The role of alloying in catalytic properties: Pd-Au bimetals for vinyl acetate synthesis

Mingshu Chen, Patrick Han, Fan Yang, D. Wayne Goodman

    研究成果: Conference contribution

    抄録

    Bimetallic catalysts exhibit markedly different properties from either of the constituent metals, and enhanced catalytic performance. Surface composition is a key to understanding the role of alloying in mixed-metal catalysts. Scanning tunneling microscopy (STM), low-energy ion scattering spectroscopy (LEIS), infrared reflection absorption spectroscopy (IRAS) and temperature programmed desorption (TPD) using CO as a probe molecule were used to elucidate the surface concentration and adsorption sites as well as the surface ensembles. PdAu(100), Pd/Au-low index single crystal surfaces, and planar model surface of Pd-Au/Mo(110) were selected as model surfaces. Isolated Pd sites, PdAu6 for Pd-Au on Mo(110) and for Pd/Au(111), and PdAu4 for PdAu(100) and Pd/Au(100), were observed by controlling the Pd amount and the annealing temperature. Acetoxylation of ethylene to vinyl acetate (VA) was used to investigate the mechanism of the promotional effect of Au in a Pd-Au alloy catalyst. The enhanced rates of VA formation for low Pd coverages relative to high Pd coverages on Au single crystal surfaces demonstrate that the critical reaction site for VA synthesis consists of two, non-contiguous, suitably spaced Pd monomers. The results show that the role of Au is to isolate single Pd sites that facilitate the coupling of critical surface species to product while inhibiting the formation of undesirable reaction by-products.

    本文言語English
    ホスト出版物のタイトル233rd ACS National Meeting, Abstracts of Scientific Papers
    出版ステータスPublished - 2007 12 28
    イベント233rd ACS National Meeting - Chicago, IL, United States
    継続期間: 2007 3 252007 3 29

    出版物シリーズ

    名前ACS National Meeting Book of Abstracts
    ISSN(印刷版)0065-7727

    Other

    Other233rd ACS National Meeting
    CountryUnited States
    CityChicago, IL
    Period07/3/2507/3/29

    ASJC Scopus subject areas

    • Chemistry(all)
    • Chemical Engineering(all)

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