Aspects of Automotive Catalyst Preparation, Performance and Durability

Cooper, Barry; Evans, W.D.J.; Harrison, Brian

doi:10.1016/s0167-2991(09)60417-1

Cited by 21 publications

(5 citation statements)

References 29 publications

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“…The Pd/CeO 2 catalyst was prepared through incipient wetness impregnation, which is often used to synthesize conventional, surface-impregnated catalysts. 46,47 The Pd/CeO 2 catalyst is made up of 2 to 5 nm Pd nanoparticles distributed along the surface of CeO 2 nanospheres. Similar to the Pd@ CeO 2 shell, the CeO 2 nanospheres are made up of numerous, packed crystallites that form a structure on the order of 50 nm in diameter.…”

Section: Resultsmentioning

confidence: 99%

Thermally Induced Restructuring of Pd@CeO₂ and Pd@SiO₂ Nanoparticles as a Strategy for Enhancing Low-Temperature Catalytic Activity

et al. 2019

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Retaining high catalytic activity after exposure to elevated temperatures remains a crucial challenge for applications such as automotive emissions control. While catalysts generally sinter and lose activity after aging at high temperature, here we illustrate that palladium in a core@shell morphology responds very differently. After 800 °C aging in oxygen, palladium redisperses into the encapsulating shell. The redispersion is more pronounced, and nearly complete, when palladium is encapsulated by reducible ceria, as opposed to nonreducible silica. This difference is likely due to the availability of lattice oxygen. Through comparisons with polycrystalline ceria nanoparticles, surface decorated with Pd, we show that for favorable restructuring to occur under our simple aging conditions, the process must start from a particular initial configuration, the

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Section: Resultsmentioning

confidence: 99%

Thermally Induced Restructuring of Pd@CeO₂ and Pd@SiO₂ Nanoparticles as a Strategy for Enhancing Low-Temperature Catalytic Activity

et al. 2019

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“…The A BET and C Winf values in Table 4 are based on the substrate washcoat loading. The initial diameter D 0 of the catalyst particle is 0.5 nm; this value is based on values from the literature (see, for example, reference [10]). It represents a metal particle with a diameter equivalent to about two atomic diameters.…”

Section: Combined Poisoning and Sintering Modelmentioning

confidence: 99%

Phosphorus deposition on a three-way catalyst under accelerated ageing conditions

Benjamin

Brogan

Collin³

et al. 2011

Proceedings of the Institution of Mechanical Engineers, Part D:

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Degradation of catalyst performance with time is described as ageing. There are two significant ageing mechanisms: poisoning and sintering. Experimental data on ageing have been obtained on an engine test bed using a specially designed catalyst core holder; the catalyst samples were subjected to different accelerated ageing regimes and durations. The ageing regimes were as follows: low temperature dosed (mainly poisoning); high temperature not dosed (mainly sintering); high temperature dosed (both sintering and poisoning). The experiments provided a series of samples from which the spatial and time dependences of the poisoning have been found. Portions of the samples were subjected to X-ray fluorescence analysis after ageing. A combined model of poisoning and sintering was developed and incorporated into a computational fluid dynamics model. This combined model can predict the level of deactivation as a function of length along the catalyst and as a function of time. Agreement between measured poison accumulation and predictions was achieved by tuning the sintering parameter.

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“…Often, the air/fuel ratio moved randomly either side of the stoichiometric point, and it was observed that a platinum/rhodium catalyst could, under appropriate conditions, simultaneously convert CO and HC (oxidations) and reduce NO x with high efficiency. 42 This catalyst concept became known as a three-way catalyst (TWC), because all three pollutants are removed from the exhaust gas simultaneously. Application of the TWC required three elements: (i) Electronic fuel injection (EFI) so precise amounts of fuel could be metered to provide a stoichiometric air/fuel mixture.…”

Section: Three-way Catalysts (Twcs) From Carsmentioning

confidence: 99%

Development of platinum catalysts and their use in the control of vehicle exhaust emissions

Twigg¹

2005

Applied Earth Science

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Metallic platinum is an excellent catalyst for a range of reaction types, and has a long history associated with the early development of catalysis. When it was necessary to have additional exhaust emissions control for cars, platinum-based oxidation catalysts were used to remove hydrocarbon and carbon monoxide. Later, nitrogen oxides were also removed in a two-stage process involving a platinum/rhodium catalyst followed by a platinum-based oxidation catalyst. When exhaust gas composition could be kept stoichiometric, hydrocarbons, carbon monoxide and nitrogen oxides were simultaneously converted over a single platinum/rhodium three-way catalyst. Modern three-way catalysts contain combinations of these metals, and emissions are exceptionally low. Nitric oxide is not catalytically dissociated under lean conditions, and its control from lean-burn gasoline engines involves forming nitrate that is stored and periodically reduced to nitrogen by enrichment of the exhaust gas. This method is being modified for diesel engines, and a platinum component has the key role of oxidising nitric oxide to nitrogen dioxide, the nitrate precursor. Diesel engines produce soot, and filtration is being introduced to remove it. The exhaust temperature of heavy-duty diesels is high enough (250-400°C) for nitric oxide to be converted to nitrogen dioxide over an upstream platinum catalyst, and this smoothly oxidises retained soot in the filter. The temperature of passenger car diesels is too low for this to take place all the time so trapped soot is periodically burnt in oxygen above 550°C. Here, a platinum catalyst is used to oxidise higher than normal amounts of hydrocarbon and carbon monoxide upstream of the filter to give sufficient temperature for soot combustion to take place.

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Aspects of Automotive Catalyst Preparation, Performance and Durability

Cited by 21 publications

References 29 publications

Thermally Induced Restructuring of Pd@CeO₂ and Pd@SiO₂ Nanoparticles as a Strategy for Enhancing Low-Temperature Catalytic Activity

Thermally Induced Restructuring of Pd@CeO₂ and Pd@SiO₂ Nanoparticles as a Strategy for Enhancing Low-Temperature Catalytic Activity

Phosphorus deposition on a three-way catalyst under accelerated ageing conditions

Development of platinum catalysts and their use in the control of vehicle exhaust emissions

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Aspects of Automotive Catalyst Preparation, Performance and Durability

Cited by 21 publications

References 29 publications

Thermally Induced Restructuring of Pd@CeO2 and Pd@SiO2 Nanoparticles as a Strategy for Enhancing Low-Temperature Catalytic Activity

Thermally Induced Restructuring of Pd@CeO2 and Pd@SiO2 Nanoparticles as a Strategy for Enhancing Low-Temperature Catalytic Activity

Phosphorus deposition on a three-way catalyst under accelerated ageing conditions

Development of platinum catalysts and their use in the control of vehicle exhaust emissions

Contact Info

Product

Resources

About

Thermally Induced Restructuring of Pd@CeO₂ and Pd@SiO₂ Nanoparticles as a Strategy for Enhancing Low-Temperature Catalytic Activity

Thermally Induced Restructuring of Pd@CeO₂ and Pd@SiO₂ Nanoparticles as a Strategy for Enhancing Low-Temperature Catalytic Activity