Hydrogen carbon monoxide, competition

From the results of other authors should be mentioned the observation of a similar effect, e.g. in the oxidation of olefins on nickel oxide (118), where the retardation of the reaction of 1-butene by cis-2-butene was greater than the effect of 1-butene on the reaction of m-2-butene the ratio of the adsorption coefficients Kcia h/Kwas 1.45. In a study on hydrogenation over C03O4 it was reported (109) that the reactivities of ethylene and propylene were nearly the same (1.17 in favor of propylene), when measured separately, whereas the ratio of adsorption coefficients was 8.4 in favor of ethylene. This led in the competitive arrangement to preferential hydrogenation of ethylene. A similar phenomenon occurs in the catalytic reduction of nitric oxide and sulfur dioxide by carbon monoxide (120a). 

If hydrogen gas is added to the reaction mixture of J, and 11 the hydrogenolysis reaction of thorium-to-carbon sigma bonds (J-1 22) allows interception of species 13 and thus, catalytic hydrogenation of the inserted carbon monoxide functionality. At 35 C under 0.75 atm initial H2 pressure with [JJ =9.0 x 10" M and [ 1JJ = 6.5 x 10" M, hydrogenation and isomerization are competitive and both the enolate and the alkoxide reduction product 14 are produced (eq.(13)). Under these conditions, turnover fre-... 

COMPETITIVE OXIDATION OF CARBON MONOXIDE IN THE PRESENCE OF HYDROGEN... 

It has long been known that carbon monoxide acts as a competitive inhibitor of most hydrogenases. This indicates that CO and hydrogen compete for the same binding site in the enzyme. EPR studies showed that under certain conditions, CO can directly bind to nickel (Van der Zwaan et al. 1986,1990) in the Nia-C state. Both, the Nia-C state and the induced. 

Wood distillation was used previously in the U.S. to make methanol, acetic acid, and acetone. Up to 1-2% per wood weight of methanol, 4-5% acetic acid, and 0.5% acetone can be obtained. Many years ago this was the only source of these compounds. It is no longer competitive with the synthetic processes. Some phenols can be obtained, as well as common gases such as carbon dioxide, carbon monoxide, methane, and hydrogen. 

In this chapter, recent results are discussed In which the adsorption of nitric oxide and its Interaction with co-adsorbed carbon monoxide, hydrogen, and Its own dissociation products on the hexagonally close-packed (001) surface of Ru have been characterized using EELS (13,14, 15). The data are interpreted In terms of a site-dependent model for adsorption of molecular NO at 150 K. Competition between co-adsorbed species can be observed directly, and this supports and clarifies the models of adsorption site geometries proposed for the individual adsorbates. Dissociation of one of the molecular states of NO occurs preferentially at temperatures above 150 K, with a coverage-dependent activation barrier. The data are discussed in terms of their relevance to heterogeneous catalytic reduction of NO, and in terms of their relationship to the metal-nitrosyl chemistry of metallic complexes. 

There should not be independent adsorption sites for each reactant they should adsorb competitively, carbon monoxide much more strongly than hydrogen. 

To account for the final stage of hydroformylation, Heck and Bres-low a) suggested the intermediacy of coordinately unsaturated acylcobalt tricarbonyls, which are reduced to aldehydes by hydrogen or converted into tetracarbonyls by carbon monoxide. The well known adverse effect of carbon monoxide on die course of the oxo reaction may, therefore, be attributed to this competition. 

A related group of compounds is that of the gold(III) dimethyl(alkoxycarbonyl) complexes, accessible by the reaction of carbon monoxide with dimethyl(alkoxy)(triphenyl-phosphine)gold(III), which is prepared in situ from cw-[AuIMe2(PPli3)] and sodium alkoxide in methanol (equation 80)353,359. Thermolysis of the methoxycarbonyl complex in benzene leads to the reductive elimination of methyl acetate and ethane, indicating competition between the two modes of decomposition illustrated in Scheme 27. The reaction of the same complex with electrophiles such as hydrogen chloride proceeds with liberation of carbon monoxide and methanol, as illustrated in equation 81. 

Fischer and Tropsch assumed an intermediate formation of carbides (carbide theory) as mechanism of the reaction of carbon monoxide and hydrogen to higher hydrocarbons. Methane was assumed to be formed via an intermediate formation of hydrides. The competition of carbon monoxide and hydrogen in connection with the formation of carbides and hydrides was considered to be responsible for the tendency of different catalysts to form preferentially either higher hydrocarbons or methane. With this theory, Fischer and Tropsch explained why iron presented an... 

A second assumption is that CO and dihydrogen absorb competitively in molecular form on the remaining surface sites. Because Sexton and Somorjai s temperature-programmed desorption studies (12) show that molecularly chemisorbed CO is desorbed rapidly from the rhodium surface only above 250°C at 10" Torr, virtual saturation of these associ-atively adsorbing sites by carbon monoxide can be assumed to occur at 300°C and 50 atm. The fact that molecular hydrogen does not compete... 

Carbon monoxide and hydrogen production data behave similarly, and reach a maximum at about 5 sec residence time and 700 to 750 C. Data for C2 Hg production show some similarity to that of CH4 however, C2 Hg production reaches a maximum at temperatures of 650° to 700°C and residence times of about 2 sec. Competitive rates of formation by pyrolysis and consumption by pyrolysis or dehydrogenation reactions probably explain this observed behavior. 

MedUn, J. W., McDaniel, A. H., Allendorf, M. D. and Bastasz, R. (2003), Effects of competitive carbon monoxide adsorption on the hydrogen response of metal-insulator-semiconductor sensors the role of metal film morphology,/ourna/ of Applied Physics, 93(4), 2267-74. 

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