Carbon monoxide catalytic activity

If we now consider the CO/H2 system, then the catalytic process can be envisaged as a combination of (1) and (2) above, carbon monoxide being activated by coordination and hydrogen by addition. If we adopt the view that in a transition metal hydride the hydrogen is present as an anionic hydride ligand ( H ) (49) then, given the charge separation... 

A chromia gel activated only at 150° has no detectable catalytic activity for the hydrogenation of oleflns at room temperatures nor does it chemisorb oxygen or carbon monoxide. Catalytic and adsorptive capacity develops upon pretreating the gel at higher temperatures. After heating to 400°, chromia rapidly chemisorbs oxygen and carbon monoxide at —78° and it leads to rapid hydrogenation of ethylene at -78°. 

In the second stage, a more active 2inc oxide—copper oxide catalyst is used. This higher catalytic activity permits operation at lower exit temperatures than the first-stage reactor, and the resulting product has as low as 0.2% carbon monoxide. For space velocities of 2000-4000 h , exit carbon monoxide... 

By quenching the polymerization with C1402 or Cl40 the determination of the number of propagation rate constants was found to be also possible for the two-component catalytic system TiCl2 + AlEt2Cl 158, 159). In contrast to alcohols, carbon dioxide and carbon monoxide under polymerization conditions react only with titanium-carbon active bonds and do not react with inactive aluminum-polymer bonds. 

On the surface of metal electrodes, one also hnds almost always some kind or other of adsorbed oxygen or phase oxide layer produced by interaction with the surrounding air (air-oxidized electrodes). The adsorption of foreign matter on an electrode surface as a rule leads to a lower catalytic activity. In some cases this effect may be very pronounced. For instance, the adsorption of mercury ions, arsenic compounds, or carbon monoxide on platinum electrodes leads to a strong decrease (and sometimes total suppression) of their catalytic activity toward many reactions. These substances then are spoken of as catalyst poisons. The reasons for retardation of a reaction by such poisons most often reside in an adsorptive displacement of the reaction components from the electrode surface by adsorption of the foreign species. 

Fe/Ir catalysts In situ Fe and Ir Mossbauer spectroscopy of silica-supported Fe/Ir catalysts with different iron to iridium ratios following pretreatment in hydrogen show that the reduction of the Fe component is enhanced by the presence of Ir metal. The presence of Ir was found to increase the catalytic activity in hydrogenation of carbon monoxide and also to influence selectivity... 

The carbonyl insertion step takes place by migration of the organic group from the metal to the coordinated carbon monoxide, generating an acylpalladium species. This intermediate can react with nucleophilic solvent, releasing catalytically active Pd(0). 

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... 

Heat-flow calorimetry may be used also to detect the surface modifications which occur very frequently when a freshly prepared catalyst contacts the reaction mixture. Reduction of titanium oxide at 450°C by carbon monoxide for 15 hr, for instance, enhances the catalytic activity of the solid for the oxidation of carbon monoxide at 450°C (84) and creates very active sites with respect to oxygen. The differential heats of adsorption of oxygen at 450°C on the surface of reduced titanium dioxide (anatase) have been measured with a high-temperature Calvet calorimeter (67). The results of two separate experiments on different samples are presented on Fig. 34 in order to show the reproducibility of the determination of differential heats and of the sample preparation. 

It is generally accepted that localization and coordination of monovalent Cu ions in different zeolites have significant influence on the catalytic activity. The localization and coordination of Cu ions was studied by means of adsorption of small probe molecules, in particular, carbon monoxide was used often due to its ability to form a stable mono-carbonyl complex with the Cu+ ion. The formation of this complex was investigated by the FTIR and by the microcalorimetry [1-3]. 

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