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Activity and in-situ XAS studies of promoted copper and zinc oxide catalysts for hydrogen production by methanol partial oxidation.

机译：活性和原位XAS研究用于甲醇部分氧化制氢的促进型铜和锌氧化物催化剂。

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摘要

A three step high throughput catalytic screening process was used to evaluate the activity and selectivity of copper and zinc based methanol partial oxidation catalysts. The most active catalyst preparations contained both palladium and zirconium promoters. The high activity and selectivity obtained from the doubly promoted 7Cu/3Zn/1Zr-1Pd composition suggested a synergy between palladium and zirconium promoters.;Characterization studies showed that the zirconia promoter significantly enhanced characteristics such as surface area, dispersion, crystallite size, and deactivation resistance, leading to lowered reduction temperature. However the zirconia promoter alone only slightly lowered the reaction light off temperature. Unlike zirconia, the palladium promoter did not significantly alter microstructural characteristics of the catalyst. Palladium was shown to significantly lower the reduction temperature regardless of initial CuO crystallite size, which suggests that palladium enhances the catalytic activity by increasing copper reducibility. Copper K edge x-ray absorption spectroscopy confirmed palladium promoted catalysts are more easily reduced to Cu0 under reaction conditions. Palladium x-ray absorption spectroscopy was used to determine that formation of Pd-Cu alloys is preferred over Pd-Zn alloys.;Using a four step model reaction pathway it was found that the combination of palladium and zirconia promoters significantly lowers the activation energy of the methanol combustion and steam reforming reactions. However, promoter materials do not influence the methanol decomposition and water gas shift activation energies because of the similarity of catalyst state at high reaction temperatures regardless of promoter materials. In reformer simulations it was found that approximately 5 grams of catalyst is needed to power a notebook computer.;Combustion synthesized catalysts were shown to have activity similar to bulk prepared catalysts, despite lower copper area, suggesting higher turn over rate. It was found that changing the palladium loading to the surface from the bulk did not significantly affect catalytic activity, most likely due to encapsulation of Pd by alloying with copper. An exploration of preparing structured catalysts by hydrothermal synthesis methods showed that intimate contact of copper with certain oxide phases is required for high activity.
机译：三步高通量催化筛选过程用于评估铜和锌基甲醇部分氧化催化剂的活性和选择性。活性最高的催化剂制剂同时包含钯和锆促进剂。双重促进的7Cu / 3Zn / 1Zr-1Pd组合物具有很高的活性和选择性，表明钯和锆促进剂之间具有协同作用。电阻，导致还原温度降低。然而，单独的氧化锆促进剂仅稍微降低了反应起燃温度。与氧化锆不同，钯助催化剂不会明显改变催化剂的微观结构特征。无论初始的CuO晶粒大小如何，钯均能显着降低还原温度，这表明钯可通过提高铜的还原性来增强催化活性。铜K边缘X射线吸收光谱证实，在反应条件下，钯促进的催化剂更容易还原为Cu0。使用钯X射线吸收光谱法确定Pd-Cu合金的形成优于Pd-Zn合金。;使用四步模型反应路径，发现钯和氧化锆促进剂的组合显着降低了Pd-Cu合金的活化能甲醇燃烧和蒸汽重整反应。然而，助催化剂材料不影响甲醇分解和水煤气变换活化能，因为在高反应温度下催化剂状态的相似性与助催化剂材料无关。在重整器模拟中，发现为笔记本计算机供电需要大约5克催化剂。尽管铜面积较小，但燃烧合成的催化剂显示出与批量制备的催化剂相似的活性，这表明较高的周转率。已发现改变钯从大块表面的负载量不会显着影响催化活性，这很可能是由于通过与铜合金化将Pd封装而造成的。通过水热合成方法制备结构化催化剂的探索表明，高活性需要铜与某些氧化物相的紧密接触。

著录项

  • 作者

    Schuyten, Stephen J.;

  • 作者单位

    University of Notre Dame.;

  • 授予单位 University of Notre Dame.;
  • 学科 Engineering Chemical.
  • 学位 Ph.D.
  • 年度 2008
  • 页码 264 p.
  • 总页数 264
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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