Oxygen oxidized carbon monoxide

G. Fisher and co-workers, "Mechanism of the Nitric Oxide—Carbon Monoxide—Oxygen Reaction Over a Single Crystal Rhodium Catalyst," in M. 

High levels of sulfur not only form dangerous oxides, but they also tend to poison the catalyst in the catalytic converter. As it flows over the catalyst in the exliaust system, the sulfur decreases conversion efficiency and limits the catalyst s oxygen storage capacity. With the converter working at less than maximum efficiency, the exhaust entering the atmosphere contains increased concentrations, not only of the sulfur oxides but also, of hydrocarbons, nitrogen oxides, carbon monoxides, toxic metals, and particulate matter. 

Determination of oxygen. The sample is weighed into a silver container which has been solvent-washed, dried at 400 °C and kept in a closed container to avoid oxidation. It is dropped into a reactor heated at 1060 °C, quantitative conversion of oxygen to carbon monoxide being achieved by a layer of nickel-coated carbon (see Note). The pyrolysis gases then flow into the chromatographic column (1 m long) of molecular sieves (5 x 10-8 cm) heated at 100 °C the CO is separated from N2, CH4, and H2, and is measured by a thermal conductivity detector. 

The most successful class of active ingredient for both oxidation and reduction is that of the noble metals silver, gold, ruthenium, rhodium, palladium, osmium, iridium, and platinum. Platinum and palladium readily oxidize carbon monoxide, all the hydrocarbons except methane, and the partially oxygenated organic compounds such as aldehydes and alcohols. Under reducing conditions, platinum can convert NO to N2 and to NH3. Platinum and palladium are used in small quantities as promoters for less active base metal oxide catalysts. Platinum is also a candidate for simultaneous oxidation and reduction when the oxidant/re-ductant ratio is within 1% of stoichiometry. The other four elements of the platinum family are in short supply. Ruthenium produces the least NH3 concentration in NO reduction in comparison with other catalysts, but it forms volatile toxic oxides. 

The ionization probabilities It vary over some five decades across the elements in the periodic table. In addition, they vary also with the chemical environment of the element. This effect, usually referred to as the matrix effect, makes quantitation of SIMS spectra extremely difficult. As illustrated in Table 4.1, positive secondary ion yields from metal oxides are typically two orders of magnitude higher than those of the corresponding metals. A similar increase in yields from metals is observed after adsorption of gases such as oxygen or carbon monoxide. 

Figure 3.7 An anti-smoking device the cigarette is inserted into the wider end. Partially oxidized carbon monoxide combines chemically with oxygen inside the device after leaving the end of the cigarette but before entering the smoker s mouth the oxygen necessary to effect this oxidation enters the device through the small circular holes positioned along its length...

The increase of the catalytic activity in the room-temperature oxidation of carbon monoxide, which results from the increase of the temperature of preparation of NiO from 200° to 250°C., is related to the difference in the reactivity of oxygen adsorbed on both surfaces. The interaction between adsorbed oxygen and carbon monoxide has roughly the same velocity on both oxides. But on NiO (200) this interaction yields only C02(ads)> whereas on NiO(250) the same interaction produces C03"(ads) on the most active sites (anionic vacancies) and C02(g) on the less... 

Another important application of heterogeneous catalysts is in automobile catalytic converters. Despite much work on engine design and fuel composition, automotive exhaust emissions contain air pollutants such as unburned hydrocarbons (CxHy), carbon monoxide, and nitric oxide. Carbon monoxide results from incomplete combustion of hydrocarbon fuels, and nitric oxide is produced when atmospheric nitrogen and oxygen combine at the high temperatures present in an... 

G. Fisher and co-workers, "Mechanism of the Nitric Oxide—Carbon Monoxide—Oxygen Reaction Over a Single Crystal Rhodium Catalyst," in M. J. Philips and M. Teman, eds., Proceedings of the 9th International Congress on Catalysis, Vol 3, Characterisation and Metal Catalysts, Chemical Institute of Canada, Ottawa, 1988. 

Oxygen and carbon monoxide, however, are regarded as incapable of associating in the above maimer, their molecules being mutually inert in flames. Before the carbon monoxide can undergo oxidation, the oxygen must either have dissociated, or be in the form of some... 

Draw an electron dot diagram for CN. Determine the oxidation number of each element, and compare with the oxidation numbers of carbon and oxygen in carbon monoxide, which has the same number of electrons. Why is there a difference ... 

The catalysts were evaluated by exposure to a simulated automobile exhaust gas stream composed of 0.2% isopentane, 2% carbon monoxide, 4% oxygen and a balance of nitrogen. The temperature required to oxidize the isopentane and carbon monoxide was used to compare catalyst performance. The chromium-promoted catalyst oxidized isopentane at the lowest temperature, and a mixed chromium/copper-promoted catalyst proved the most efficient for oxidizing carbon monoxide and isopentane. It is interesting to note that the test rig used a stationary engine with 21 pounds of catalyst. Although the catalyst was very effective it is difficult to envisage uranium oxide catalysts employed for emission control of mobile sources. 

Goldan P. D., Trainer M., Kuster W. C., Parrish D. D., Carpenter J., Roberts J. M., Yee J. E., and Fehsenfeld F. C. (1995) Measurements of hydrocarbons, oxygenated hydrocarbons, carbon monoxide, and nitrogen oxides in an urban basin in Colorado imphcations for emissions inventories. J. Geophys. Res. 100, 22771-22785. 

A kinetic model [15], with adapted kinetic parameters [25], was used, which accounts for oxidation by oxygen of carbon monoxide, propene, methane, and hydrogen, and also includes inhibition effects caused by nitrogen oxide. The following net production rates were applied in Eq. (26) ... 

An intensive review (F. S. Stone) examines experimental work and interpretation of interactions where the reactants (A, B, etc.) are some of the simple gases, oxygen, hydrogen, carbon monoxide, and carbon dioxide, and the catalyst (X) is one of a few selected oxide solids. We are carried to vivid realization of the importance of electronic phenomena by the experiences of photon-influenced chemisorption and catalysis on these solids. 

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