パラジウム

外観

銀白色の裁断状

定義

本品は、水中にパラジウムを懸濁させたものである。

溶解性

酸化力のある酸に溶け、水に溶けない。[塩酸3 + 硝酸1（体積比）]に溶ける。

主な性質

1. パラジウムは水素存在下の状態を除いて、化学的には安定で加工も容易な銀白色の金属
2. 白金族中、耐酸性が最も弱い。硫酸には強いが王水や熱濃硫酸には溶ける。又希硝酸には徐々に侵される。酸化剤が存在すると塩酸にも溶ける
3. 自分の体積の９００倍もの水素を水素化物として吸蔵する性質を持つ。３００℃以上に加熱されたパラジウムは水素だけを透過するが、他のガスは透過しない性質がある

解説

パラジウム,Pd．原子番号46の元素．電子配置[Kr]4d10の周期表10族貴金属または白金族元素．原子量106.42(1)．質量数102(1.02(1)％)，104(11.14(8)％)，105(22.33(8)％)，106(27.33(3)％)，108(26.46(9)％)，110(11.72(9)％)の6種の安定同位体と，質量数91～124の放射性同位体が知られている．1802年イギリスのW.H. Wollastonが王水溶液から白金を(NH4)2PtⅣ Cl6として沈殿分離したあとの溶液中に発見し，同じ年に発見された小惑星パラスにちなんで命名した．パラスはギリシア神話知恵の女神Pallas Athene．宇田川榕菴は天保8年(1837年)に出版した「舎密開宗」で，巴爾刺冑母(パルラヂウム)としている．

用途

水素添加触媒、水素燃焼触媒。

用途

触媒原料。電子・電気材料。合金材料。

用途

水素添加反応の触媒。

用途

水素反応などに使われる触媒としての用途がもっとも重要である。白金より安価なうえ軽いので各種の合金として、電気接点、歯科材料、装飾品などに使用される。

化粧品の成分用途

エモリエント剤、保湿.湿潤剤、着色剤

主な用途

1. 自動車用触媒剤（排気ガス浄化用）
2. 石油化学用触媒剤（水素化）
3. 電気、電子工業用部材（電気接点、溶接用ロー材、メッキ材、導電ペースト、プリント基板、ロボット、パソコン、光ディスク、自動車電装品）
4. 歯科用金?銀?パラジウム合金部材
5. 宝飾品（ペンダント、ブローチ、指輪等）

性質

銀白色の金属で、白金と比べ展性と硬さはやや大きいが、延性はやや劣っている。化学的性質の点で銀に似ており、他の白金族元素よりいくぶん反応性が高い。塩酸のような、いわゆる非酸化性の酸（陰イオンに酸化力のない酸）には侵されないが、希硝酸には徐々に、濃硝酸、熱濃硫酸には速やかに侵される。塩酸であっても酸素あるいは塩素が共存すれば溶解する。王水にもクロロ錯体となって溶ける。多くの気体、とくに水素を吸蔵したり透過したりする性質がある。常温で350から850倍の水素を吸収する。水素を吸収したパラジウムは外観は金属状であるが、体積は増加してもろくなり、電気伝導度も低下する。吸蔵された水素は活性で、常温でも酸素やハロゲンと反応するほか、多くの還元反応が促進される。パラジウム海綿、パラジウム黒など粉状のものは、とくにこのような性質が著しい。

物理的性質

Palladium is the middle element in group 10 of the transition elements (periods 4, 5, and6). Many of its properties are similar to nickel located above it and platinum just below it inthis group.
Palladium is a soft, silvery-white metal whose chemical and physical properties closelyresemble platinum. It is mostly found with deposits of other metals. It is malleable and ductile,which means it can be worked into thin sheets and drawn through a die to form very thinwires. It does not corrode. Its melting point is 1,554°C, its boiling point is 3,140°C, and itsdensity is 12.02 g/cm³.

同位体

There are 42 isotopes of palladium, ranging from Pd-91 to Pd-124. All but sixare radioactive and artificially produced in nuclear reactors with half-lives ranging from159 nanoseconds to 6.5×10⁺⁶ years. The six stable isotopes of palladium and theirproportional contribution to their existence in the Earth’s crust are as follows: Pd-102 =1.02%, Pd-104 = 11.14%, Pd-105 = 22.23%, Pd-106 = 27.33%, Pd-108 = 26.46%,and Pd-110 = 11.72%.

名前の由来

Palladium is named after the asteroid Pallas, which was discovered at about the same time as the element. Pallas is the name of two mythological Greek figures, one male and the other female.

天然物の起源

Palladium is considered a rare metal, making up only about 1 part per 100 million partsof the Earth’s crust. It is considered the 77th most abundant element on Earth, although it is seldom found in pure states. Rather, it is mixed with other metals or in compounds of palladium.
It was originally found in gold ores from Brazil, where the miners thought the gold wascontaminated by what they referred to as “white gold.” Later, it was considered an alloy combinationof palladium and gold.
Deposits of ores containing palladium, as well as other metals, are found in Siberia and theUral Mountains of Russia, Canada, and South Africa, as well as in South America.

