Oxidation with air

Impurities can be removed by formation of a gaseous compound, as in the fire-refining of copper (qv). Sulfur is removed from the molten metal by oxidation with air and evolution of sulfur dioxide. Oxygen is then removed by reduction with C, CO, in the form of natural gas, reformed... 

Ma.nufa.cture. Several nickel oxides are manufactured commercially. A sintered form of green nickel oxide is made by smelting a purified nickel matte at 1000°C (30) a powder form is made by the desulfurization of nickel matte. Black nickel oxide is made by the calcination of nickel carbonate at 600°C (31). The carbonate results from an extraction process whereby pure nickel metal powder is oxidized with air in the presence of ammonia (qv) and carbon dioxide (qv) to hexaamminenickel(TT) carbonate [67806-76-2], [Ni(NH3)3]C03 (32). Nickel oxides also ate made by the calcination of nickel carbonate or nickel nitrate that were made from a pure form of nickel. A high purity, green nickel oxide is made by firing a mixture of nickel powder and water in air (25). 

Cumene Process. There are several Hcensed processes to produce phenol which are based on cumene (qv) (1,8—11). AH of these processes consist of two fundamental chemical reactions cumene is oxidized with air to form cumene hydroperoxide, and cumene hydroperoxide is cleaved to yield phenol and acetone. In this process, approximately 0.46 kg of acetone and 0.75 kg of phenol are produced per kg of cumene feedstock. 

Herm/es/Djnamit JS obe/Process. On a worldwide basis, the Hercules Inc./Dynamit Nobel AG process is the dorninant technology for the production of dimethyl terephthalate the chemistry was patented in the 1950s (67—69). Modifications in commercial practice have occurred over the years, with several variations being practiced commercially (70—72). The reaction to dimethyl terephthalate involves four steps, which alternate between liquid-phase oxidation and liquid-phase esterification. Two reactors are used. Eirst, -xylene is oxidized with air to -toluic acid in the oxidation reactor, and the contents are then sent to the second reactor for esterification with methanol to methyl -toluate. The toluate is isolated by distillation and returned to the first reactor where it is further oxidized to monomethyl terephthalate, which is then esterified in the second reactor to dimethyl terephthalate. 

Adipic acid (qv) has a wide variety of commercial uses besides the manufacture of nylon-6,6, and thus is a common industrial chemical. Many routes to its manufacture have been developed over the years but most processes in commercial use proceed through a two-step oxidation of cyclohexane [110-83-8] or one of its derivatives. In the first step, cyclohexane is oxidized with air at elevated temperatures usually in the presence of a suitable catalyst to produce a mixture of cyclohexanone [108-94-1] and cyclohexanol [108-93-0] commonly abbreviated KA (ketone—alcohol) or KA oil ... 

The oxidative coupling of 2,6-dimethylphenol to yield poly(phenylene oxide) represents 90—95% of the consumption of 2,6-dimethylphenol (68). The oxidation with air is catalyzed by a copper—amine complex. The poly(phenylene oxide) derived from 2,6-dimethylphenol is blended with other polymers, primarily high impact polystyrene, and the resulting alloy is widely used in housings for business machines, electronic equipment and in the manufacture of automobiles (see Polyethers, aromatic). A minor use of 2,6-dimethylphenol involves its oxidative coupling to... 

Chemical Properties. The most significant chemical property of L-ascorbic acid is its reversible oxidation to dehydro-L-ascorbic acid. Dehydro-L-ascorbic acid has been prepared by uv irradiation and by oxidation with air and charcoal, halogens, ferric chloride, hydrogen peroxide, 2,6-dichlorophenolindophenol, neutral potassium permanganate, selenium oxide, and many other compounds. Dehydro-L-ascorbic acid has been reduced to L-ascorbic acid by hydrogen iodide, hydrogen sulfide, 1,4-dithiothreitol (l,4-dimercapto-2,3-butanediol), and the like (33). 

Diacetone-L-sorbose (DAS) is oxidized at elevated temperatures in dilute sodium hydroxide in the presence of a catalyst (nickel chloride for bleach or palladium on carbon for air) or by electrolytic methods. After completion of the reaction, the mixture is worked up by acidification to 2,3 4,6-bis-0-isoptopyhdene-2-oxo-L-gulonic acid (2,3 4,6-diacetone-2-keto-L-gulonic acid) (DAG), which is isolated through filtration, washing, and drying. With sodium hypochlorite/nickel chloride, the reported DAG yields ate >90% (65). The oxidation with air has been reported, and a practical process was developed with palladium—carbon or platinum—carbon as catalyst (66,67). The electrolytic oxidation with nickel salts as the catalyst has also... 

Direct l eaching of Concentrates. Sherri tt Gordon Mines, Ltd., has adapted the process first used on nickel sulfide ores to zinc sulfide oxidation with air in aqueous slurry under pressure (42,43). The concentrates are leached direcdy with return acid from the cells and the sulfide is converted to free sulfur ... 

The desilverized alloy now contains bismuth as well as lead and ziac. To remove the lead and ziac, advantage is taken of the fact that ziac and lead chlorides are formed before bismuth chloride [7787-60-2J, BiCl, when the alloy is treated at 500°C with chlorine gas. Ziac chloride [7646-85-7] ZnCl, forms first, and after its removal lead chloride [7758-95-4], PbCl2, forms preferentially. This process is continued until the desired level of lead removal has been reached. The bismuth is given a final oxidation with air and caustic soda the refined product has a purity of 99.999%. 

