Carbon monoxide oxidation promoters

Lithium, promotion of carbon monoxide oxidation, 74, 293 Long range effects, 189... 

Oscillatory reactions carbon monoxide oxidation, 388 electrochemical promotion of, 389 Overpotential activation, 124 anodic, 122 cathodic, 122 cell, 123... 

Petersson, M, Jonsson. D. Persson, H. Cruise, N. and Andersson, B. Ozone promoted carbon monoxide oxidation on platimum/y-alumina catalyst / Catai., 2006, 2S8y 321-329... 

Yu et al. [104] also have found a positive effeet of lanthanum for carbon monoxide oxidation catalysts (Au/Ti02). They noted that lanthanum improved the activity, a fact that was assigned to the presence of lanthamun promoting the reactivity of CO adsorbed on gold sites and to the formation of a second active phase on the surface. It was observed that lanthanum increased the specific surface area and restrained the growth of titania partieles. 

The lower temperatures and reduced degree of oxygen starvation in LPO (vs VPO) generally reduce carbon monoxide production markedly by promoting reaction 18 and suppressing reaction 21. As a consequence, acids, from further oxidation of aldehydes, are usually the main products. 

PGM catalyst technology can also be appHed to the control of emissions from stationary internal combustion engines and gas turbines. Catalysts have been designed to treat carbon monoxide, unbumed hydrocarbons, and nitrogen oxides in the exhaust, which arise as a result of incomplete combustion. To reduce or prevent the formation of NO in the first place, catalytic combustion technology based on platinum or palladium has been developed, which is particularly suitable for appHcation in gas turbines. Environmental legislation enacted in many parts of the world has promoted, and is expected to continue to promote, the use of PGMs in these appHcations. 

The feed to the shift converter contains large amounts of carbon monoxide which should be oxidized. An iron catalyst promoted with chromium oxide is used at a temperature range of 425-500°C to enhance the oxidation. 

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. 

Park PW, Ledford JS (1998) The influence of surface structure on the catalytic activity of cerium promoted copper oxide catalysts on alumina oxidation of carbon monoxide and methane. Catal Lett 50(1—2) 41 48... 

Figure 2.8 The surface reaction between adsorbed carbon monoxide and hydrogen to methane over rhodium catalysts occurs at lower temperatures in the presence of a vanadium oxide promoter, which is known to enhance the rate of CO dissociation (from Koerts el al. 113]). 

Electronic ligand effects are highly predictable in oxidative addition reactions a-donors strongly promote the formation of high-valence states and thus oxidative additions, e.g. alkylphosphines. Likewise, complexation of halides to palladium(O) increases the electron density and facilitates oxidative addition [11], Phosphites and carbon monoxide, on the other hand, reduce the electron density on the metal and thus the oxidative addition is slower or may not occur at all, because the equilibrium shifts from the high to the low oxidation state. In section 2.5 more details will be disclosed. 

One of the simplest examples for such effects is the oxidation of ammonia with iron oxide-bismuth oxide as a catalyst. Here, the addition of bismuth oxide results in the formation of nitrous oxides as the main product whereas an iron oxide catalyst without bismuth oxide yields nitrogen almost exlcusively. Selectively guiding catalysts become increasingly important in the synthesis of organic compounds, e.g., in the hydrogenation of carbon monoxide where the type of obtainable product can be varied, within wide limits, by the kinds of catalysts and promoters which are employed. 

Utilize combustion promoter to catalyze oxidation of carbon monoxide in the dense bed if already in nse, increase addition rate [7]... 

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