Langmuir—Hinshelwood mechanism, for

Solid-catalyzed 7eactioixs. Some Langmuir-Hinshelwood mechanisms for the reference reaction A -I- B R -I- S (see also Tables 7.2, 7.3) ... 

Solid-catalyzed reections, some Langmuir-Hinshelwood mechanisms for the referenca reaction A + B-> R + S. 

The synthesis of paratolunitrile (PTN) and terephtalonitrile (TPN) by reaction of paraxylene with nitrogen monoxide was studied over a series of aerogel chromium oxide alumina catalysts. The stabilization of the active phase was interpreted on the basis of Cr O support interactions. Kinetic studies show that the reaction follows a "redox" mechanism for the formation of PTN and a Langmuir Hinshelwood mechanism for the production of TPN. 

We will consider simple examples, i.e. the Eley-Rideal and Langmuir-Hinshelwood mechanisms for CO oxidation on Pt. Bipartite graphs corresponding to these mechanisms are represented in Fig. 3. In accordance with the general scheme, let us list segments, paths and cycles of these graphs. 

These results strongly suggest that the hydrogenation and oxidation of chemisorbed Q proceeds via a Langmuir-Hinshelwood mechanism. For the hydrogenation reaction, the following (possible) reactions may be written ... 

This concept was first mathematically developed by Clark and Bailey according to an exponential distribution of active centres with respect to adsorption energy. The Langmuir-Hinshelwood mechanism for adsorption and reaction was found to fit experimental results (ethylene polymerization over chromium oxide-silica-alumina catalyst) more closely than the Rideal mechanism. 

Bandyopadhyay, D. Ghosh, A. (1996). Validity of rate equation based on Langmuir-Hinshelwood mechanism for gasification of carbon - a reappraisal. 

Zhdan et al. ° have found an unreactive form of O on Ir(l 11) even at 1100 K, and have gone on to study the steady-state oxidation on this surface, establishing a Langmuir-Hinshelwood mechanism for reaction between chemisorbed O and chemisorbed CO. Two forms of adsorbed O on Ir(lll) have also been identified by Ivanov et al., only one of which is active in CO oxidation. 

Solid-catalyzed reactions, some Langmuir-HInshelwood mechanisms for the reference reaction A -1- B- R -f S. 

These kinetic observations indicate a competitive activation of the two reactants, leading to an inhibiting effect at high concentrations. The results can be interpreted in terms of a Langmuir - Hinshelwood mechanism for which the surface reaction takes place between thiophene and butyroyl chloride both adsorbed on identical active sites. 

Langmuir-Hinshelwood Mechanisms for Surface-Catalyzed Reactions... 

Consider the Langmuir-Hinshelwood mechanism for a dual-site ratecontrolling surface-catalyzed chemical reaction (A B C) and describe how Cl analysis of the initial rate of reaction shonld be modified if the chemical reaction is reversible, and the equilibrinm constant is known from thermodynamic data. The feed contains only reactant A. 

Figure4.11.5 (Pre)selection ofthe appropriate kinetic equation influence of total pressure and partial pressure of one reactant on initial rate of a heterogeneously catalyzed bimolecular gas reaction of A and B (a) Langmuir-Hinshelwood mechanism for variation of total pressure p (b) Eley-Rideal mechanism for variation ofp (c) Langmuir-Hinshelwood for variation of partial pressure of one ofthe adsorbed reactants (e.g., Pa) (d) Eley-Rideal mechanism for variation of partial pressure of adsorbed reactantA (p ) (e) Eley-Rideal mechanism for variation of partial pressure of reactant B (not adsorbed).

Fig. 1.6 Cartoons illustrating the (a) Eley-Rideal and (b) Langmuir-Hinshelwood mechanisms for reactions at surfaces...

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