EURO-ECO 2011 Hanover 21 - 22 November 2011	Environmental, Engineering - Economic and Legal Aspects for Sustainable Living
	European Academy of Natural Sciences, Hanover European Scientific Society, Hanover University of Bremen, Bremen

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Increasing number of vehicles equipped with gasoline and diesel engines may now be responsible for more than 60% of total atmosphere pollution in large cities. An effective abatement of main constituents of automobile exhaust gases, such as NO_x, CO and hydrocarbons, today is considered to be one of the most important ecologic issue.

Catalytic on-board neutralization system (convertor) is already used widely in many countries to reduce the level of toxic compounds released with exhaust gases. It consists of metal or ceramic substrate with supported washcoat - layered active component. Typically washcoat comprises metal oxides serving as support for dispersed particles of noble metals (Pd, Pt, Rh).

During the working cycle automotive convertors are exposed to rather high temperatures and sudden temperature oscillations which may lead to quick deactivation of catalyst. At temperature of 900°C and above the alumina surface area drops down, and the sintering of noble metal particles occurs, too. Both processes result in catalytic activity decline. Dispersed Pd particles readily undergo sintering into agglomerates; rhodium gets oxidized from Rh⁰ to Rh³⁺ state followed by diffusion of the Rh³⁺ ions into the support bulk.

Bimetallic Pd-Rh and Pt-Rh systems are known to be more stable and catalytically active than the corresponding monometallic catalysts. In this work, bimetallic Pd-Rh alloy particles were synthesized by deposition on support. The catalyst containing Pd_xRh_1-x (x=0.5, 0.6) solid solution as an active component was shown to be both thermally and chemically stable under redox conditions. It has been elucidated that the formation of Pd-Rh alloy particles on the catalyst surface prevents Rh diffusion into the bulk of support. In addition, Pd-Rh alloy species are more stable towards aggregation and sintering. The results presented in this work also suggest that catalytic performance of the resulted catalyst strongly depends on preparation procedure.

This study was carried out in the framework of Scientific Educational Centre “Catalysis” between Boreskov Institute of catalysis SB RAS, Novosibirsk State University and Novosibirsk State Technical University.