Carbonyl refining process

The more common carbonyl refining process involves reaction of crude nickel with carbon monoxide under pressure at 100°C to form nickel tetracar-bonyl, Ni(CO)4. The liquid tetracarbonyl upon heating at 300°C decomposes to nickel metal and carbon monoxide. Very pure nickel can be obtained by the carbonyl refining processes, as no other metal forms a simdar carbonyl under these conditions. 

Ni is found in many ores in combination with S, As Sb, the chief sources being the minerals chalcopyrite, pyrrhotite and pentlandite. Ni ores are of two types, sulfide and oxide, the former accounting for two-thirds of the world s consumption. Sulfide ores are refined by flotation and roasting to sintered Ni oxide, and either sold as such or reduced to metal, which is cast into anodes and refined electrolytically or by the carbonyl (Mond) process. Oxide ores are treated by hydrometallurgjcal refining, eg, leaching with ammonia. Much secondary Ni is recovered from scrap (Refs 6 7) 1... 

Two U.S. patents issued to the Barium Steel Corporation in 1957 claim the formation of the heptacarbonyls M(CO)7 (M = Ti, Zr, Hf) as intermediates for the purification of these metals (9,10). In this described refining process, the finely divided metal is treated with CO at 300-400°C and 4-8 atm. The resulting liquid heptacarbonyl compound is then thermally dissociated to the pure metal and CO. The alleged existence of these binary carbonyls seems highly unlikely without supporting evidence. 

Tetracarbonylnickel is colorless and odorless but extremely toxic (carcinogenic), and no leakage, down to the part-per-billion detection limit, can be tolerated in the plant. This has undoubtedly discouraged more widespread use of carbonyl refining in place of the usual electrolytic processes (see Section 17.5). 

The MCM v3 mechanism for butane was found to provide an acceptable reaction framework for describing the NOx-photo-oxidation experiments on the above systems, although a number of parameter modifications and refinements were identified and introduced which resulted in an improved performance. These generally relate to the magnitude of sources of free radicals from carbonyl photolysis processes, which are currently under review in MCM development activities. Specifically, recommendations are made to update the photolysis parameters for HCHO, MEK, either in line with data reported since the MCM mechanism development protocol (Jenkin et ai, 1997), or on the basis of optimization in the current study. 

A special refining process is the carbonyl nickel process, an old process, which was invented in 1902 in Wales and used as the Langer-Mond process. Originally the plant treated nickel-copper matte but the process today is highly modified. The principle is a treatment at 60°C with carbon monoxide at atmospheric pressure. Nickel carbonyl, Ni(CO) is formed. This is a volatile Kquid that melts at -19.3°C and boils at 42.5°C. In this process nickel (and some iron) is carried off while other metals remain. Heating the gas to 180°C decomposes it and pure nickel powder is obtained. 

Ca.rbonylProcess. Cmde nickel also can be refined to very pure nickel by the carbonyl process. The cmde nickel and carbon monoxide (qv) react at ca 100°C to form nickel carbonyl [13463-39-3] Ni(CO)4, which upon further heating to ca 200—300°C, decomposes to nickel metal and carbon monoxide. The process is highly selective because, under the operating conditions of temperature and atmospheric pressure, carbonyls of other elements that are present, eg, iron and cobalt, are not readily formed. 

According to the free energy change associated with the pertinent reaction, nickel will form nickel tetracarbonyl at low temperatures, and this carbonyl will become unstable and revert back to nickel and carbon monoxide at moderate temperatures. The Mond process for refining nickel is based on these features. In this process, impure nickel is exposed to carbon monoxide gas at 50 °C, whereby volatile nickel tetracarbonyl (Ni(CO)4) forms. No impurity present in the crude nickel reacts with carbon monoxide. Since formation of the... 

Platinum also is used extensively as a catalyst in hydrogenation, dehydrogenation, oxidation, isomerization, carbonylation, and hydrocracking. Also, it is used in organic synthesis and petroleum refining. Like palladium, platinum also exhibits remarkable abdity to absorb hydrogen. An important application of platinum is in the catalytic oxidation of ammonia in Ostwald s process in the manufacture of nitric acid. Platinum is installed in the catalytic converters in automobile engines for pollution control. 

Ruthenium is derived from platinum metal ores. Method of production depends on the type of ore. However, the extraction processes are simdar to those of other nohle metals (see Platinum, Rhodium and Iridium). Ruthenium, like Rhodium, may he obtained from accumulated anode sludges in electrolytic refining of nickel or copper from certain types of ores. Also, residues from refining nickel by Mond carbonyl process contain ruthenium and other precious metals at very low concentrations. The extraction processes are very lengthy, involving smelting with suitable fluxes and acid treatments. 

Sulfide ores are processed by a number of pyrometallurgical processes roasting, smelting, and converting. During these processes, sulfur and iron are removed to deld a sulfur-deficient copper-nickel matte. Especially after roasting and converting, the nickel in the matte may consist primarily of nickel subsulfide. After physical separation of the copper and nickel sulfides, the nickel is refined electrochemically or by the carbonyl process. The treatment of the matte depends on the end use of the nickel. Alternatively, the sulfide can be roasted to form a nickel oxide sinter that is used directly in steel production. 

Acetic Acid. Although at the time of this writing Monsanto s Rh-catalyzed methanol carbonylation (see Section 7.2.4) is the predominant process in the manufacture of acetic acid, providing about 95% of the world s production, some acetic acid is still produced by the air oxidation of n-butane or light naphtha. n-Butane is used mainly in the United States, whereas light naphtha fractions from petroleum refining are the main feedstock in Europe. 

In (1) the electrolytic process, a nickel of 99.9% purity is produced, along with slimes which may contain gold, silver, platinum, palladium, rhodium, iridium, ruthenium, and cobalt, which are subject to further refining and recovery. In (2) the Mond process, the nickel oxide is combined with carbon monoxide to form nickel carbonyl gas, Ni(CO)4. The impurities, including cobalt, are left as a solid residue. Upon fuitlier heating of the gas to about 180°C, the nickel carbonyl is decomposed, the freed nickel condensing on nickel shot and the carbon monoxide recycled. The Mond process also makes a nickel of 99.9% purity. 

As mentioned earlier, nickel carbonyl is a volatile intermediate in the Mond process for nickel refining. This compound also is used for vapor plating of nickel in the semiconductor industry, and as a catalyst in the chemical and petrochemical industries. The toxicity of the compound has been known for many years Exposure of laboratory animals to the compound has induced a number of ocular anomalies, including aiioplidialiiiiaandinicrophtlialmia, and has been shown to be a carcinogenic for rats. 

Although nickel carbonyl is intensely poisonous, it is used in the Mond process for the refinement of nickel (see Section 16.3). Complex formation is also responsible for carbon monoxide s toxicity it attaches more strongly than oxygen to the iron in hemoglobin and prevents it from accepting oxygen from the air in the lungs. As a result, the victim suffocates. 

With continuing refinements to the rhodium-catalyzed, liquid-phase, methanol carbonylation technology (see Section 2.1.2.1.5), this industrial process will remain the most competitive route to acetic acid, well into the 21 st century. 

One of the earliest industrial CVD applications developed during this stage is a carbonyl process for refining nickel (Ni), developed by Mond in 1890 [9, 10], The famous Mond extraction process uses the following chemical reaction process ... 

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