Metal Oxide Materials for Automotive Catalysts
Nanostructured metals and metal oxides are combined to produce advanced automobile catalysts for exhaust pollutant control. Catalytic emissions control was introduced in the form of noble metal-based three catalysts for the removal of exhaust gas pollutan
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Metal Oxide Materials for Automotive Catalysts Masakuni Ozawa
Abstract Nanostructured metals and metal oxides are combined to produce advanced automobile catalysts for exhaust pollutant control. Catalytic emissions control was introduced in the form of noble metal-based three catalysts for the removal of exhaust gas pollutants of hydrocarbons (HC), carbon monoxide, and nitrogen oxides (NOx). Alumina as wash coat components provides a high and stable surface area for dispersion of the precious metals. Cerium oxides (ceria, CeO2) and ceria-zirconia (CeO2–ZrO2) as oxygen storage capacity components are typical non-metallic functional materials in the automotive catalysts. The catalysts component layer is some hundreds of micrometers thick and loaded on the substrate, usually made from cordierite ceramic and metallic alloys, which is called coat layer with alumina-based and precious metal and ceria-based ceramic composite. This section deals with developed metal oxide materials controlled with nanometer scale, their structures, and some current advances including the author’s achievement.
Keywords Three-way catalyst (TWC) Noble metals Nanoparticle Oxygen storage capacity
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Al2O3 CeO2 ZrO2
Catalysts and Metal Oxide Nanomaterials
Automotive catalysts for the exhaust depollution were first applied to US and Japan vehicles manufacture industry in 1975 [1–6]. They are the principal emission control tools and typical model as an application of environmental materials to devices, proving their usefulness on environmental improvement. The environmentally functional materials have made catalytic devices which contain practical nanomaterials, and the catalytic methods for exhaust gas treatment have established M. Ozawa (&) Materials Division, Institute of Materials and Systems for Sustainability, Nagoya University, Nagoya 464-8603, Japan e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2019 Y. Setsuhara et al. (eds.), Novel Structured Metallic and Inorganic Materials, https://doi.org/10.1007/978-981-13-7611-5_24
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now and most of the automobiles have equipped the catalysts for emission control. Thus, these environmental materials have both large industrial market and requirement of improvement for pollution control around citizen life. Figure 24.1 shows an example of a catalyst converter part which is usually both attached near engine exhaust manifold and underbody in a car. When a driver first starts the automobile both the engine and the catalyst are cold, and it reaches a temperature high enough to initiate the catalytic reactions after the exhaust gradually warms. This is referred to as the light-off performance of catalyst and it depends on the nanomaterials combination of catalyst and its chemistry since all the transport reactions must be fast and complete. The three-way catalysts (TWCs) in gasoline engine are the most widely used and effective system for the exhaust gas pollutants including hydrocarbons (HC), carbon monoxide, and nitrogen oxides (NOx). The c
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