在2-propanol的in situ氧化过程中,结构,化学成分和反应性相关性
Kristof Paredis1, Luis K Ono, Simon Mostafa
1Department of Physics, University of Central Florida, Orlando, Florida 32816, USA.
Journal of the American Chemical Society
|April 8, 2011
概括
小纳米粒子 (Pt NPs) 在2-醇氧化过程中表现出明显的催化行为. 氧化物是部分氧化的关键,而金属PtNP与表面氧化物在不同温度下驱动完全氧化.
科学领域:
- 催化剂是一种催化剂.
- 材料科学 材料科学 材料科学
- 表面化学 表面化学
背景情况:
- 了解反应条件下的催化剂行为对于设计高效的催化过程至关重要.
- 纳米粒子结构和化学状态显著影响催化活性和反应途径.
研究的目的:
- 为了研究纳米颗粒 (Pt NPs) 在2-醇氧化过程中的结构和化学演变.
- 为了阐明2-propanol部分和完全氧化的活性物种和反应机制.
主要方法:
- 操作式X射线吸收细结构 (XAFS) 谱学被用来研究大小选择的Pt NP (∼1 nm) 在γ-Al(2) O(3) 上.
- 该研究监测了在不同温度下对2-醇的催化氧化过程中Pt NP结构和组成的变化.
主要成果:
- 氧化物被确定为在140°C以下的部分2-propanol氧化中的活性物种.
- 金属Pt NP与表面氧化物最初催化了140°C以上的完全氧化,在200°C以上观察到氧化物再生.
- 一个中间方案显示了由于减少中间体和阻塞的O2吸附点而导致的Pt氧化物分解.
结论:
- 小型PtNP的高催化活性归因于丰富的边缘和角位,促进了反应性表面氧化物形成.
- 纳米粒子结构和化学状态在氧化催化反应的执行中起着决定性的作用.
相关概念视频
Oxidation of Alcohols
In this lesson, the oxidation of alcohols is discussed in depth. The various reagents used for oxidation of primary and secondary alcohols are detailed, and their mechanism of action is provided.
The process of oxidation in a chemical reaction is observed in any of the three forms:
The process of oxidation in a chemical reaction is observed in any of the three forms:
Oxidations of Aldehydes and Ketones to Carboxylic Acids
Oxidation of aldehydes and ketones results in the formation of carboxylic acids. Aldehydes, bearing hydrogen next to the carbonyl group, are easily oxidized compared to ketones. This is because an aldehydic proton can easily be abstracted during oxidation.
Aldehydes readily undergo oxidation in strong oxidizing agents such as potassium permanganate and chromic acid. The oxidation can also be carried out using mild oxidizing agents such as silver oxide. In fact, aldehydes can be easily oxidized...
Aldehydes readily undergo oxidation in strong oxidizing agents such as potassium permanganate and chromic acid. The oxidation can also be carried out using mild oxidizing agents such as silver oxide. In fact, aldehydes can be easily oxidized...
Hydroboration-Oxidation of Alkenes
In addition to the oxymercuration–demercuration method, which converts the alkenes to alcohols with Markovnikov orientation, a complementary hydroboration-oxidation method yields the anti-Markovnikov product. The hydroboration reaction, discovered in 1959 by H.C. Brown, involves the addition of a B–H bond of borane to an alkene giving an organoborane intermediate. The oxidation of this intermediate with basic hydrogen peroxide forms an alcohol.
Preparation of Aldehydes and Ketones from Alcohols, Alkenes, and Alkynes
Aldehydes and ketones are prepared from alcohols, alkenes, and alkynes via different reaction pathways. Alcohols are the most commonly used substrates for synthesizing aldehydes and ketones. The conversion of alcohol to aldehyde, which involves the oxidation process, depends on the class of the alcohol used and the strength of the oxidizing agent. For instance, primary alcohol will form an aldehyde when treated with a weak oxidizing agent; however, it gets over-oxidized to a carboxylic acid in...
Regioselectivity and Stereochemistry of Hydroboration
A significant aspect of hydroboration–oxidation is the regio- and stereochemical outcome of the reaction.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
Oxidative Cleavage of Alkenes: Ozonolysis
In ozonolysis, ozone is used to cleave a carbon–carbon double bond to form aldehydes and ketones, or carboxylic acids, depending on the work-up.
Ozone is a symmetrical bent molecule stabilized by a resonance structure.
Ozone is a symmetrical bent molecule stabilized by a resonance structure.


