自動車の排気ガスの触媒は,最初の原理から: 過剰なO2の条件下での選択的なNO削減をIr上で行う
Zhi-Pan Liu1, Stephen J Jenkins, David A King
1Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
Journal of the American Chemical Society
|August 26, 2004
まとめ
過剰な酸素は窒素酸化物 (NO) の選択的減少のためのイリジウム触媒を毒化し,選択性を二酸化窒素 (NO2) 生産にシフトさせます. アルケンは,表面の酸素原子を取り除き,中毒を予防する効果的な還元剤です.
科学分野:
- 表面化学について
- カタリシス カタリシス カタリシス
- コンピューティング・マテリアル・サイエンス
背景:
- 窒素酸化物 (NO) の選択的触媒還元は,環境修復に不可欠です.
- イリジウム (Ir) 触媒は,NO還元のために調査されていますが,その性能は反応条件によって制限されることがあります.
研究 の 目的:
- 過剰酸素条件下におけるIr触媒における選択的NO減少のメカニズムを調査する.
- 触媒中毒における酸素の役割を明らかにし,それを防ぐための効果的な戦略を特定する.
主な方法:
- エネルギーデータを得るための密度関数理論 (DFT) 計算.
- 反応の可行性を評価するための熱力学的計算.
- 結合と反応機構を理解するために,電子構造の分析.
主要な成果:
- 過剰な酸素はすぐに毒を放ち,NOの削減のための触媒を活性化し,低酸素のカバーで開始します.
- アドソーブされた酸素は,選択性をN2生産からNO2生産にシフトさせます.
- イリジウムは反応条件下でIrO2に酸化することができる;アルケンは,表面炭素形成による毒化を防ぐ効果的な還元剤である.
結論:
- 酸素中毒は,Ir-触媒 NO 減少のための重要な課題です.
- 還元剤の選択は極めて重要であり,アルケンは表面酸素を除去する能力があるため,優れた性能を示す.
- アドソルバート結合競争は,酸素中毒と,NO減少における構造感受性を説明する.
さらに関連する動画
11:47The Effect of Interfacial Chemical Bonding in TiO2-SiO2 Composites on Their Photocatalytic NOx Abatement Performance
Published on: July 4, 2017
08:23Chemiluminescence-based Assays for Detection of Nitric Oxide and its Derivatives from Autoxidation and Nitrosated Compounds
Published on: February 16, 2022
関連する概念動画
02:22Reaction Yield
The theoretical yield of a reaction is the amount of product estimated to form based on the stoichiometry of the balanced chemical equation. The theoretical yield assumes the complete conversion of the limiting reactant into the desired product. The amount of product that is obtained by performing the reaction is called the actual yield, and it may be less than or (very rarely) equal to the theoretical yield.
02:50Catalysis
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.
02:31Multi-Step Reactions
Chemical reactions often occur in a stepwise fashion involving two or more distinct reactions taking place in a sequence. A balanced equation indicates the reacting species and the product species, but it reveals no details about how the reaction occurs at the molecular level. The reaction mechanism (or reaction path) provides details regarding the precise, step-by-step process by which a reaction occurs. Each of the steps in a reaction mechanism is called an elementary reaction. These...
01:13meta-Directing Deactivators: –NO2, –CN, –CHO, –CO2R, –COR, –CO2H
All meta-directing substituents are deactivating groups. These substituents withdraw electrons from the aromatic ring, making the ring less reactive toward electrophilic substitution. For example, the nitration of nitrobenzene is 100,000 times slower than that of benzene because of the deactivating effect of the nitro group. The first step in an electrophilic aromatic substitution is the addition of an electrophile to form a resonance-stabilized carbocation. The energy diagrams for the...
01:29Preparation of Amines: Reduction of Oximes and Nitro Compounds
Oximes can be reduced to primary amines using catalytic hydrogenation, hydride reduction, or sodium metal reduction. The reduction of aliphatic and aromatic nitro compounds to primary amines takes place by either catalytic hydrogenation or by using active metals like Fe, Zn, and Sn in the presence of an acid.
Though catalytic hydrogenation can reduce nitrobenzenes, the reduction is nonselective in the presence of other functional groups. For instance, if nitrobenzene contains an aldehyde group,...
Though catalytic hydrogenation can reduce nitrobenzenes, the reduction is nonselective in the presence of other functional groups. For instance, if nitrobenzene contains an aldehyde group,...
01:27Catalysis
Catalysis influences the rate of chemical reactions by providing an alternative reaction pathway with lower activation energy. A catalyst speeds up a reaction, but it is not consumed during the process. The fundamental principle of catalysis is the ability of a catalyst to alter the reaction mechanism, often introducing a more efficient pathway than the uncatalyzed process.In a catalyzed reaction, the catalyst participates directly in the reaction mechanism. It interacts with reactants to form...