Heterogeneous catalysis, troposphere

HETEROGENEOUS CATALYSIS IN THE TROPOSPHERE A POSSIBLE IMPACT ON THE GLOBAL CHEMISTRY OF THE ATMOSPHERE... 

Heterogeneous catalysis has a role in the atmospheric chemistry of ozone in the troposphere as well. Catalytic converters in automobiles are filled with a porous ceramic material, which provides a surface that catalyzes the removal of CO and NO (nitrogen oxides) ftom the exhaust. (Nitrogen oxides initiate the formation of ozone and other lung irritants in photochemical smog. We will examine this process in detail in Section 11.8.) The process by which catalytic converters operate is shown in Figure 11.14. The types of steps shown there are found in most examples of heterogeneous catalysis. 

At present it is not possible to suggest more precise estimates than those made in this article, of the actual role of particular photocatalytic reactions in the atmosphere. To improve present knowledge, it is necessary to study in laboratories the quantitative characteristics of heterogeneous photocatalysis and thermal catalysis over natural aerosols, and under conditions that would be more close to those in the atmosphere. The most important characteristic to be measured is the quantum yield of photocatalytic reactions of atmospheric components on atmospheric aerosols containing Fe203, Ti02, and ZnO, since these are the most plausible candidates for the role of photocatalysts due to their appropriate photochemical properties and rather high concentration in the troposphere. 

Litter, M. I. (1999) Heterogeneous photocatalysis - transition metal ions in photocatal)rtic systems. Applied Catalysis B Environmental 23, 89-114 Liu, X., G. Mauersberger and D. MoUer (1997) The effects of cloud processes on the tropospheric photochemistry an improvement of the EURAD model with a coupled gaseous and aqueous chemical mechanism. Atmospheric Environment 19, 3119-3135 Livingstone, D. A. (1963) Chemical composition of rivers and lakes. In U.S. Geological Survey Professional Paper, 6 ed. (Ed. M. Fleischer), pp. 1 -64 Lloyd, G. E. R. (1970) Early Greek science Thales to Aristotle. W. W. Norton Co., New York, 156 pp. 

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