Dynamic Self-Organization of Supported Pd/Au Catalysts during Vinyl Acetate Synthesis

Abstract

It is known that vinyl acetate monomer synthesis over bimetallic Pd1Au1 catalysts is highly structurally sensitive and that these structures are dynamically formed and disintegrated in reactant gas atmosphere. Here we show via a combination of bulk and surface sensitive methods that independent of their nominal composition, Pd/Au bimetallic particles undergo marked reconstruction and phase partition during vinyl acetate synthesis. While temperature-induced reorganization of SiO2-supported PdxAuy particles leads to all three thermodynamically metastable phases, i.e., Pd3Au, Pd1Au1, PdAu3, with mainly Au-enriched surface compositions, the reactive atmosphere induces selectively the formation of the Pd1Au1 phase and separated Pd particles. The Pd in the Pd1Au1 has higher specific activity and selectivity than the sole Pd nanoparticles, exemplifying the importance of changing its electronic nature. As the Pd1Au1 phase dominates the catalytic activity, novel tailored catalysts could be produced, limiting the presence of dispersed Pd.