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Kinetics and Mechanisms of Heterogeneously Catalyzed Reactions

Kinetics and Mechanisms of Heterogeneously Catalyzed Reactions 103 Table 5-2 Comparison of physisorption and chemisorption... [Pg.103]

Vibrational spectroscopic studies of heterogeneously catalyzed reactions refer to experiments with low area metals in ultra high vacuum (UHV) as well as experiments with high area, supported metal oxides over wide ranges of pressure, temperature and composition [1]. There is clearly a need for this experimental diversity. UHV studies lead to a better understanding of the fundamental structure and chemistry of the surface-adsorbate system. Supported metals and metal oxides are utilized in a variety of reactions. Their study leads to a better understanding of the chemistry, kinetics and mechanisms in the reaction. Unfortunately, the most widely used technique for determining adsorbate molecular structure in UHV,... [Pg.435]

In a few cases, the kinetics of heterogenous catalyzed reactions is based on a complete knowledge of the underlying reaction mechanisms. Generally, the kinetics of many commercially important reactions are derived from experimental investigations and are often based on simplified reaction models. [Pg.50]

The observed kinetics of heterogeneously catalyzed reactions are affected by various phenomena at different scales. For a detailed investigation of a reaction mechanism the effects of mass and heat transfer limitations at the catalyst scale should be negligible. Also no deviations from the ideal plug flow or perfectly mixed flow pattern should occur at the reactor scale. [Pg.1362]

See the general references in the Introduction, and some more-specialized books [1-25]. Some articles in journals discuss synthetic catalysts for the photooxidation of water to oxygen [26] kinetics and mechanisms of metal-02 complexes [27] d-block-catalyzed oxidation of sulfur(IV), especially in the atmosphere [28] various metal-02 complexes [29] mainly mono- and poly-selenide and telluride complexes with d-block elements [30] heterogeneous redox catalysts for oxygen release [31] the kinetics and equilibria of oxygen species and metal ions [32] thio- and seleno-complexes of V, Mb, Ta, Mo, W and Re [33] and homonu-clear sulfur species, not emphasizing aqueous reactions [34]. [Pg.442]

Predictability of activity, selectivity, and stability based on known structures of catalysts can be considered the main aim of the theoretical approaches applied to catalysis. Here, for a particular class of heterogeneous catalysts, namely, acidic zeolites, we present the theoretical approaches that are available to accomplish this goal, which lead to a better understanding of molecular motion within the zeolitic micropores and the reactivity of zeolitic protons. It is not our aim to introduce the methods as such, since introductory treatments on those can be found elsewhere. Rather we focus on their application and use to solve questions on mechanisms and reactivity in zeolites. The discussion is focused on an understanding of the kinetics of zeolite-catalyzed reactions. [Pg.398]

We are concerned with the kinetics of zeolite-catalyzed reactions. Emphasis is put on the use of the results of simulation studies for the prediction of the overall kinetics of a heterogeneous catalytic reaction. As we will see later, whereas for an analysis of reactivity the results of mechanistic quantum-chemical studies are relevant, to study adsorption and diffusion, statistical mechanical techniques that are based on empirical potentials have to be used. [Pg.399]

In this chapter we extend our treatment of mechanisms for metal-catalyzed reactions in the vapor phase to heterogeneous catalytic reactions carried out in aqueous media and electrocatalytic reactions. More specifically, we discuss what is known about the wa-ter/metal interface, its reactivity, and the influence of the aqueous phase on elementary surface processes including adsorption, reaction, diffusion and desorption and sofution-phase kinetic processes. We advance these ideas into the discussion of the mechanisms... [Pg.267]

For nonelementary reactions, the rate expression is not at all self-evident. For such reactions, the concentration dependence of reaction velocities can be determined empirically from experimental data. A more sustainable way is to derive the rate expression as a function of concentration R = /(c) starting from molecular mechanisms. This subject is treated in detail in specialized literatures [1-5], but the methods for nonelementary kinetics are summarized in the next section. Typical rate expressions for common homogeneously and heterogeneously catalyzed reactions are provided in Table 2.1. In reactor modeling, such expressions can be utilized in an operative manner, without penetrating their physical and chemical background. The estimation of numerical values of rate constants is in most cases based on experimental data. The procedure is described in detail in Appendices 9 and 10. [Pg.15]

Heterogeneously catalyzed reactions in open systems often exhibit steady-state hysteresis, complex self-generated oscillations and spatial instabilities. These are described by mathematical models which differ in their descriptions of the surface kinetic mechanism and of heat and mass transport processes. [Pg.35]

The analysis of Langmuir [/. Am. Chem. Soc. 40 1361 (1918)] and Hinshelwood (Kinetics of Chemical Change, Oxford, 1940) form the basis for the simplified treatment of kinetics on heterogeneous catalysts. For a solid catalyzed reaction between gas phase reactants A and B, the postulated mechanism consists of the following steps in series ... [Pg.16]


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And mechanism of reaction

Catalyzed reactions, mechanisms

Heterogeneous kinetics

Heterogeneous reaction

Heterogeneous reaction kinetics

Heterogeneous reactions mechanism

Heterogeneously catalyzed

Heterogeneously catalyzed reaction

Heterogenous Kinetics

Kinetic mechanism

Kinetic reaction mechanism

Kinetics and mechanism

Kinetics mechanisms

Kinetics of catalyzed reactions

Kinetics of heterogeneous reactions

Kinetics reaction mechanisms

Mechanical reaction kinetics

Mechanism of heterogeneous reactions

Mechanism of reactions catalyzed

Reaction heterogeneous reactions

Reaction mechanisms heterogenous

Reactions kinetics and mechanism

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