Effect on CO adsorption

For alkali modified noble and sp-metals (e.g. Cu, Al, Ag and Au), where the CO adsorption bond is rather weak, due to negligible backdonation of electronic density from the metal, the presence of an alkali metal has a weaker effect on CO adsorption. A promotional effect in CO adsorption (increase in the initial sticking coefficient and strengthening of the chemisorptive CO bond) has been observed for K- or Cs-modified Cu surfaces as well as for the CO-K(or Na)/Al(100) system.6,43 In the latter system dissociative adsorption of CO is induced in the presence of alkali species.43... 

Surface pretreatment also has a marked effect on CO adsorption oxygen and carbon both inhibit carbon monoxide chemisorption and weaken the metal-adsorbate bond strength. Co-adsorbed hydrogen has no observable effects. 

There is very different behavior for the two-type adsorption states. For instance, H-type nitrogen has no effect on CO adsorption, while L-type nitrogen inhibits CO adsorption. L-type is more active for ammonia synthesis than H-type. If iron nitride was hydrogenated to ammonia, the formation rate of ammonia was also proportional to P, indicating that the H-tjrpe adsorption state of nitrogen is similar to that on iron nitride, i.e., one nitrogen atom is coordinated with several iron atoms,... 

Restructuring of a surface may occur as a phase change with a transition temperature as with the Si(OOl) surface [23]. It may occur on chemisorption, as in the case of oxygen atoms on a stepped Cu surface [24]. The reverse effect may occur The surface layer for a Pt(lOO) face is not that of a terminal (100) plane but is reconstructed to hexagonal symmetry. On CO adsorption, the reconstruction is lifted, as shown in Fig. XVI-8. 

Besides the effect of the presence of alkali on CO adsorption, there is also a stabilizing effect of adsorbed CO on the adsorption state of alkali. Within the high alkali coverage range the number of CO molecules adsorbed on promoted surface sites becomes practically equal to the number of alkali metal species and their properties are not dependent on the CO coverage. In this region CO adsorption causes also stabilization of the adsorbed alkali, as indicated by the observed high temperature shift of the onset of alkali desorption. 

Lemire C, Meyer R, Shaikhutdinov S, Freund HJ. 2004. Do quantum size effects control CO adsorption on gold nanoparticles Angew Chem Int Ed 43 118-121. 

Cuesta A, Lopez N, Gutierrez C. 2003. Electrolyte electroreflectance study of carbon monoxide adsorption on polycrystalline silver and gold electrodes. Electrochim Acta 48 2949-2956. Date M, Hamta M. 2001. Moisture effect on CO oxidation over Au/Ti02 catalyst. J Catal 201 221-224. 

The observed H2/CO effect on CO conversion can be explained considering the strong CO adsorption ability on cobalt-based catalysts. At the typical FT process conditions, in fact, it has been reported that the catalyst surface is almost... 

Also, concerning the effect of the temperature on the reaction rates, different assumptions were made here with respect to our previous work.10 In that case, only the hydrogen and CO adsorption were regarded as activated steps, in order to describe the strong temperature effect on CO conversion. In contrast, due to the insensitivity of the ASF product distribution to temperature variations (see Section 16.3.1), other steps involved in the mechanism were considered as non-activated. In the present work, however, this simplification was removed in order to take into account the temperature effect on the olefin/paraffin ratio. For this reason, Equations 16.7 and 16.8 were considered as activated. 

In 1992 the cyclic voltammogram feature of Pt single crystals in sulfuric acid solution was examined by CO adsorption. Figure 13 shows the effect of CO adsorption on Pt(lll) in sulfuric acid solution, " where at ads=0-08,0.3, and 05 V(RHE), CO gas was introduced and the current... 

Hoins, U. Charlet, L. Sticher, H. (1993) Ligand effect on the adsorption of heavy metals. The sulphate-cadmium goethite case. Water, Air, Soil Pollution 68 241-255 Holm, G. (1985) Substitution selectivity of some transition elements (Cr, Mn, Co, Ni, Cu, Zn) during formation of P-FeOOH. Geologiska Foreningsi Stockholm Forhandlingar 107 297-300... 

Thus we may conclude that the pre-adsorption of hydrogen had no effect on CO chemisorption on rhodium while both oxygen and carbon blocked many sites for CO chemisorption and weakened the metal-adsorbate interaction (Vjyj-c decreased, V( q increased,... 

Fig. 17. IR spectra of CO adsorbed at 77 K on hydrogen-precovered ZnO samples the effect of CO adsorption on the v(ZnH) modes is represented (unpublished data).

The effects of sulfur poisoning on CO adsorption are even more complex in the case of supported catalysts. Again, there are two different kinds of... 

Fig. 20. Effects of H2S on CO adsorption on 8% Ni/Al203 (open symbols denote fresh sample closed symbols denote poisoned sample) (Ref. 162).

Impedance spectra can also be used to obtain the adsorption coverage of CO, the reaction rates for CO formation and oxidation, and the effect of CO adsorption on hydrogen oxidation. In the presence of CO adsorption, H adsorption and oxidation rate can be deduced ... 

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