Kinetic Measurements of Catalytic Converter Reactions by Using Modern Surface Sensitive Techniques

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ABSTRACT CTS-9525761 This project employs a molecular approach to characterize the kinetic details of catalytic processes relevant to the functioning of automotive catalytic converters for environmental control. Modern ultrahigh-vacuum techniques are used in conjunction with atmospheric-pressure catalytic reactors. The oxidation of carbon monoxide on platinum and the reduction of nitric oxide (by carbon monoxide or oxygen) on rhodium are studied by measuring sticking coefficients and reaction rates using the method of King and Wells in which the partial pressures of the gases are recorded with a mass spectrometer while a collimated gas beam impinges directly on the surface. The experiments emulate competitive adsorption either by exposing the substrate to a mixture of gas species or by preadsorbing one species before exposure to another. Gaseous species studied are those in combustion exhaust, including water and carbon dioxide. Experimental results are modeled using a Monte Carlo computer simulator algorithm. The oxidation of methane over palladium is also studied. This study is based on experimental models for the catalytic systems used in automotive exhaust control. However, it is also relevant to pollution control of emissions from other (stationary) combustion systems including power plants, heating systems, incinerators, and steam plants.