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Investigation of Catalytic Oxidation and Coupling Reactions on Gold, Palladium, and Gold-Palladium Alloys

机译：金，钯和金-钯合金的催化氧化和偶联反应的研究

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摘要

Polyvinyl acetate is a common adhesive and additive to emulsion-based paints produced in the millions of tons per year through the palladium catalyzed coupling of ethylene and acetic acid. Understanding the reaction mechanism and kinetics is integral to designing a more efficient catalyst through an increase in activity, selectivity, or both. It has been shown that selectivity for the vinyl acetate monomer (VAM) reaction increases to ~94% upon alloying palladium with gold compared to palladium alone (~80% selective).;The characterization of the VAM formation reaction on Pd(111) and Au/Pd(111) single crystal alloys has been extensively studied, but it has been shown that Pd(100) and particularly Au/Pd(100) alloys have an increased activity to Pd(111) and Au/Pd(111) catalysts. Competing reaction mechanisms have also been proposed for Pd(100) catalysts for the coupling of ethylene and acetic acid. To investigate the increased reaction rate on these surfaces and to elucidate the reaction pathway the behavior of the reactants, a detailed reaction mechanism, and the kinetics of the VAM formation reaction on Pd(100) and Au/Pd(100) alloys are presented here.;Another relevant catalytic process is the oxidation of carbon monoxide on gold (typically studied on supported gold nanoparticles). This reaction is of interest as CO is a common catalyst poison that binds strongly to many reactive transition metal catalysts. It is shown that by using ozone as an atomic oxygen source, CO oxidation occurs even on Au(111) single crystals. Two CO adsorption sites are observed after ozone exposure with CO oxidation occurring at as low as ~140 K.;The Au/Pd(100) alloy catalysts were also studied for their hydrogen adsorption behavior in an attempt to reconcile differences in previous work on hydrogen adsorption on Au/Pd alloys. Hydrogen is found to adsorb in two subsurface states as well as surface chemisorbed states, that, when further exposed to CO, become trapped in the subsurface of the alloy to elevated temperatures because of CO adsorption/blocking of palladium surface sites. Upon CO desorption, hydrogen desorption occurs through now-vacant palladium surface sites.
机译：聚乙酸乙烯酯是乳液型涂料的常见粘合剂和添加剂，通过钯与乙烯和乙酸的偶合，每年可生产数百万吨。通过增加活性和/或选择性，了解反应机理和动力学是设计更有效的催化剂所不可或缺的。研究表明，与单独的钯（约80％的选择性）相比，钯与金合金化后，乙酸乙烯酯单体（VAM）反应的选择性增加至〜94％.; Pd（111）和Pd（111）上VAM形成反应的表征Au / Pd（111）单晶合金已经得到了广泛的研究，但已显示Pd（100）尤其是Au / Pd（100）合金对Pd（111）和Au / Pd（111）催化剂的活性提高。竞争性反应机理也已被提出用于Pd（100）催化剂，用于乙烯和乙酸的偶联。为了研究在这些表面上增加的反应速率并阐明反应途径，此处介绍了反应物的行为，详细的反应机理以及Pd（100）和Au / Pd（100）合金上VAM形成反应的动力学。另一个相关的催化过程是一氧化碳在金上的氧化（通常在负载型金纳米颗粒上进行研究）。由于CO是常见的催化剂毒物，可与许多反应性过渡金属催化剂牢固结合，因此该反应引起人们的关注。结果表明，使用臭氧作为原子氧源，甚至在Au（111）单晶上也会发生CO氧化。臭氧暴露后在低至〜140 K的CO氧化下观察到两个CO吸附位点;还研究了Au / Pd（100）合金催化剂的氢吸附行为，试图调和先前在氢方面的工作差异吸附在Au / Pd合金上。发现氢以两种亚表面状态以及表面化学吸附状态吸附，当氢进一步暴露于CO时，由于CO吸附/阻塞钯表面部位，氢气被截留在合金的亚表面中达到高温。一氧化碳解吸后，氢的解吸会通过现在空置的钯表面发生。

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  • 作者

    Thuening, Theodore.;

  • 作者单位

    The University of Wisconsin - Milwaukee.;

  • 授予单位 The University of Wisconsin - Milwaukee.;
  • 学科 Physical chemistry.;Chemistry.
  • 学位 Ph.D.
  • 年度 2017
  • 页码 180 p.
  • 总页数 180
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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