffuser contactors, which involve application of ozone-rich gas to the lower chamber. Lower chamber off-gases are applied to the upper chamber. Offgas treatment from contactors is an important consideration. Methods employed for off-gas treatment include dilution, destruction via granular activated carbon, thermal or catalytic destruction, and recycling. 

Stratospheric ozone production is balanced by various catalytic destruction sequences ... 

In order to calculate the steady-state concentration of ozone in the stratosphere, we need to balance the rate of production of odd oxygen with its rate of destruction. Chapman originally thought that the destruction was due to the reaction O + 03 —> 2O2, but we now know that this pathway is a minor sink compared to the catalytic destruction of 03 by the trace species OH, NO, and Cl. The former two of these are natural constituents of the atmosphere, formed primarily in the photodissociation of water or nitric oxide, respectively. The Cl atoms are produced as the result of manmade chlorofluorocarbons, which are photodissociated by sunlight in the stratosphere to produce free chlorine atoms. It was Rowland and Molina who proposed in 1974 that the reactions Cl + 03 —> CIO + O2 followed by CIO + O —> Cl + O2 could act to reduce the concentration of stratospheric ozone.10 The net result of ah of these catalytic reactions is 2O3 — 3O2. 

Fig. 3.9. Photochemical formation and non-catalytic destruction of ozone. UV-C radiation (200-280 nm wavelength) UV-B radiation (280-320 nm wavelength). Note how high-quality energy (UV radiation) is converted into lower quality energy (heat). Catalysts such as freons or nitrogen oxides can destroy ozone (e.g. Cl + 03 —> CIO + 02).

Mudge, L. K. Baker, E. G. Brown, M. Wilcox, W., Catalytic destruction of tars in biomass-derived gases. In Research in Thermochemical Biomass Conversion, Bridgwater, A. V. Kuester, J. L., Eds., Elsevier Applied Science, London, 1988, pp. 1141-1155. 

Catalytic destruction. Catalytic conversion of hypochlorite to chloride and oxygen can be facilitated by nickel. With the Hydecat process, ICI has a commercial solution available. 

Abbott, P.E.J., Carlin, M., Fakley, M.E., Hancock, F.E. King, F. (1991) ICIHYDECAT process for the catalytic destruction of hypochlorite effluent streams. In Modern Chlor-Alkali Technology (ed. T.C. Wellington), Vol. 5, pp. 23-34. Published for SCI by Elsevier Science, Amsterdam. 

These reactions emphasize the importance of solar radiation in NO/NO2 catalytic destruction cycle of ozone. One can immediately see that to provide any reliable observational basis for importance of NO/NO2 in ozone balance, we must have not only NO/NO2 concentration but also its diurnal variation which provides proper check on the time constants for the reactions described in Eqs. (7)-(9). 

Recent discussions of stratospheric chemistry have dealt with the effect of freons on ozone balance through a Cl/ClO catalytic destruction of ozone. The fundamental absorption band of CIO is measured to be at 11 /xm. Isotopically substituted CO2 laser based OA absorption measurement technique should allow us to carry out fundamental measurements on CIO and its diurnal variation in the stratosphere to provide yet another important parameter (in addition to NO above) in the stratospheric ozone chemistry. 

The loss of 03 at latitudes where CIO has a high concentration is consistent with the known chemistry of catalytic destruction of 03 by halogen radicals. [Prom J. G. Anderson, W. H. Prune, and M. H. Proffitt, J. Geophys. Res. 1989, 94D, 11465.]... 

What role do chlorofluorocarbons play in the catalytic destruction of ozone ... 

CA 45, 2885(195lXHydrogenati°n of nitrocompds with Raney Ni treated with chloroplatinic acid and with alkali) p)J.A.Grand R.Miller, USP 2555333(1951) CA 45, 7337(1951XUse of Cu chromite as combustion catalyst in solid compressed fuel, such as mixt of NGu 75 GuN 25%) r)Anon, ChemEngrg 1951, June, p 183 (Catalytic process for waste disposal developed by D.V.Moses and put into operation at DuPont s Belle Plant, West Virginia, consists of vapor -phase catalytic destruction of organic wastes by oxidation to C02 H20. It was claimed that the method is more convenient than bio-oxidation... 

Catalytic Destruction There are several different mechanisms of ozone destruction that predominate... 

