Vehicle exhaust catalytic treatment

This paper describes the development and performance of a 16 mol% ceria stabilised zirconia supported palladium-zinc catalyst in vehicle exhaust after treatment. The main aspects of the novel catalytic system are i) the low temperature preparation of a thermally stable solid solution of tetragonal phase ceria stabilised zirconia, ii) the role of zinc in the dispersion of the palladium component and its synergetic interaction with palladium in an oxygen ion transfer mechanism, iii) the in situ perfomance of the catalyst under close-coupled engine conditions in producing... 

Catalytic treatment of motor vehicle exhaust has been applied in all passenger cars in the USA since the 1975 models. The first cars with electronic feedback systems and three-way catalysts were 1979 Volvos, sold in California. Today all new gasoline cars sold in the Western world are equipped with catalytic converters. It... 

In respect of the severe regulations imposed, the motor car manufacturers have decreased considerably the NOx emissions from their vehicles. Initially this was by a modification of the engine s combustion chamber. More recently these measures have proved less than sufficient and so to prevent pollution an exhaust after-treatment has become necessary. With this in mind, several technologies have been developed in order to decrease the harmful NOx emissions. One of which is selective catalytic reduction by hydrocarbons (HC-SCR). An enormous amount of catalytic materi tls have now been developed [1] and an appropriate choice would seem to be supported noble metal catalysts [2]. A high activity is generally observed at low temperature while the efficiency remains little affected by water. The effects ... 

Frequently exposed to very high temperatures, the catalysts used for depollution of motor vehicle exhaust gases are deactivated mainly by structural and textural evolution processes. This paper describes how the catalytic activity of a typical three-way catalyst (platinum-rhodium on a wash-coated cordierite monolith) was determined for the removal of hydrocarbons of various types before and after high-temperature treatments. Electron microscopy (CTEM and STEM) was used to determine metal particle size in fresh and aged catalysts. 

Furthermore, as clearly demonstrated by the three-way catalytic system for gasoline vehicles and DPNR explained in this chapter, the automobile exhaust gas treatment catalysts do not function alone, but rather require a highly controlled engine system. It is therefore necessary to further develop technologies to functionally integrate engine and after-treatment devices in which the soot oxidation catalyst is a component. 

Traditionally, monolith reactors have demonstrated their performance in gas-phase reactions, particularly in the treatment of automotive exhaust gases. Today, virtually all vehicles are equipped with catalytic converters. Here we will consider three-phase applications. These have been studied by a few authors and research groups such as Moulijn and coworkers [4,5] and Irandoust and Andersson [6]. Certain industrial processes such as hydrogenation of anthraquinone in the production of hydrogen peroxide are also examples of the monolith reactor technology being established on an industrial scale. Monolith... 

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