Carbon monoxide metal purification with

The sulphide ore is oxidised in the presence of silica which enables the iron to be removed as a silicate slag. The nickel oxide left is reduced at 350° by water gas to an impure metal leaving the iron as ferric oxide. Purification is based on the formation and decomposition of gaseous Ni(CO)4. Carbon monoxide is passed over the impure metal at 60° and the gas containing a few per cent of the tetracarbonyl is brought into contact with agitated nickel pellets at 200°. The pellets grow as nickel is deposited on them the CO is recirculated (Fig. 258). 

The most common process for the chemical purification of the hydrogen rich gas is the preferential oxidation (PROX) of carbon monoxide. The preferential oxidation is promoted by precious metal based catalysts. Precious metal catalyst promotes the reaction of hydrogen and oxygen as well. So the main disadvantage of PROX is the side reaction of hydrogen with oxygen to water and heat. Furthermore precious metal based catalysts are expensive. 

As one step in its purification, nickel metal reacts with carbon monoxide to form a compound called nickel tetracarbonyl, Ni(CO)4, which is a gas at temperatures above about 316 K. A 2.00-L flask is filled with CO gas to a pressure of 748 torr at 350.0 K, and then 5.00 g of Ni is added. If the reaction described above occurs and goes to completion at constant temperature, what will the final pressure in the flask be ... 

The Dotz benzannulation reaction (DBR) is the reaction of an a,P unsaturated Fischer carbene with an alkyne to produce a highly substituted phenol. Alternatively, the DBR can be considered a metal templated 3 + 1 + 2 cycloaddition of an allylic carbine (3 carbon unit), carbon monoxide (1 carbon unit), and an alkyne (2 carbon unit). The initial product of the reaction is the arene chromium tricarbonyl complex of the phenol as in 4. These complexes are typically unstable in air such that workup and purification of the product lead to the complete loss of the metal. Chromium is the most often used metal for the benzannulation. Molybdinum, tungsten, and manganese have been used but usually give mixtures of products and require harsh reaction conditions. 

Nickel occurs, with iron, in meteorites. Its principal ores are nickelite, NiAs, millente, NiS, and pentlandite, (Ni,Fe)S. The metal is produced as an alloy containing iron and other elements, by roasting the ore and reducing with carbon. In the purification of nickel by the Mond process the compound nickel tetracarbonyl, Ni(CO)4, is manufactured and then decomposed. The ore is reduced with hydrogen to metallic nickel under conditions such that the iron oxide is not reduced. Carbon monoxide is then passed through the reduced ore at room temperature it combines with the nickel to form nickel carbonyl ... 

Copper, and particularly aluminium, are alternative metals for low temperature processes such as methanol reforming and carbon monoxide purification. The higher heat conductivity of these metals, 401 and 236 W (mK), respectively, compared with stainless steel [around 15 W (m K) j makes them attractive when isothermal conditions are required, which may well be the situation for evaporators or reactors operating vdthin narrow temperature windows. 

Transition metal atoms may also form complexes via dative hond formation. The extraction of nickel involves the formation and thermal decomposition of a transition metal complex. Nickel is usually extracted from its sulfide ore. This is roasted in air to give nickel(ii) oxide, NiO, which is then reduced by carbon to the impure metal. Refinement (purification) can be achieved by reaction with carbon monoxide at about 50 °C and normal pressure, which results in the formation of tetracarbonylnickel(O), NifCO). This complex is easily thermally decomposed to form extremely pure nickel (Mond process). 

In a low temperature purification system, the gases are then cleared of all components that, at room temperature, will react with the respective getter alloy. After this stage, the gases only contain components that do not react to metal surfaces at room temperature. The residual carbon monoxide and oxygen contents are lower than 0.1 ppm, and the water content lies below 0.5 ppm. 

Chromium metal is commercially produced in the United States by the reduction of chromite ore with carbon, aluminum, or silicon, and subsequent purification. Sodium chromate and dichromate are produced by roasting chromite ore with soda ash. Most other chromium compounds are produced from sodium chromate and dichromate (Hartford 1979 Westbrook 1979). For example, basic chromic sulfate (Cr(0H)S04), commonly used in tanning, is commercially produced by the reduction of sodium dichromate with organic compounds (e.g., molasses) in the presence of sulfuric acid or by the reduction of dichromate with sulfur dioxide. Lead chromate, commonly used as a pigment, is produced by the reaction of sodium chromate with lead nitrate or by reaction of lead monoxide with chromic acid solution (IARC 1990). 

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