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

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• 作者：Stefanie Simson ; Andreas Jentys ; Johannes A. Lercher
• 刊名：The Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：April 25, 2013
• 年：2013
• 卷：117
• 期：16
• 页码：8161-8169
• 全文大小：358K
• 年卷期：v.117,no.16(April 25, 2013)
• ISSN：1932-7455

文摘

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 Pd_xAu_y 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.