University of Tehran

Synthesis, activity and thermal stability of gold nanoparticle on modified nh4-y type zeolite for cooxidation

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Carbon monoxide (CO) is a gaseous pollutant which enters the atmosphere from four major sources: fossil fuel combustion and industrial emissions, biomass burning, oxidation of CH4, and oxidation of hydrocarbons. The presence of CO causes problems to human health, particularly in cases of locally high concentrations, and affects the oxidizing capacity of the troposphere. Automobile emissions are the major urban source of carbon monoxide, and they are also important globally. One estimate by the Japanese Automobile Research Institute (JARI) of the 1990 global CO emissions from automobiles is 231 megatonnes (Mt). The same source gives the USA 1990 emissions as 21Mt, whereas the US Environmental Protection Agency (EPA) estimate 57Mt (Bradley et al., 1999). The three major pollutants emitted by internal combustion engines are carbon monoxide, unburned hydrocarbons and nitrogen oxides. Catalysts that are capable of removing these pollutants simultaneously are generally referred to as threeway catalysts (TWCs) and the design of these catalyst systems is continually evolving to meet lower emission requirements (Mellor et al., 2002). A new catalyst that has been introduced recently for oxidation of CO is gold nanoparticl. The application of gold catalysts to the oxidation of carbon monoxide has been studied extensively, most notably by Haruta et al., 1993. A significant feature of gold-based catalysts is the low temperature oxidation of carbon monoxide, where the catalysts display activity at temperatures as low as -70ºC (Mellor et al., 2002).

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