Atmospheric ozone depletion

Production of hydrogen fluoride from reaction of Cap2 with sulfuric acid is the largest user of fluorspar and accounts for approximately 60—65% of total U.S. consumption. The principal uses of hydrogen fluoride are ia the manufacture of aluminum fluoride and synthetic cryoHte for the Hall aluminum process and fluoropolymers and chlorofluorocarbons that are used as refrigerants, solvents, aerosols (qv), and ia plastics. Because of the concern that chlorofluorocarbons cause upper atmosphere ozone depletion, these compounds are being replaced by hydrochlorofluorocarbons and hydrofluorocarbons. 

Abstract Heterogeneous chemical reactions at the surface of ice and other stratospheric aerosols are now appreciated to play a critical role in atmospheric ozone depletion. A brief summary of our theoretical work on the reaction of chlorine nitrate and hydrogen chloride on ice is given to highlight the characteristics of such heterogeneous mechanisms and to emphasize the special challenges involved in the realistic theoretical treatment of such reactions. 

The discovery of the Ozone Hole in the Antarctic stratosphere has led to the realization that previously unsuspected heterogeneous chemical reactions occuring on the surface of ice and other stratospheric cloud particles play a critical role in atmospheric ozone depletion — not only in the Antarctic stratosphere,... 

However, trichlorofluoromethane is an atmospheric ozone depletion chemical, and therefore, alternatives have been under investigation. There have been many other agents used for flash spinning PE to either minimize or eliminate the potential for ozone depletion. 

Chlorinated alkanes were used in the production of chlorofluoroalkanes (CFCs).188 Because of their atmospheric ozone-depleting ability, the use of CFCs is being phased out. Hydrochlorofluorocarbons, containing at least one hydrogen atom (HCFCs), are introduced as safer alternatives.189 190 In the long run, however, hydrofluorocarbons (HFCs) will be the ideal substitutes to CFCs.190... 

Many people hear about atmospheric ozone depletion and wonder why we don t simply replace that which has been destroyed. Knowing about chlorofluorocarbons and knowing how catalysts work, explain how this would not be a lasting solution. 

Propellants are generally high-vapor-pressure CFCs and HFAs. Until recently the most common examples were the CFC propellants 11, 12, and 114. These propellants have been superceded in new formulations by HFA 134a and 227. The HFA propellants are intended to replace CFC 12. Some of the physicochemical characteristics of these propellants are shown in Table 1. The use of atmospheric-ozone-depleting CFCs in inhalers was a hotly debated issue in the late 1980s and early 1990s [11,12]. This may be followed in the professional literature [13-23]. It is now clear that CFCs will... 

Except for atmospheric ozone depletion potential of perfluorinated compounds. Except for corrosive effects and potential toxicity. 

In the early 1990 s it was reported that N2O emissions from adipic acid producers could contribute to atmospheric ozone depletion and global warming [I]. It was estimated that adipic acid production may account for up to 10% of the annual increase in the atmospheric N2O. Ihls report sparked an abatement initiative among the major adipic acid producers. Successes have been announced and implementations are scheduled for 1996-98 [2]. However, Monsanto was already practicing complete abatement by a thermal reduction process and elected to pursue a more desirable path of value-added utilization. 

Although atmospheric ozone depletion is a widely known phenomenon, the estimate that as much as 90% of the xenon originally in Earth s atmosphere is now absent is largely unknown. The synthesis and study of Xe02 (D. S. Brock, G. J. Schrobilgen, J. Am. Chem. Soc., 2011, 133, 6265) supports the hypothesis that the reaction of Si02 from the Earth s core with Xe may be responsible for the depletion of this noble gas. 

Chlorofluorocarbons have been used as refrigerants for the past 50 years, but their use is now being phased out worldwide because of concerns about atmospheric ozone depletion. Draw the Lewis structure of dichlorodifluoromethane, CF2CI2, also known as DuPont s Freon-12. 

THEORETICAL STUDIES OF HETEROGENEOUS REACTIONS IMPORTANT IN ATMOSPHERIC OZONE DEPLETION... 

Significant atmospheric ozone depletion is not restricted just to the Antarctic stratosphere. In addition to other locations in the atmosphere [1], there is significant ozone depletion in the springtime Arctic tropospheric boundary layer, where bromine is much more abimdant than elsewhere, and where heterogeneous bromine chemistry is implicated in extremely rapid ozone depletion near ground level [25-27]. 

Theoretical studies of heterogeneous reactions important in atmospheric ozone depletion 379... 

Q.-B. Lu, Phys. Rep., 487,141-167 (2010). Cosmic-Ray-Driven Electron-Induced Reactions of Halogenated Molecules Adsorbed on Ice Surfaces Implications for Atmospheric Ozone Depletion and Global Climate Change. 

Fig. 5.3 Atmospheric ozone depletion (%) on August 1 of the same year as the Scenario II nuclear war. Negative values indicate ozone increases and show the opposite effects of NOx injections on ozone in the upper and lower regions of the atmosphere...

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