Oxidation with air of sulfides in ores to oxides or sulfates that are more easily processed for metal recoveiy. 

Chloride process. This process requires a high titanium feedstock. Rutile is reacted with hydrochloric acid to produce titanium tetrachloride, which can be hydrolyzed with steam or oxidized with air to render the dioxide. A rutile form of titanium dioxide is obtained. 

The ferric sulfide can be oxidized with air to produce sulfur and regenerate the ferric oxide. The reaction for ferric oxide regeneration is as follows ... 

Phenol, CeHsOH (hydroxybenzene), is produced from cumene by a two-step process. In the first step, cumene is oxidized with air to cumene hydroperoxide. The reaction conditions are approximately 100-130°C and 2-3 atmospheres in the presence of a metal salt catalyst ... 

A related reaction involves oe-substituted aryl nitriles having a sufficiently acidic a hydrogen, which can be converted to ketones by oxidation with air under phase-... 

Cyclooctadiene is reacted with bromine to make fire-retardants. Cyclododecane is oxidized with air and then nitric acid to make a diacid containing 12 carbons. This acid is used to prepare some types of nylon, and its esters are used in synthetic lubricating oils. 

Selective catal3ftic oxidation with air of glycerol and oxygenated derivatives on platinum metals... 

These Rh-containing phases are mixed with NaOH and 2-ethylhexanoic acid and subsequently oxidized with air, H202, or other oxidizing agents. The Rh compounds in phase 1 and 2 are thus converted to Rh 2-ethylhexanoate and are extracted in a crossflow manner by means of 2-ethylhexanol. The recovery rate of rhodium is 97-98%. The residual water phase ends up in the fraction for external work-up as described above. 

American Also known as the Wetherill process, and the Direct process. A process for making zinc oxide, in the form of a white pigment, from a zinc oxide ore. The ore is usually franklinite, which is predominately ZnFe204. The ore is mixed with coal and heated in a furnace to approximately 1,000°C, forming zinc vapor in a reducing atmosphere. The vapors pass to a second chamber in which they are oxidized with air, forming zinc oxide and carbon dioxide. See also French. 

Amoco Amoco Chemicals Company, a subsidiary of Amoco Corporation, formerly Standard Oil Company (IN), is best known in the chemicals industry for its modification of the Mid-Century process for making pure terephthalic acid. /7-Xylene in acetic acid solution is oxidized with air at high temperature and pressure. Small amounts of manganese, cobalt, and bromide are used as catalysts. The modification allows the use of terephthalic acid, rather than dimethyl terephthalate, for making fiber. The process can also be used for oxidizing other methylbenzenes and methylnaphthalenes to aromatic carboxylic acids. See also Maruzen. 

Claus A process for removing hydrogen sulfide from gas streams by the catalyzed reaction with sulfur dioxide, producing elementary sulfur. The process has two stages in the first, one third of the hydrogen sulfide is oxidized with air to produce sulfur dioxide in the second, this sulfur dioxide stream is blended with the remainder of the hydrogen sulfide stream and passed over an iron oxide catalyst at approximately 300°C. The resulting sulfur vapor is condensed to liquid sulfur. 

Cuprasol Also called EIC. A process for removing hydrogen sulfide and ammonia from geothermal steam by scrubbing with an aqueous solution of copper sulfate. The resulting copper sulfide slurry is oxidized with air, and the copper sulfate re-used. The sulfur is recovered as ammonium sulfate. Developed by the EIC Corporation, MA, and demonstrated by the Pacific Gas Electric Company at Geysers, CA, in 1979. 

Dowa A flue-gas desulfurization process in which the sulfur dioxide is absorbed in a basic aluminum sulfate solution. The product solution is oxidized with air and reacted with limestone to produce gypsum. Developed by the Dowa Mining Company, Japan, in the early 1980s. In 1986 it was in use in nine plants in Japan and the United States. 

TRW Meyers [Named after the three CalTech professors who founded the company Thompson, Ramo, and Wooldridge] A chemical method for desulfurizing coal. The iron pyrites is leached out with a hot aqueous solution of ferric sulfate, liberating elemental sulfur. The resulting ferrous sulfate solution is re-oxidized with air or oxygen ... 

Hydrogen sulfide is recovered from the scmbbing solution under vacuum, hence the name. It is then either oxidized with air and the sulfur dioxide used for making sulfuric acid, or converted to elemental sulfur by the Claus process. The process is suitable only for gases not containing ammonia. Developed by Krupp Koppers, Germany. Three units were being built in 1993. 

Sulfur trioxide is not only much cheaper than hexachloroplatinate, but the sulfur dioxide formed can in principle be converted back to sulfur trioxide by oxidation with air. Methylbisulfate can be hydrolyzed to methanol, and so a complete cycle that converts CH4 and 02 into CH3OH can be envisioned. Overoxidation of methane to C02 - a major side reaction of many procedures - was relatively limited in the... 

The rare earth metals. The rare earth metals are extremely reactive elements especially with respect to the normal atmospheric gases. The light trivalent lanthanides oxidize with air at room temperature they should be stored (and handled) in vacuum or under He or Ar. Divalent Eu oxidizes much more readily than any of... 

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