ジヒドリドマグネシウム

化学的特性Pure magnesium hydride is a white, nonvolatile powder. Although its properties are predominantly salt-like, it shows signs of a transition towards the covalent polymeric hydride structure of compounds such as beryllium and aluminum hydride. Magnesium hydride decomposes without melting at 280 ℃. Its reactivity depends on the method of preparation. The product obtained by direct synthesis from the elements is stable in air. Nevertheless, if it is prepared by pyrolysis of dialkyl magnesium or by reaction of lithium aluminum hydride with dimethyl magnesium, the product is very pure and finely divided and ignites spontaneously on contact with air.

解説水素化マグネシウムとは、化学式MgH2で表される無機化合物です。 灰色または白色のの結晶性固体で、水または湿った空気と接触すると発火する可能性があります。水素化マグネシウムは、最大 7.6 重量%の水素を吸蔵可能です。 他のや水素吸蔵物質と比較し吸蔵量が多いこと、また地球上に原料が豊富に存在することから、水素貯蔵体として研究が進められています。水素化マグネシウムを加水分解することで、水素が得られます。

説明MgH2 contains 7.66% by weight of hydrogen and has been studied as a potential hydrogen-storage medium. It was discovered in 1912, during the pyrolysis of ethyl magnesium iodide (a Grignard reagent), which produced small amount of MgH2. In 1951, preparation from the elements was first reported involving direct hydrogenation of Mg metal at high pressure and temperature (200 atmospheres, 500°C)with magnesium iodide as a catalyst: Mg＋H2→MgH2 Lower temperature production from Mg and H2 using nano-crystalline Mg produced in ball mills has been investigated. Other preparations include: 1. The hydrogenation of magnesium anthracene under mild conditions: Mg(anthracene)＋H2→MgH2＋C14H10 2. The reaction of diethyl magnesium with LiAlH4 3. An adduct of complexed MgH2, e.g. MgH2·THF by the reaction of phenylsilane (C6H8Si) and dibutyl magnesium in ether or hydrocarbon solvents in the presence of THF (C4H8O) using TMEDA (Tetramethylethylenediamine＝(CH3)2NCH2CH2N (CH3)2) as a ligand.

使用Magnesium hydride contains a high proportion of hydrogen (7.65 wt %), which can be liberated by heat. The catalytically produced compound displays rapid rates of hydrogenation and dehydrogenation and it is therefore of interest as a hydrogen reservoir. The high activity of catalytically produced magnesium hydride also enables it to take part in an addition reaction with 1-alkenes to form organomagnesium compounds:MgH2+2 CH2 = CHR→Mg（CH2CH2R）2These dialkylmagnesium compounds have become industrially important in the production of very active Ziegler catalysts. The Mg – H2 system can also be used for the simultaneous removal and purification of pure hydrogen from gas mixtures. Magnesium hydride is also used as a drying agent for organic solvents and gases and in chemical syntheses.

一般的な説明Magnesium hydride is a white crystalline solid. Magnesium hydride reacts violently with water and may ignite upon contact with air. Magnesium hydride is used to make other chemicals.

使用用途1. 水素貯蔵材料 水素化マグネシウムは、常温・常圧で安定し、安全性が高く、多くの水素を貯蔵できる性質です。水素貯蔵材料として、盛んに研究が行われています。 2. 燃料電池車 (FCV) 燃料電池車は、水素と酸素の化学反応で発電し、排出物が水のみであることから、クリーンエネルギーとして認知されています。マグネシウムタブレットや、マグネシウム粉末などを水素化炉にて高温・高圧環境下で水素と反応させることで製造します。固体やペースト場にすることで、カートリッジに格納可能となり、水素キャリアとすることができます。 また、水素化マグネシウムは金属系吸蔵材料ですが、従来型よりも軽量である点が特徴です。アルミよりもさらに軽量であることから、将来的な実用化が期待されています。 3. 民生用用途 水素化マグネシウムは、産業用への利用の他に、水素水、水素風呂、入浴剤、美容・理容用途などへの適用も進められています。

Magnesium hydride is synthesized industrially from the elements at 300 – 400 ℃ and 10 – 15 MPa hydrogen pressure in a rotary autoclave provided with steel grinding balls:Mg+H2→MgH2The commercial product is gray due to the presence of impurities, being about 97 % pure (Ventron). Less drastic reaction conditions are required when a homogeneous catalyst is used. The hydrogenation can be carried out at 60 – 70 ℃and 8 MPa in THF in the presence of halides of chromium, titanium, or iron and magnesium – anthracene complex. In contrast to the product from an uncatalyzed synthesis, this has a high specific surface area (90 m2 /g compared with 0.5 m2 /g), and is very reactive and pyrophoric.