Kinetics, catalytic hydrogenolysis

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... 

Catalytic hydrogenolysis (continued) M0O3-AI2O3 catalyst, 29 258-269 relative reactivity, 29 255-257 schematic model, 29 254 diphenylmethane kinetics, 29 241-243 reaction mechanism, 29 267 Catalytic oxidation,... 

Diphenylmethane catalytic hydrogenolysis kinetics, 29 241-243 reduction mechanism, 29 267 cyclization, 30 65 dehydrocyclization, 28 318 [(Diphenylphosphino)alkyl]phosphonates, 42 479... 

Diphenylmethane (DPM), the basic hydrocarbon of the diarylmethane series, is the most appropriate compound for studying the kinetics of the catalytic hydrogenolysis of diarylmethane. This study involved a CoO-M0O3-AI2O3 catalyst (4 wt % CoO, 12 wt % M0O3) (5i). 

D. The Kinetics and the Scheme of the Catalytic Hydrogenolysis of Asymmetric Diarylmethane... 

Table XV summarizes kinetic parameters for hydrogenolysis reactions of alkanes and cycloalkanes over film catalysts and over supported catalysts for which it can be reasonably assumed that reaction is confined to the metallic phase. These kinetic parameters refer to the overall reaction, i.e., to the rate of disappearance of the parent molecule. It will be evident from Table XV that the catalytic activity of a given metal with a given...

The activation of alkanes on transition metal surfaces is an important step in many catalytic reactions. Hydrogenolysis, steam reforming and isomerization of alkanes all involve alkane dissodation. Thus, much interest exists in the mechanistic and kinetic aspects of alkane dissociation. 

In this section we shall consider the results recorded in the literature that pertain to the structures of the adsorbed species. Kinetic or catalytic aspects, as could be relevant to hydrogenation, hydrogenolysis, or metathesis processes, will be treated in Part 11. Spectra of the much-investigated alkenes are discussed in detail in Part I. The spectra of the other principal types of hydrocarbon adsorbates, viz. alkynes, alkanes, cycloalkanes, and aromatics, will be analyzed in Part II. Most results are available for the type-molecules ethene, ethyne, ethane, and benzene as well as for the metals, Pt, Pd, Ni, Rh, and Ru. 

A close look at the hydrogenolysis reaction of the Cp2 SmCH(TMS)2 complex with H2Si(SiMe3)2 shows that the two compounds do not react directly. The kinetic profile shows an S-shape form with an induction time. This shape is consistent with a second-order autocatalytic mechanism in which the reaction is catalyzed by a product or an intermediate. Indeed, the induction period was completely eliminated by addition of catalytic amounts of H2, [Cp2 SmH]2, or of the complex [Cp2 Sm (p-H) (p-C CsMe SmCp ], which is a decomposition product of the [Cp2 SmH]2. Thus, two possible mechanistic pathways (Schemes 3 and 4) have been proposed to explain the hydrogenolysis reaction. 

In view of the accuracy of today s quantum chemical calculations, it is typically necessary to adjust the initial estimates of the potential energy surface to describe the observed kinetics of a catalytic process. Accordingly, the theoretical results presented in Table V provide only initial guesses for the entropies and enthalpies of the stable species and reactive intermediates involved in ethane hydrogenolysis on platinum. 

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