Oxygen manufacturing methods

Gra.de A. Types I and II both represent the requirements of the USP XX (26). The USP tests arose from original formal oxygen specifications made necessary by the low purity and certain contaminants, particularly CO and CO2, contributed by early chemical and cryogenic manufacturing methods. Containers marked Oxygen-USP must also indicate whether or not the gas has been produced by the air Hquefaction process (see also Fine chemicals). 

Using nitrile oxides, various compounds and materials possessing valuable properties have been prepared. Among them are thin-film resistors useful for a thermal head and comprising a nitrile oxide, ruthenium and oxygen, a method for manufacturing the resistor by coating or deposition (529), isoxazole and/or isoxazoline polyheterocyclic systems like 458, which are useful for development of a new class of ionophores (530). 

The second manufacturing method for propylene oxide is via peroxidation of propylene, called the Halcon process after the company that invented it. Oxygen is first used to oxidize isobutane to r-butyl hydroperoxide (BHP) over a molybdenum naphthenate catalyst at 90°C and 450 psi. This oxidation occurs at the preferred tertiary carbon because a tertiary alkyl radical intermediate can be formed easily. 

Classifications of Fused Silica and Methods of Manufacture. Methods of manufacture that involve gas-oxygen combustion as a heat source allow considerably more water vapor (a product of combustion) to be incorporated within the glass structure as hydroxyl ions than do electric melting methods. Synthetic precursors, as opposed to naturally occurring minerals, allow greater chemical purity. These two factors, heat source and raw material source (natural versus synthetic) have lead to a commonly accepted classification of fused silica types (after Heatherington et al. and Bruckner ) ... 

In some cases, particularly with iaactive metals, electrolytic cells are the primary method of manufacture of the fluoroborate solution. The manufacture of Sn, Pb, Cu, and Ni fluoroborates by electrolytic dissolution (87,88) is patented. A typical cell for continous production consists of a polyethylene-lined tank with tin anodes at the bottom and a mercury pool (ia a porous basket) cathode near the top (88). Pluoroboric acid is added to the cell and electrolysis is begun. As tin fluoroborate is generated, differences ia specific gravity cause the product to layer at the bottom of the cell. When the desired concentration is reached ia this layer, the heavy solution is drawn from the bottom and fresh HBP is added to the top of the cell continuously. The direct reaction of tin with HBP is slow but can be accelerated by passiag air or oxygen through the solution (89). The stannic fluoroborate is reduced by reaction with mossy tin under an iaert atmosphere. In earlier procedures, HBP reacted with hydrated stannous oxide. 

Another method of manufacture involves the oxidation of 2-isopropylnaphthalene ia the presence of a few percent of 2-isopropylnaphthalene hydroperoxide/i)ti< 2-22-(y as the initiator, some alkaU, and perhaps a transition-metal catalyst, with oxygen or air at ca 90—100°C, to ca 20—40% conversion to the hydroperoxide the oxidation product is cleaved, using a small amount of ca 50 wt % sulfuric acid as the catalyst at ca 60°C to give 2-naphthalenol and acetone in high yield (70). The yields of both 2-naphthalenol and acetone from the hydroperoxide are 90% or better. 

Nickel sulfate also is made by the reaction of black nickel oxide and hot dilute sulfuric acid, or of dilute sulfuric acid and nickel carbonate. The reaction of nickel oxide and sulfuric acid has been studied and a reaction induction temperature of 49°C deterrnined (39). High purity nickel sulfate is made from the reaction of nickel carbonyl, sulfur dioxide, and oxygen in the gas phase at 100°C (40). Another method for the continuous manufacture of nickel sulfate is the gas-phase reaction of nickel carbonyl and nitric acid, recovering the soHd product in sulfuric acid, and continuously removing the soHd nickel sulfate from the acid mixture (41). In this last method, nickel carbonyl and sulfuric acid are fed into a closed-loop reactor. Nickel sulfate and carbon monoxide are produced the CO is thus recycled to form nickel carbonyl. 

Processes that are essentially modifications of laboratory methods and that allow operation on a larger scale are used for commercial preparation of vinyhdene chloride polymers. The intended use dictates the polymer characteristics and, to some extent, the method of manufacture. Emulsion polymerization and suspension polymerization are the preferred industrial processes. Either process is carried out in a closed, stirred reactor, which should be glass-lined and jacketed for heating and cooling. The reactor must be purged of oxygen, and the water and monomer must be free of metallic impurities to prevent an adverse effect on the thermal stabiUty of the polymer. 

Chloroform can be manufactured from a number of starting materials. Methane, methyl chloride, or methylene chloride can be further chlorinated to chloroform, or carbon tetrachloride can be reduced, ie, hydrodechlorinated, to chloroform. Methane can be oxychlorinated with HCl and oxygen to form a mixture of chlorinated methanes. Many compounds containing either the acetyl (CH CO) or CH2CH(OH) group yield chloroform on reaction with chlorine and alkali or hypochlorite. Methyl chloride chlorination is now the most common commercial method of producing chloroform. Many years ago chloroform was almost exclusively produced from acetone or ethyl alcohol by reaction with chlorine and alkali. 

To remain safe and efficacious on the eye, contact lenses must maintain clear and wetted surfaces, provide an adequate supply of atmospheric oxygen to and adequate expulsion of carbon dioxide from the cornea, allow adequate flow of the eye s tear fluid, and avoid excessive abrasion of the ocular surface or eyeflds, all under a variety of environmental conditions. The clinical performance of a contact lens is controlled by the nature of the lens material the lens design the method and quaUty of manufacture the lens parameters or specifications prescribed by the practitioner and the cleaning, disinfection, and wearing procedures used by the patient. 

Density. Measurement of the density of water by pycnometry is the classical method (30) for estabHshing deuterium concentrations in heavy water. Very precise measurements can be made by this method, provided the sample is prepared free of suspended or dissolved impurities and the concentration of oxygen-18 in water is about 0.2 mol %. However, in nearly all heavy water manufactured since 1950 in the United States, the... 

The proper method to remove the catalyst involves stabilization. The method for this is usually recommended by the catalyst manufacturer. With the reactor still closed, cold and flushed with nitrogen, admit nitrogen with less than 1 % oxygen in it, while the impeller is running. This oxidizes the organics and the metallic surface of the catalyst under well-controlled conditions after which the catalyst can be exposed to air without danger of overheating. 

Rare earth metals, as well as alkali earth metals, can be used as oxygen getters in the purification of tantalum powder. Osaku and Komukai [608] developed a method for the production of tantalum and niobium metal powder by a two-step reduction of their oxides. The second step was aimed at reducing the oxygen content and was performed by thermal treatment with the addition of rare metals. The powder obtained by the described method is uniform, had a low oxygen level and was suitable for application in the manufacturing of tantalum capacitors. 

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