在Rh上从合成气合成乙醇的机制(111))
1Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
Journal of the American Chemical Society
|August 26, 2009
概括
基于Rh的催化剂显示出来自合成气的乙醇合成的前景. 然而,Rh{111) 有利于甲生产,需要促进剂来提高乙醇的选择性和生产力.
科学领域:
- 催化剂是一种催化剂.
- 表面科学是一门学科.
- 计算化学计算化学
背景情况:
- 来自合成气的乙醇合成对于能源应用至关重要.
- 基于Rh的催化剂提供了独特的效率,但需要机械的理解.
- 目前的挑战包括低乙醇选择性和生产力.
研究的目的:
- 通过使用DFT,研究Rh{111}上乙醇合成的分子层次机制.
- 确定控制反应速度和产品选择性的关键步骤.
- 为设计改进的基于Rh的催化剂提供见解.
主要方法:
- 密度函数理论 (DFT) 的计算.
- 对Rh的反应路径和过渡状态的分析.
- 评估基本反应步骤,包括CO化和C-C键形成.
主要成果:
- 乙醇合成始于甲基形成,其次是化和CO插入.
- 乙醇生产率低,对甲具有很高的选择性.
- 限制速率的步骤是CO化到甲基物种;选择性由甲形成和C-C合控制.
结论:
- 强烈的Rh-CO相互作用阻碍了CO化,但有助于C-O键断裂以合成乙醇.
- 促进剂对于抑制甲形成和增强C-C键形成以获得高乙醇产量至关重要.
- 这项研究为开发先进的基于Rh的催化剂提供了基础.
相关概念视频
Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
Introduction
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
Ethers from Alcohols: Alcohol Dehydration and Williamson Ether Synthesis
Overview
Ethers can be prepared from organic compounds by various methods. Some of them are discussed below,
Preparation of Ethers by Alcohol Dehydration
In this method, in the presence of protic acids, alcohol dehydrates to produce alkenes and ethers under different conditions. For example, in the presence of sulphuric acid, dehydration of ethanol at 413 K yields ethoxyethane, whereas it yields ethene at 443 K.
Ethers can be prepared from organic compounds by various methods. Some of them are discussed below,
Preparation of Ethers by Alcohol Dehydration
In this method, in the presence of protic acids, alcohol dehydrates to produce alkenes and ethers under different conditions. For example, in the presence of sulphuric acid, dehydration of ethanol at 413 K yields ethoxyethane, whereas it yields ethene at 443 K.
Reduction of Alkenes: Asymmetric Catalytic Hydrogenation
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...
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...
Production of Alcohol
Continuous fermentation is a key strategy in industrial ethanol production, particularly when efficiency, scalability, and high yields are essential. This approach allows for uninterrupted operation and optimized resource utilization. The primary feedstock, corn starch, undergoes enzymatic hydrolysis facilitated by α-amylase and glucoamylase. These enzymes break down the starch into fermentable sugars such as glucose, which are readily assimilated by fermentative microorganisms.Fermentation...
Catalysis
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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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...