G. R. Lester, "Catalytic Destruction of Hazardous Halogenated Organic Chemicals," presented at the 8 2nd Annual AWMA Meeting Exhibition,... 

Pichat P, Guillard C, Maillard C, Amalric L, D Oliveira JC. Ti02 photo-catalytic destruction of water aromatic pollutants intermediates properties-degradability correlation effects of inorganic ions and Ti02 surface area comparisons with H202 processes. In Ollis DF, Al-Ekabi H, eds. Photo-catalytic Purification and Treatment of Water and Air. Amsterdam Elsevier, 1993 207-223. 

Monsanto Enviro-Chem offers NOx abatement technology that is licensed from Rhodia of France. It includes a High Efficiency Absorption (HEA) section for extended absorption and a catalytic reduction section (SCR) for Catalytic Destruction ofNOx (i.e., the DCN technology)99. 

The atmospheric chemistry of the organobromides is similar to that of the organochlo-rides degradation ultimately produces bromine atoms which may participate in catalytic destruction of ozone through a BrOx catalytic cycle (reactions 12 and 13). 

These include the control of particulate emissions, adsorption of PCDD/Fs by activated carbon or other substrates, and decomposition of PCDD/Fs or catalytic destruction. 

Catalytic Destruction. It has been reported that catalysts employed for the selective catalytic reduction (SCR) of NOx emissions also demonstrate the ability to decompose organohalogen compounds, including PCDD/Fs.39 Successful pilot trials at MSW and hazardous waste incineration facilities indicated that PCDD/F emission concentrations of <0.1 ng I-TEQ m 3 could be achieved in the absence of ammonia when titanium dioxide-based SCR catalysts were maintained between 200-350°C. 

V. S. Smentkowski, P. L. Hagans, and J. T. Yates (1988) Study of the catalytic destruction of dimethyl methylphosphonate(DMMP) oxidation over molybdenum) 110), J. Phys. Chem 92 6351-6357... 

Stratospheric ozone Emission of ozone-depleting compounds (CFCs, Halons) Chemical reaction release of C1 and Br in stratosphere Catalytic destruction of ozone in stratosphere Skin and crop damage, damage to materials Ozone Depletion Potential (ODP)... 

Similar chain reactions can be written for reactions involving R02- In contrast, when relatively little NO is present, as in the remote atmosphere, the following cycle can dominate over ozone production leading to the catalytic destruction of ozone, viz ... 

Potentially, the most important effect of reactive halogen species maybe that their chemistry may lead to the catalytic destruction of ozone via two distinct cycles Cycle I ... 

These reactions constitute a source of OH in upper stratosphere, which ultimately controls the upper boundary of the ozone layer through the OH/HO2 catalytic destruction cycles [5] getting rid of about 10% of the existing ozone [6]. The decrease of the ozone layer is a well known problem, see e,g, [3,7-9]. 

Weckhuysen et al. found the destruction of carbon tetrachloride (CCI4) on Ce02 or La203 in the presence of oxidants. In the process, the rare earth oxides are chlorinated (Weckhuysen et al., 1999). Later they reported the catalytic destruction of CCI4 over a series of lanthanide and alkaline-earth metal oxides based catalysts in the presence of water steam (Van der Avert et al., 2004). The catalysts combined the destruction on basic oxide surface and concurrent dechlorination of the partially chlorinated solid by steam. The two noncatalytic reactions combined into a catalytic cycle in this way. 

Definitely yes. In the troposphere, to which I think you may be referring, N2O is relatively inert. It is in the stratosphere where reaction (18) plays such an important role releasing the nitrogen oxides which dominate the catalytic destruction of ozone. 

We close this section by summarizing the chemistry of chlorine and ozone in the Earth s stratosphere. There are three essential elements in the Rowland-Molina mechanism linking the release of fluorocarbons to the gas phase catalytic destruction of ozone in the stratosphere ... 

Chintawar, P. S. Greene, H. L. Adsorption and Catalytic Destruction of Trichloroethylene in Hydrophobic Zeolites. Appl CatB. 14 (1997) pp. 37-47. 

Stoll M Furrer J., Seifert H. (2000) Catalytic Destruction of Chlorinated Aromatic Compounds with a V-Oxidc Catalyst Proceed, of ITS Conference on Incineration held in Portland, OR, USA. 

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