Resistance to Carbon Monoxide

Refractories tend to deposit carbon in a carbon monoxiderich atmosphere. The reaction is given in Equation 19.1 [7]. 

Any free iron in the refractory acts as the nucleation site for this deposition. The free iron gets converted to iron carbide in the process. When iron carbide grows, it leads to the disintegration of the refractory. 

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A [NiFe]-Hydrogenase Resistant to Carbon Monoxide and Oxygen... 

ISO 12676 2000 Refractory products - determination of resistance to carbon monoxide... 

Assessment of refractories for resistance to carbon monoxide attack therefore takes place at 450°C (BS 1902-3.10) (4) and approximately 500°C for ASTM C288-87 (3) and ISO 12676 2000. Refractory prisms are placed in a sealed furnace into which a stream of carbon monoxide is introduced. The test pieces are visually inspected at regular intervals throughout the test duration, nominally 200 hours or until disintegration takes place, and their appearance noted. 

Interestingly, in the inverse-electron-demand Diels-Alder reactions of oxepin with various enophiles such as cyclopentadienones and tetrazines the oxepin form, rather than the benzene oxide, undergoes the cycloaddition.234 236 Usually, the central C-C double bond acts as dienophile. Oxepin reacts with 2,5-dimethyl-3,4-diphenylcyclopenta-2,4-dienone to give the cycloadduct 6 across the 4,5-C-C double bond of the heterocycle.234 The adduct resists thermal carbon monoxide elimination but undergoes cycloreversion to oxepin and the cyclopenta-dienone.234... 

Fig. 3.29 Resistances of the 38 sensor segments of a Sn02-microarray equipped with Si02-membrane during alternating exposure to carbon monoxide contaminated humid air and clean air with the same relative humidity...

In operation, the gases enter at diametrically opposite sides of the cylindrical combustion chamber. It is here that much carbonyl fluoride is formed and much heat is liberated. If flow rates are too high, the heat of the reaction may ignite copper in contact with fluorine. The capacity of the apparatus to produce trifluoromethyl hypo-fluorite appears to be limited by the rate of removal of heat from this reactor. A mixing chamber made from copper, nickel. Monel metal, or other fluorine-resistant metal should be satisfactory, provided that adequate provision is made for removal of heat. Suitable rates of flow for the apparatus described are fluorine, about 5 l./hour carbon monoxide, about 2 to 2.3 l./hour. The limiting rates have not been established. It is important that the ratio by volume of fluorine to carbon monoxide be somewhat more than 2 1. 

For PEMFG, the water management is critical to the fuel cell performance Excess water at the positive electrode leads to flooding of the membrane dehydration of the membrane leads to the increase of ohmic resistance. In addition, the catalyst of the membrane is sensitive to carbon monoxide poisoning. In practice, pure hydrogen gas is not economical to mass produce. Thus, hydrogen gas is typically produced by steam reforming of hydrocarbons, which contains carbon monoxide. 

This temperature prevails at the blast furnace stack. On deposition of carbon, the brick develops a crack and disintegrates. Hence, bricks meant to be used in the construction of a blast furnace stack should be tested for resistance to carbon deposition. This is done by holding a sample of the bricks in a stream of carbon monoxide at 450°C for 200 h. The sample is inspected at frequent intervals for any signs of carbon deposition, cracking, or disintegration. 

The materials of constmction of the radiant coil are highly heat-resistant steel alloys, such as Sicromal containing 25% Cr, 20% Ni, and 2% Si. Triethyi phosphate [78-40-0] catalyst is injected into the acetic acid vapor. Ammonia [7664-41-7] is added to the gas mixture leaving the furnace to neutralize the catalyst and thus prevent ketene and water from recombining. The cmde ketene obtained from this process contains water, acetic acid, acetic anhydride, and 7 vol % other gases (mainly carbon monoxide [630-08-0][124-38-9] ethylene /74-< 3 -/7, and methane /74-< 2-<7/). The gas mixture is chilled to less than 100°C to remove water, unconverted acetic acid, and the acetic anhydride formed as a Hquid phase (52,53). 

Boron carbide is resistant to most acids but is rapidly attacked by molten alkalies. It may be melted without decomposition in an atmosphere of carbon monoxide, but is slowly etched by hydrogen at 1200°C. It withstands metallic sodium fairly well at 500°C and steam at 300°C (8). 

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