複雑な稀土アルミニウム水化物:機械化学的調製,結晶構造,水素貯蔵の可能性
Claudia Weidenthaler1, André Pommerin, Michael Felderhoff
1Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim, Germany. weidenthaler@mpi-muelheim.mpg.de
Journal of the American Chemical Society
|November 6, 2009
まとめ
新しい稀土アルミニウム水素が合成され,特徴づけられました. これらの複雑な水素は,可逆的な水素貯蔵のための低温金属水素としての潜在能力を示しています.
科学分野:
- マテリアルサイエンス 材料科学
- 固体化学 固体化学
- 無機化学 無機化学とは
背景:
- 稀土アルミニウムヒドリドは,水素貯蔵における潜在的な応用を持つ複雑な材料です.
- その構造と熱的性質を理解することは,新しいエネルギー材料の開発に不可欠です.
研究 の 目的:
- 新しく複雑な稀土アルミニウム水素を合成し,特徴づけること.
- 結晶構造,熱的安定性,脱水化行動などを調査する.
- リバーシブルな水素貯蔵の可能性を評価する.
主な方法:
- 稀土アルミニウム水化物 (REAlH(6) の機械化学製剤である.
- 結晶構造の決定のための密度関数理論 (DFT) 計算.
- 実験データを用いて構造の予備的な改良.
- デヒドロゲン化経路と製品を調査するための熱溶解研究.
- 水素化の可逆性を評価するために分解エンタルピーの分析.
主要な成果:
- 新型複合希土アルミニウム水化物 (RE=La,Ce,Pr,Nd) の合成に成功しました.
- 単離された[AlH(6) ](3-) オクタエドラを構成する三角形の結晶構造が,REイオンの橋渡しで決定された.
- 希土元素の原子番号が増加するにつれて,熱安定性の低下が観察されました.
- 稀土ヒドリド (REH(x)) とRE-アルミニウム合金 (RE-aluminium alloys) を脱水化製品として特定した.
- 計算された分解エンタルピーは,適度な条件下での可逆性水素化の可能性を示唆しています.
結論:
- 合成された稀土アルミニウム水化物は,低温水素貯蔵の有望な候補である.
- その逆転性は,最適化された圧力と温度条件で達成可能である.
- これらの材料は,エネルギー用途のための興味深い複合ヒドリドのクラスを表しています.
関連する概念動画
01:19Acid Halides to Alcohols: LiAlH4 Reduction
Acid halides are reduced to alcohols in the presence of a strong reducing agent like lithium aluminum hydride.
The mechanism proceeds in three steps. First, the nucleophilic hydride ion attacks the carbonyl carbon of the acid halide to form a tetrahedral intermediate. Next, the carbonyl group is re-formed, and the halide ion departs as a leaving group, generating an aldehyde. A second nucleophilic attack by the hydride yields an alkoxide ion, which, upon protonation, gives a primary alcohol as...
The mechanism proceeds in three steps. First, the nucleophilic hydride ion attacks the carbonyl carbon of the acid halide to form a tetrahedral intermediate. Next, the carbonyl group is re-formed, and the halide ion departs as a leaving group, generating an aldehyde. A second nucleophilic attack by the hydride yields an alkoxide ion, which, upon protonation, gives a primary alcohol as...
01:24Preparation of Aldehydes and Ketones from Nitriles and Carboxylic Acids
Although it is possible to reduce a carboxylic acid to an aldehyde, strong reducing agents, like lithium aluminum hydride (LAH), prohibit a controlled reduction, instead causing the generated aldehyde to instantly over-reduce to a primary alcohol.
Reducing carboxylic acid derivatives like acyl chlorides (RCOCl), esters (RCO2R′), and nitriles (RCN) using milder aluminum hydride agents like lithium tri-tert-butoxyaluminum hydride [LiAlH(O-t-Bu)3] and diisobutylaluminum hydride [DIBAL-H] allows...
Reducing carboxylic acid derivatives like acyl chlorides (RCOCl), esters (RCO2R′), and nitriles (RCN) using milder aluminum hydride agents like lithium tri-tert-butoxyaluminum hydride [LiAlH(O-t-Bu)3] and diisobutylaluminum hydride [DIBAL-H] allows...
01:17Esters to Alcohols: Hydride Reductions
Esters are reduced to primary alcohols when treated with a strong reducing agent like lithium aluminum hydride. The reaction requires two equivalents of the reducing agent and proceeds via an aldehyde intermediate.
Lithium aluminum hydride is a source of hydride ions and functions as a nucleophile. The mechanism proceeds in three steps. Firstly, the nucleophilic hydride ion attacks the carbonyl carbon of the ester to form a tetrahedral intermediate. Subsequently, the carbonyl group re-forms,...
Lithium aluminum hydride is a source of hydride ions and functions as a nucleophile. The mechanism proceeds in three steps. Firstly, the nucleophilic hydride ion attacks the carbonyl carbon of the ester to form a tetrahedral intermediate. Subsequently, the carbonyl group re-forms,...
01:17Carboxylic Acids to Primary Alcohols: Hydride Reduction
Carboxylic acids, upon reaction with strong reducing agents such as lithium aluminum hydride followed by hydrolysis, undergo reduction to form primary alcohols.
01:20Amides to Amines: LiAlH4 Reduction
Amide reduction with strong reducing agents like lithium aluminum hydride proceeds through a nucleophilic acyl substitution to form amines. Primary, secondary, and tertiary amides yield primary, secondary, and tertiary amines, respectively.
Amide reduction requires two equivalents of the reducing agent, acting as a source of hydride ions. As shown in the figure, the reaction is initiated with a nucleophilic attack by the hydride ion at the carbonyl carbon to form a tetrahedral intermediate.
Amide reduction requires two equivalents of the reducing agent, acting as a source of hydride ions. As shown in the figure, the reaction is initiated with a nucleophilic attack by the hydride ion at the carbonyl carbon to form a tetrahedral intermediate.
02:13Reduction of Alkenes: Catalytic Hydrogenation
Alkenes undergo reduction by the addition of molecular hydrogen to give alkanes. Because the process generally occurs in the presence of a transition-metal catalyst, the reaction is called catalytic hydrogenation.
Metals like palladium, platinum, and nickel are commonly used in their solid forms — fine powder on an inert surface. As these catalysts remain insoluble in the reaction mixture, they are referred to as heterogeneous catalysts.
The hydrogenation process takes place on the surface of...
Metals like palladium, platinum, and nickel are commonly used in their solid forms — fine powder on an inert surface. As these catalysts remain insoluble in the reaction mixture, they are referred to as heterogeneous catalysts.
The hydrogenation process takes place on the surface of...