Supported bimetallic catalysts thermal treatment

The now classical methods used for the preparation of supported gold catalysts are hardly capable of giving particles that are both small and bimetallic, when the precursors in solution do not interact strongly with each other. During the subsequent thermal treatment performed to get metal particles, the metals must have enough mobility to migrate on the support, interact with each other, and form bimetallic particles. However, phase separation can be a common problem, especially when the metal ratio falls in the miscibility gap (Section 2.6), or if the intended composition is not thermodynamically stable. 

Ethanol oxidation was studied under lean conditions on platinum/alumina catalysts modified by rhodium and/or lanthanum oxide. The results on alumina support suggest that the formation of bimetallic Pt-Rh particles enhances the production of acetaldehyde, particularly after oxidizing thermal aging of the Pt-Rh/alumina catalyst prepared by coimpregnation. The addition of lanthanum oxide to alumina allows to avoid the formation of Pt-Rh alloy after high temperature treatment and therefore induces a decrease of the production of acetaldehyde. 

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