Atomic species adsorbed

The role of oxygen and hydrogen solutions in the metal catalyst does not appear to be that of impeding the major reactions, but merely to provide a source of these reactants which is uniformly distributed diroughout the catalyst particles, without decreasing die number of surface sites available to methane adsorption. It is drerefore quite possible that a significatit fraction of the reaction takes place by the formation of products between species adsorbed on the surface, and dissolved atoms just below the surface, but in adjacent sites to the active surface sites. 

Adsorbed Atomic Species as Intermediates in Heterogeneous Catalysis Carl Wagner... 

C. Wagner, Adsorbed Atomic Species as Intermediates in Heterogeneous Catalysis, in Adv. Catal., (1970), pp. 323-381. 

In this chapter we have largely relied on computational chemistry, in particular on density-functional theory. Quantum mechanical calculations of a macroscopic piece of metal with various species adsorbed on it are as yet impossible, but it is possible to obtain realistic results on simplified systems. One approach is to simulate the metal by a cluster of 3-30 atoms on which the molecule adsorbs and then describe all the involved orbitals. Many calculations have been performed on this basis with many useful results. Obviously, the cluster must be sufficiently large that the results do not represent an artefact of the particular cluster size chosen, which can be verified by varying the cluster size. 

Asymmetric diarylmethanes, hydrogenolytic behaviors, 29 229-270, 247-252 catalytic hydrogenolysis, 29 243-258 kinetics and scheme, 29 252-258 M0O3-AI2O3 catalyst, 29 259-269 relative reactivity, 29 255-257 schematic model, 29 254 Asymmetric hydrogenations, 42 490-491 Asymmetric synthesis, 25 82, 83 examples of, 25 82 Asymmetry factor, 42 123-124 Atom-by-species matrix, 32 302-303, 318-319 Atomic absorption, 27 317 Atomic catalytic activities of sites, 34 183 Atomic displacements, induced by adsorption, 21 212, 213 Atomic rate or reaction definition, 36 72-73 structure sensitivity and, 36 86-87 Atomic species, see also specific elements adsorbed... 

The condensation of 2-hydroxyacetophenone with benzaldehyde yielded exclusively 2 -hydroxy-chalcone, and the cyclization to flavanone was not observed. An investigation of the species adsorbed on the catalyst (289) suggested that CS condensation on the Ba(OH)2 surface occurs via a very rigid transition state, whereby the OH group of 2-hydroxyacetophenone is bonded to the catalyst surface and placed at great distance from the carbonyl carbon atom of the aldehyde, making the cyclization of 2 -hydroxy-chalcone to flavanone difficult. Deactivation of the catalyst was not observed in the presence of moderate amounts of organic acids, such as benzoic, acrylic, or trichloroacetic acid. 

Finally, one must consider the possibility of an involatile residue being formed by one or more of the atomic species present in the molecular gas, e.g., adsorbed carbon from CF. Unless this residue is removed by some mechanism (step 5), it will terminate the etching reaction. Electron and ion bombardment could enhance residue removal by many of the same mechanisms mentioned above in connection with steps 2-4. 

This local adsorption geometry for formate on Cu(100) and Cu(110), with the molecular plane perpendicular to the surface and bonding through the two carboxylate atoms in near-atop sites, is also seen in other simple carboxylate species adsorbed on Cu(110), notably acetate (CH3COO—) [103] and benzoate (CgFIjCOO—) [104] formed, respectively, by exposure to acetic acid and benzoic acid. Relatively recent X-ray spectroscopy measurements combined with theoretical calculations provide further information on the bonding of formate and acetate on Cu(110) [105]. 

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