III International Conference

PP-III-47MIGRATION OF SUPPORTED PLATINUM METALS IN CATALYSTS FORAUTOMOTIVE EXHAUST PURIFICATIONPorsin A.V., Denisov S.P., Danchenko N.M., Alikin E.A.,Smirnov M.Yu. 1 , Bukhtiyarov V.I. 1 Bol’shakov A.M. 2Ural Electrochemical Integrated Plant, "department 47", Novouralsk, Russia1 Boreskov Institute of Catalysis SB RAS, Novosibirsk, Russia2 N.S. Kurnakov Institute of General and Inorganic Chemistry RAS, Moscow, RussiaE-mail: uvm88@ueip.ruAgeing of a Pt-Rh catalyst for automotive exhaust purification causes migration of Pt andRh for a distance of several microns. The migration results in the formation of Pt-Rh alloyfrom Pt and Rh particles separated from each other in the initial catalyst. Moreover, raisingthe temperature and time of the catalyst ageing leads to the transport of platinum metals fromAl 2 O 3 to CeO 2 that is accompanies by significant increase in dispersion of supported alloyparticles.More than one platinum metal (typically, platinum and rhodium) are often introduced intoautomotive exhaust purification catalysts in order to improve their performance. To avoidalloying of platinum and rhodium that might affect negatively on the performance of theautomotive catalysts, metals are deposited on a substrate in separate layers.Such a two-layer Pt-Rh catalyst (B08/40) designed and produced by Ural ElectrochemicalIntegrated Plant, was studied by TEM, XPS, XRD and BET methods after ageing at differentconditions. The inner layer of the catalyst in its initial state attached directly to a cordieritesubstrate consists of a mixture of CeO 2 and Pt supported on γ-Al 2 O 3 . The outer layer containsRh supported on γ-Al 2 O 3 . Such distribution of the components given by a preparationprocedure guarantees the separation of Rh particles from Pt and CeO 2 by distance of aboutseveral tens of microns. Before physical-chemical characterization, samples of the B08/40catalyst were aged:- in a motor testing bench for 4, 10 or 20 hours at reaction gas temperature of1000 ± 50°C;- in a motor vehicle during the run of 120000 km;- in hydrothermal conditions (HTC) at 980 °C.A washcoat layer containing active components of the catalyst was detached from thesubstrate after ageing procedures and was then studied with physical-chemical methodsmentioned above.557