Палладий

Физические свойства

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.

Изотопы

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%.

Происхождение имени

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.

Вхождение

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.

Характеристики

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.)

Использование

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.

Определение

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.

Подготовка

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.

прикладной

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

Методы производства

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.

Общее описание

This product has been enhanced for energy efficiency.

Опасность

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

Воспламеняемость и взрывоопасность

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.

Описание

Палладий — переходный металл. При нормальных условиях образует кристаллы серебристо-белого цвета кубической сингонии, пространственная группа Fm3m, параметры ячейки a = 0,38902 нм, Z = 4, структурный тип меди.

Палладий пластичен, микродобавки никеля, кобальта, родия или рутения улучшают механические свойства Pd, повышают твёрдость.

Химические свойства

Палладий — редкий минерал, благородный металл платиновой группы, серебристого цвета, не тускнеющий на воздухе.Ковкий и тягучий. Более легкоплавкий по сравнению с платиной, легко прокатывается и вытягивается в проволоку. Температура плавления 1552°С. Парамагнитен. Растворим в HNO3, в горячей концентрированной Н2SO4 и царской водке. Палладий отличается чрезвычайно высоким сродством к водороду, в форме порошка способен абсорбировать объём водорода, в 900 раз превышающий собственный объём металла.

Применение

Палладий часто применяется как катализатор, в основном, в процессе гидрогенизации жиров и крекинге нефти.Хлорид палладия используется как катализатор и для обнаружения микроколичеств угарного газа в воздухе или газовых смесях.

Палладий и сплавы палладия используется в электронике — для покрытий, устойчивых к действию сульфидов (преимущество перед серебром).

В частности, палладий постоянно расходуется для производства реохордов прецизионных сопротивлений высокой точности (военная и аэрокосмическая техника), в том числе в виде сплава с вольфрамом (например, ПдВ-20М).

Производство

Палладий получают главным образом при переработке сульфидных руд никеля, серебра и меди. Некоторую часть мирового производства (около 10 %) составляет восстановление из вторичного сырья.Компактный металлический палладий получают также электроосаждением из нитритных и фосфатных кислых электролитов, например, используя Na2[Pd(NO2)4].

хранилище

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.

Несовместимости

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.

Утилизация отходов

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.