Carbon chemisorbed

Biyhoider G 1964 Moiecuiar orbitai view of chemisorbed carbon monoxide J. Phys. Chem. 68 2772... 

Methanol synthesis over the heterogeneous catalyst is thought to occur by a successive hydrogenation of chemisorbed carbon monoxide. 

Gutierrez, C. Potential-Modulated Reflectance Spectroscopy Studies of the Electronic Transitions of Chemisorbed Carbon Monoxide 28... 

The mode of chemisorption of CO is a key-factor concerning selectivity to various products. Hydrocarbons can only be produced if the carbon-oxygen bond is broken, whereas this bond must stay intact for the formation of oxygenates. It is obvious that catalysts favoring the production of hydrocarbons must chemisorb carbon monoxide dissociatively (e.g. Fe) while those favoring the formation of oxygenates must be able to chemisorb carbon monoxide molecularly (e.g. Rh). 

Breiter MW. 1975. Influence of chemisorbed carbon monoxide on the oxidation of molecular hydrogen at smooth platinum in sulfuric acid solution. J Electroanal Chem 65 623-634. 

Qian, Z. Pathak, B. Nisar,). Ahuja, R., Oxygen- and nitrogen-chemisorbed carbon nanostructures for Z-scheme photocatalysis applications. /. Nanoparticle Res. 2012,14 895/1-895/7. 

With the exception of the high initial heat of adsorption of CO on NiO(200), the differential heats of adsorption as a function of the amount of CO adsorbed are similar for both catalysts. Metallic nickel which exists in the sample prepared at 250°C. may chemisorb carbon monoxide (15). However, the metal content is small and cannot account for the heat released in these experiments on NiO(250), since the heat of chemisorption of CO on metallic nickel is still higher (42 kcal. per mole) than the heat registered during adsorption of the first dose (29 kcal. per mole). 

At first sight, scheme (371) does not agree with the results of our adsorption experiments these experiments showed that activated charcoal does not chemisorb CO at 100°C. It should, however, be taken into consideration that the surface of charcoal subjected to activation or even simply after storage in contact with air is covered with chemisorbed oxygen. The studies of the reactions of carbon with C02 and steam (see Section XX) have demonstrated that oxygen chemisorbed on carbon is indistinguishable from chemisorbed carbon monoxide. So it may be reckoned that activated charcoal is already covered with carbon monoxide before the contact with this gas. 

Intermolecular Interactions and the Infrared Reflection—Absorption Spectra of Chemisorbed Carbon Monoxide on Copper... 

Figure 5.5 Ways of chemisorbing carbon monoxide on a gold surface (A) linear, (B) bridged, (C) dissociated and (D) sideways on.

Fig. 14. The relation between the amounts of weakly chemisorbed carbon monoxide and irreversibly chemisorbed oxygen, indicating that these two adsorbates are a measure of copper metal surface area (43).

Fig. 15. The dependence of the amount of irreversibly chemisorbed carbon monoxide on the concentration of amorphous copper found by X-ray diffraction (Fig. 5) and by STEM (Table VI). The (10T0) prism planes of zinc oxide are exposed in the Cu/ZnO = 10/90, 20/80, and 30/70 catalysts and the (0001) basal planes of ZnO are exposed in the Cu/ZnO = 40/60, 50/50, and 67/33 catalysts. The different slopes for the two morphologies indicate slightly different concentrations of copper atoms on the prism and basal surfaces (43).

THE RELATIONSHIP BETWEEN infrared spectra of chemisorbed carbon monoxide and the catalytic activity of metais for the methanization reaction is discussed in conjunction with experiments dealing with the effect of dissolved hydrogen on the catalytic activity of nickel. The purpose of this discussion is to illustrate the type of reasoning involved in seeking a relationship between spectra of chemisorbed molecules and catalytic activity. The underlying concepts of this relationship are extended to include recent advances made in studies of the effect of the semiconductor properties of the carrier on the activity of sup -ported metal catalysts. 

The pairing of copper with platinum and nickel with palladium was reminiscent of the work of Taylor and McKinney (3) who pointed out that copper and platinum were relatively poor catalysts for the hydrogenation of carbon monoxide to methane, while nickel and palladium were active catalysts for this reaction. Although this pattern could be coincidental, it is more reasonable and productive to assume a relationship between the spectroscopic results and the catalytic activities and to conclude that metals which chemisorb carbon monoxide in... 

If the relationship is accepted, the question remains whether it shows that the bridged form of chemisorbed carbon monoxide is more easily hydrogenated or whether the structure. of the adsorbed carbon monoxide and the catalytic activity both reflect some third factor. 

The idea is not new that dissolved hydrogen can modify the activity of metal catalysts. Hall and Emmett (9) list a large number of workers who have supplied supporting evidence. Emmett, Kokes, and Hall showed that the behavior of dissolved hydrogen can be quantitatively related to the behavior Of copper-nickel alloys. This important contribution bears directly on the present discussion because the effect of adding copper to nickel is also amenable to study by means of the spectra of chemisorbed carbon monoxide. 

Early studies of carbon monoxide chemisorbed on copper-nickel alloys were complicated by the failure to realize the importance of dissolved hydrogen when the experiments were conducted (10). However recent infrared studies have shown that addition of 1 to 2% copper to nickel causes the band to shift to lower frequencies due to linear chemisorbed carbon monoxide (11). This shift supports the idea that copper and dissolved hydrogen have similar modifying effects on the electronic properties of the nickel. An argument developed below, based on the spectral changes, shows that these modifying effects are consistent with the view that electrons are transferred to the nickel. 

The foregoing discussion shows that the spectral pattern of chemisorbed carbon monoxide and the effect of adding constituents such as copper or dissolved hydrogen can be explained in a manner acceptable to most catalytic chemists. However it is not possible to outline a detailed mechanism for the methanization of carbon monoxide which similarly explains... 

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