Oxide scales processes

Thus, the growth of an external oxide scale by the reaction between a pure metal or a metallic alloy and a gaseous or liquid oxidant phase at high temperature is also a combination of diffusion processes and interfacial reactions, and Fig. 2.1 also applies to such corrosion processes that are formally similar to solid-state reactions in poly-phase and multi-constituent systems. Such a similarity will be considered to extend the treatment of the Kirkendall effect for two-phase diffusion couples to the growth of an oxide scale on a pure metal or on an alloy. The roles of interfaces will be analysed more particularly in relation to some specific topics related to oxide scaling processes such as interface displacement, growth stresses and injection of point defects (vacancy or interstitial). 

The alkalized zinc oxide—chromia process developed by SEHT was tested on a commercial scale between 1982 and 1987 in a renovated high pressure methanol synthesis plant in Italy. This plant produced 15,000 t/yr of methanol containing approximately 30% higher alcohols. A demonstration plant for the lEP copper—cobalt oxide process was built in China with a capacity of 670 t/yr, but other higher alcohol synthesis processes have been tested only at bench or pilot-plant scale (23). 

Metal Treatment. After rolling, the oxide scale on sheet steel is removed by acid treatment (pickling) (see Metal surface treatments). Phosphoric acid, a good pickling agent, leaves the steel coated with a thin film of iron phosphates. This process improves mst resistance but presents a problem if the steel is to be electroplated. 

Butylene Oxide. Butylene oxides are prepared on a small scale by Dow by chlorohydrin technology. There appears to be no technical reason why they could not be prepared by the propylene oxide Oxirane process (see Chlorohydrins). 

Directed Oxidation of a Molten Metal. Directed oxidation of a molten metal or the Lanxide process (45,68,91) involves the reaction of a molten metal with a gaseous oxidant, eg, A1 with O2 in air, to form a porous three-dimensional oxide that grows outward from the metal/ceramic surface. The process proceeds via capillary action as the molten metal wicks into open pore channels in the oxide scale growth. Reinforced ceramic matrix composites can be formed by positioning inert filler materials, eg, fibers, whiskers, and/or particulates, in the path of the oxide scale growth. The resultant composite is comprised of both interconnected metal and ceramic. Typically 5—30 vol % metal remains after processing. The composite product maintains many of the desirable properties of a ceramic however, the presence of the metal serves to increase the fracture toughness of the composite. 

Concern for the conservation of energy and materials maintains high interest in catalytic and electrochemistry. Oxygen in the presence of metal catalysts is used in CUPROUS ION-CATALYZED OXIDATIVE CLEAVAGE OF AROMATIC o-DIAMINES BY OXYGEN (E,Z)-2,4-HEXADIENEDINITRILE and OXIDATION WITH BIS(SALI-CYLIDENE)ETHYLENEDIIMINOCOBALT(II) (SALCOMINE) 2,6-DI-important industrial method, is accomplished in a convenient lab-scale process in ALDEHYDES FROM OLEFINS CYCLOHEXANE-CARBOXALDEHYDE. An effective and useful electrochemical synthesis is illustrated in the procedure 3,3,6,6-TETRAMETHOXY-1,4-CYCLOHEX ADIENE. ... 

If the PBR is less than unity, the oxide will be non-protective and oxidation will follow a linear rate law, governed by surface reaction kinetics. However, if the PBR is greater than unity, then a protective oxide scale may form and oxidation will follow a reaction rate law governed by the speed of transport of metal or environmental species through the scale. Then the degree of conversion of metal to oxide will be dependent upon the time for which the reaction is allowed to proceed. For a diffusion-controlled process, integration of Pick s First Law of Diffusion with respect to time yields the classic Tammann relationship commonly referred to as the Parabolic Rate Law ... 

That work led to a routine 700 gram scale oxide reduction process that has been in use since that time. Recent development work at LANL has increased the batch size to one kilogram of oxide feed. It appears that the ultimate limitation on DOR batch size will be from criticality safety constraints. 

Multiple fluid streams in medium- to large-scale processes become important for many oxidation reactions. MicroChannel operation allows safe operation in the explosive regions [42, 43], but this advantage ceases as the dimensions become... 

Selox [Selective oxidation] A process for selectively oxidizing methane to syngas using a proprietary heterogeneous catalyst at temperatures up to 1,000°C. Developed on a laboratory scale by TRW, CA, partly financed by the U.S. Department of Energy in 1983. 

Karl Bosch (1874-1940) and Alwin Mittasch (1869-1953) of Badische Anilin- und Soda-Fabrik eliminated the nitrate shortage that occurred after the British sea blockade effectively cut off the nitrate supply from Chile. By May of 1915, they had successfully developed at their Oppau Plant an industrial-scale process for oxidizing ammonia. Their process converted the large quantities of synthetic ammonia produced by the Haber process to nitric acid and other nitrates that were essential for fertilizers and explosives. (10)... 

A full-scale design that has effectively increased cell power requirements by 50 percent to achieve the required destruction efficiencies in spite of efforts to demonstrate good electrochemical or coulombic efficiency earlier studies of mediated electrochemical oxidation (MEO) processes anticipated this outcome, noting that low coulombic... 

Another full-scale process combines catalytic oxidation including biodegradation, adsorption, precipitation/flocculation, and reverse osmosis [120]. 

Reaction of sulfonamide 145 with /-BuOCl in 7-propyl acetate affords A -chlorinated sulfonamide 146 in 92% yield (Equation 21) <2005TL1099>. These conditions provide an attractive industrial-scale process for Bu OCl formation, as this oxidant is created in situ upon the slow addition of NaOCl to a solution of /-BuOH and AcOH, thereby reducing heat generation. 

Federsel, H.-J. and Larsson, M. An Innovative Asymmetric Sulfide Oxidation The Process Development History behind the New Antiulcer Agent Esomeprazole in Asymmetric Catalysis on Industrial Scale, Blaser, H.U. and Schmidt, E. (Eds). Wiley-VCH New York, 2004, 413 36. 

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