特性

One of palladium’s unique characteristics is its ability to absorb 900 times its own volumeof hydrogen gas. When the surface of the pure metal is exposed to hydrogen gas (H₂), the gasmolecules break into atomic hydrogen. These hydrogen atoms then seep into the holes in thecrystal structure of the metal. The result is a metallic hydride (PdH_0.5) that changes palladiumfrom an electrical conductor to a semiconductor. The compound palladium dichloride (PdCl₂)also has the ability to absorb large quantities of carbon monoxide (CO). These characteristicsare useful for many commercial applications. Palladium is the most reactive of all the platinumfamily of elements (Ru, Rh, Pd, Os, Is, and Pt.)

使用

Palladium is a soft white metal found in copper and nickel ores. The chloride compound of this element was used after the turn of the century for printing and also in combination with platinum for printing.
Palladium is a transition metal element used in catalytic reactions involving processes such as hydrogenation. Lindlar Catalyst.
In form of gold, silver, and copper alloys in dentistry; for alloy bearings, springs, balance wheels of watches; for mirrors in astronomical instruments; as catalyzer in manufacture of sulfuric acid and in other oxidizing processes; in powder form as catalyst in hydrogenation and in ignition of hydrogen or hydrocarbons with oxygen; the spongy form is used in gas analysis for separating hydrogen from mixtures of gases.

定義

palladium: Symbol Pd. A soft whiteductile transition element (see alsoplatinum metals); a.n. 46; r.a.m.106.4; r.d. 12.02; m.p. 1552°C; b.p.3140±1°C. It occurs in some copperand nickel ores and is used in jewelleryand as a catalyst for hydrogenationreactions. Chemically, itdoes not react with oxygen at normaltemperatures. It dissolves slowly inhydrochloric acid. Palladium is capableof occluding 900 times its ownvolume of hydrogen. It forms fewsimple salts, most compounds beingcomplexes of palladium(II) with somepalladium(IV). It was discovered byWilliam Woolaston (1766–1828) in1803.

製造方法

It can be made from the ore with dry process in Industrial production; can also copper, nickel sulfide ore preparation of copper, nickel production process as a by-product as raw materials, made by wet smelting. It can also be obtained from the wet process with the byproduct of copper, nickel production from the copper sulfide ore or nickel sulfide ore.
The wet method is using the residue of extracted nickel and copper as raw materials, adding aqua for extraction, filtration, adding ammonia and hydrochloric acid to react, thus forming the precipitation of ammonium chloropalladate. After refining, filtration, reduction of ammonium chloropalladate with hydrogen 99.95% finished product of palladium can be obtained.

主な応用

Palladium is used in the preparation of Palladium catalysts. Palladium based nanomaterials can also be applied in cancer diagnosis and therapy.

調製方法

Palladium and platinum have been used since 1974 as catalyst to oxidize carbon monoxide to carbon dioxide in automobile engines and in hydrocarbon conversion. This use of palladium results in palladium being emitted as solid particles with automotive exhaust gases.

製法

原料となる陽極泥や白金鉱を王水で溶解し、白金を不溶性の沈殿として除去したあとの母液を、アンモニアおよび塩酸で処理すると、パラジウムが［PdCl2(NH3)2］となって沈殿する。これを焼けば海綿状の金属パラジウムが得られる。

一般的な説明

This product has been enhanced for energy efficiency.

危険性

Palladium is not combustible except as fine powder or dust. Several of palladium’s compoundsare oxidizing agents, and some react violently with organic substances.

燃焼性と爆発性

Palladium on carbon catalysts containing adsorbed hydrogen are pyrophoric, particularly when dry and at elevated temperatures. Palladium on carbon catalysts prepared by formaldehyde reduction are less pyrophoric than those reduced with hydrogen. Finely divided carbon, like most materials in powder form, is capable of creating a dust explosion.

貯蔵

In particular, palladium on carbon should always be handled under an inert atmosphere (preferably argon), and reaction vessels should be flushed with inert gas before the catalyst is added. Dry catalyst should never be added to an organic solvent in the presence of air. Palladium on carbon recovered from catalytic hydrogenation reactions by filtration requires careful handling because it is usually saturated with hydrogen and will ignite spontaneously on exposure to air. The filter cake should never be allowed to dry, and the moist material should be added to a large quantity of water and disposed of properly.

不和合性

Catalysts prepared on high surface area supports are highly active and readily cause ignition of hydrogen/air and solvent/air mixtures. Methanol is notable for easy ignition because of its high volatility. Addition of catalyst to a tetrahydroborate solution may cause ignition of liberated hydrogen.

廃棄物の処理

Excess palladium on carbon and waste material containing this substance should be covered in water, placed in an appropriate container, clearly labeled, and handled according to your institution's waste disposal guidelines.