在异质的Rh-WOx对位点催化剂上进行双功能化
Insoo Ro1,2,3, Ji Qi1,3, Seungyeon Lee3,4
1Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, CA, USA.
Nature
|September 7, 2022
概括
原子分散的-氧化物 (Rh-WOx) 双位点可实现乙烯水合形成的双功能催化. 这些支持的催化剂具有很高的选择性和活性,模仿工业应用的同质催化剂.
科学领域:
- 不同质的催化
- 表面科学
- 有机金属化学
背景情况:
- 双功能活性位点对于金属催化反应至关重要,促进了催化循环中的不同步骤.
- 虽然已为同质催化剂建立,但由于结构复杂性和动态重建,在支持的金属上阐明这些位点是具有挑战性的.
- 支持的金属催化剂通常涉及金属氧化物接口作为潜在的双功能位点.
研究的目的:
- 在支持的金属催化剂上研究双功能机制的挑战.
- 合成和描述一个简化的模型系统:支持原子分散的-氧化物 (Rh-WOx) 对位点.
- 将实验动力学与双功能反应机制的理论模拟联系起来.
主要方法:
- 支持的原子分散Rh-WOx对位点催化剂的合成.
- 气相乙烯水合试验.
- 基于第一原理的微动力学模拟与实验动力学相关.
- 活性部位结构和催化性能的表征.
主要成果:
- 通过双功能机制,Rh-WOx对位点催化乙烯水合.
- 该机制涉及Rh辅助的WOx减少,从WOx转移到Rh,并在接口上进行H2解离.
- 达到>95%的选择性,产品形成速率为0.1 g的propanal cm−3 h−1.
- 证明了平均场模型对这种简化对位系统的适用性.
结论:
- 支持的氧化物对位点可以有效地实现双功能反应机制.
- 这些位点具有高活性和选择性,与同质催化剂相美.
- 这种方法为设计工业过程中先进的异质催化剂提供了途径.
相关概念视频
02:17Reduction of Alkenes: Asymmetric Catalytic Hydrogenation
3.4K
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...
3.4K
02:36Regioselectivity and Stereochemistry of Hydroboration
8.4K
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...
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...
8.4K
03:08Hydroboration-Oxidation of Alkenes
8.7K
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.
8.7K
02:24Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
8.0K
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.
8.0K
02:47Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
18.7K
Introduction
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
18.7K
01:25Radical Anti-Markovnikov Addition to Alkenes: Overview
3.5K
The addition of hydrogen bromide to alkenes in the presence of hydroperoxides or peroxides proceeds via an anti-Markovnikov pathway and yields alkyl bromides.
3.5K