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相关概念视频

Heterogeneous Catalysis01:22

Heterogeneous Catalysis

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Heterogeneous catalysis involves a catalyst in a different phase from the reactants. It is a process where the catalyst and the reactants are in distinct phases, typically solid and gas or liquid.Most heterogeneous catalysts are metals, metal oxides, or acids. The list includes transition metals like iron (Fe), cobalt (Co), nickel (Ni), palladium (Pd), platinum (Pt), chromium (Cr), manganese (Mn), tungsten (W), silver (Ag), and copper (Cu). These metals possess partially vacant d orbitals that...
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Catalysis02:50

Catalysis

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The presence of a catalyst affects the rate of a chemical reaction. A catalyst is a substance that can increase the reaction rate without being consumed during the process. A basic comprehension of a catalysts’ role during chemical reactions can be understood from the concept of reaction mechanisms and energy diagrams.
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Reduction of Alkenes: Asymmetric Catalytic Hydrogenation02:17

Reduction of Alkenes: Asymmetric Catalytic Hydrogenation

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Catalytic hydrogenation of alkenes is a transition-metal catalyzed reduction of the double bond using molecular hydrogen to give alkanes. The mode of hydrogen addition follows syn stereochemistry.
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
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Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide02:44

Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide

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Alkenes are converted to 1,2-diols or glycols through a process called dihydroxylation. It involves the addition of two hydroxyl groups across the double bond with two different stereochemical approaches, namely anti and syn. Dihydroxylation using osmium tetroxide progresses with syn stereochemistry.
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Alkenes via Reductive Coupling of Aldehydes or Ketones: McMurry Reaction01:22

Alkenes via Reductive Coupling of Aldehydes or Ketones: McMurry Reaction

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The radical dimerization of ketones or aldehydes gives vicinal diols through a pinacol coupling reaction. However, the behavior of titanium metals used for the reaction as a source of electrons is unusual. When the reaction is carried out in the presence of titanium, diols can be isolated at low temperatures. Else titanium further reacts with diols, forming alkenes through the McMurry reaction.
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Olefin Metathesis Polymerization: Overview01:13

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Recently, the development of olefin metathesis polymerization advanced the field of polymer synthesis. Simply put, the reorganization of substituents on their double bonds between two olefins in the presence of a catalyst is known as the olefin metathesis reaction. The use of metathesis reaction for polymer synthesis is called olefin metathesis polymerization.
Ruthenium-based Grubbs catalyst is the most commonly used catalyst for olefin metathesis polymerization. Grubbs catalyst consists of a...
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Synthesis and Testing of Supported Pt-Cu Solid Solution Nanoparticle Catalysts for Propane Dehydrogenation
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双金属铜催化剂的协同效应提高了氧化合反应的选择性

Konstantinos A Goulas1,2,3, Sanil Sreekumar1,3, Yuying Song4

  • 1Department of Chemistry, University of California , Berkeley, California 94720, United States.

Journal of the American Chemical Society
|May 20, 2016
PubMed
概括
此摘要是机器生成的。

将铜添加到催化剂可以显著减少凝结反应中不必要的脱碳化,通过C-C键形成增强高分子量氧化物的产生.

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科学领域:

  • 催化剂
  • 材料科学
  • 有机化学

背景情况:

  • 像格尔贝特和阿尔多尔这样的凝结反应对于C-C键的形成和合成高分子量氧化物至关重要.
  • (Pd) 支持酸是一种活性催化剂,但受到显著的脱碳化作用.

研究的目的:

  • 开发一种更有选择性的冷凝反应催化剂.
  • 在保持高催化活性的同时减轻脱碳.

主要方法:

  • 使用X射线衍射 (XRD),扩展X射线吸收精细结构 (EXAFS),传输电子显微镜 (TEM) 和CO化学吸收/温度编程吸收 (TPD) 的CuPd双金属纳米颗粒的合成和表征.
  • 密度函数理论 (DFT) 计算以调查反应机制和催化剂表面特性.

主要成果:

  • 与单独使用Pd相比,Pd-Cu (3:1) 双金属催化剂显著降低了脱碳化.
  • 鉴定发现Cu-缩表面的CuPd双金属纳米粒子.
  • DFT研究表明,表面Cu原子增强了反应性,而CO选择性地毒害了负责脱碳的Pd位点.

结论:

  • 通过抑制脱碳化,CuPd双金属催化剂为凝结反应提供了更好的选择性.
  • 丰富的表面和Pd位点的选择性中毒是提高性能的关键.
  • 这种双金属方法提供了一种有效生产更高分子量氧化物的途径.