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Chemical Kinetics Reaction

Despite the strong biasing of reactions toward the energetically downhill direction, they cannot occur at infinite speed. Reaction rates are finite even if they are energetically downhill because  [Pg.48]

We depend on random thermal motions/vibrations to bring reactants together so that the bond-breaking and bond-making processes can occur. [Pg.48]

These factors limit the rate at which reactions can occur and furthermore help explain two fundamental principles of reactions kinetics (1) that reaction rates tend to be sensitive to the concentration of the reacting species and (2) that reaction rates tend to be highly sensitive to temperature. As the concentration of the reactants increases, the frequency with which they encounter one another increases proportionally. Likewise, as temperature increases, the random thermal motion and vibration of atoms increase, thereby increasing both the frequency with which the reactants can interact and the probability that the reactants can make it over the activation barrier to form products. As we will see in this chapter, these factors generally lead to a direct relationship between reaction rate and reactant concentration and an exponential increase in reaction rate with increasing temperature. [Pg.49]

While increasing temperature tends to increase reaction rates, increasing reaction complexity tends to decrease reaction rates. This third fundamental principle of reaction kinetics can also be understood from an atomic-level perspective of reaction processes. In general, as the number of reactant atoms or product atoms involved in a reaction increases, the likelihood that they can all converge at the same time and place in order to react decreases. This effect is usually captured in a term known as the order of the reaction. The order of a reaction has a direct impact on how the reaction kinetics are treated mathematically, with zero-order reactions being the simplest (both mechanistically and mathematically), followed by first-order reactions, second-order reactions, and so on. [Pg.49]

In the sections that follow, we will delve deeply into the atomistic world of reaction kinetics and learn how to predict the rates of a number of fairly simple zero, first, and second-order reaction processes. While this chapter will focus mostly on simple gas-phase chemical reaction processes, the principles learned here will apply just as well to the solid-state materials kinetic examples that we will confront later in the textbook. This is because bond-breaking and bond-forming processes are remarkably similar at the atomistic level whether they happen between molecules in the gas phase or between atoms in a solid. Thus, most reaction processes can be described using a common set of approaches. Toward the end of the chapter, in preparation for later solid-state applications of reaction kinetic principles, we will examine how reaction rates can be affected by a catalyst or a surface, and we will learn how to model several gas-solid surface reaction processes relevant to materials science and engineering. [Pg.50]


Flere, we shall concentrate on basic approaches which lie at the foundations of the most widely used models. Simplified collision theories for bimolecular reactions are frequently used for the interpretation of experimental gas-phase kinetic data. The general transition state theory of elementary reactions fomis the starting point of many more elaborate versions of quasi-equilibrium theories of chemical reaction kinetics [27, M, 37 and 38]. [Pg.774]

There are two main applications for such real-time analysis. The first is the detemiination of the chemical reaction kinetics. Wlien the sample temperature is ramped linearly with time, the data of thickness of fomied phase together with ramped temperature allows calculation of the complete reaction kinetics (that is, both the activation energy and tlie pre-exponential factor) from a single sample [6], instead of having to perfomi many different temperature ramps as is the usual case in differential themial analysis [7, 8, 9, 10 and H]. The second application is in detemiining the... [Pg.1835]

Ceramic—metal interfaces are generally formed at high temperatures. Diffusion and chemical reaction kinetics are faster at elevated temperatures. Knowledge of the chemical reaction products and, if possible, their properties are needed. It is therefore imperative to understand the thermodynamics and kinetics of reactions such that processing can be controlled and optimum properties obtained. [Pg.199]

Both the principles of chemical reaction kinetics and thermodynamic equilibrium are considered in choosing process conditions. Any complete rate equation for a reversible reaction involves the equilibrium constant, but quite often, complete rate equations are not readily available to the engineer. Thus, the engineer first must determine the temperature range in which the chemical reaction will proceed at a... [Pg.59]

This book is based on courses, which the authors have taught at Lyngby and Eindhoven for many years. For example. Chapters 1-3 form the basis for a mandatory course Kinetics and Catalysis presented in the second year of the Bachelor s curriculum at Eindhoven, while Chapters 4,5 and 8-10 formed the basis for an optional course Introduction to Catalysis. In Lyngby, Chapters 1-7 have been used for an optional course in Chemical Reaction Kinetics and Catalysis in the Master s curriculum. At the end of the book we have added a list of questions for every chapter. [Pg.466]

For this purpose, cylindrical channels have been assumed. In randomly packed fixed beds the porosity is about 0.4, from which the relationship dp = 2.25 d is obtained. Since the focus is on heterogeneously catalyzed gas-phase reactions, it is important to not only ensure comparable conditions from a hydrodynamic point of view, but also as far as chemical reaction kinetics is concerned. Therefore, it is assumed that both reactors contain the same amount of catalyst. [Pg.33]

The simple pore structure shown in Figure 2.69 allows the use of some simplified models for mass transfer in the porous medium coupled with chemical reaction kinetics. An overview of corresponding modeling approaches is given in [194]. The reaction-diffusion dynamics inside a pore can be approximated by a one-dimensional equation... [Pg.247]

Kuznetsov, A. M., Charge Transfer in Chemical Reaction Kinetics, Presses Polytechniques et Universitaires Romandes, Lausanne, Switzerland, 1997. [Pg.660]

Kuznetsov, A. M., Stochastic and Dynamic Views of Chemical Reaction Kinetics in Solutions, Presses Polytechniques et Universitaires Romandes, Lausanne, Switzerland, 1999. Kuznetsov, A. M., and J. Ulstrup, Electron Transfer in Chemistry and Biology, Wiley, Chichester, West Sussex, England, 1999. [Pg.660]

If the reactant solid is porous, the reactant fluid would diffuse into it while reacting with it on its path diffusion and chemical reaction would occur in parallel over a diffuse zone. The analysis of such a reaction system is normally more complex as compared to reaction systems involving nonporous solids. Here also it is important to assess the relative importance of chemical reaction kinetics and of mass and heat transport. [Pg.333]

This section contains a brief survey of NMR spectroscopic investigations of chemical reaction kinetics and mechanisms. One of the goals of reaction kinetics studies is to measure the rate of the reaction (or rate constant) - the rate at which the reactants are transformed into the products. Another goal is to determine the elementary steps that constitute a multi-step reaction. Finally, and perhaps the most important goal is to identify transitory intermediate species. NMR, in common with other spectroscopic techniques, is especially valuable in achieving this... [Pg.126]

One feature that distinguishes the education of the chemical engineer from that of other engineers is an exposure to the basic concepts of chemical reaction kinetics and chemical reactor design. This textbook provides a judicious introductory level overview of these subjects. Emphasis is placed on the aspects of chemical kinetics and material and energy balances that form the foundation for the practice of reactor design. [Pg.598]

Propagation problems. These problems are concerned with predicting the subsequent behavior of a system from a knowledge of the initial state. For this reason they are often called the transient (time-varying) or unsteady-state phenomena. Chemical engineering examples include the transient state of chemical reactions (kinetics), the propagation of pressure waves in a fluid, transient behavior of an adsorption column, and the rate of approach to equilibrium of a packed distillation column. [Pg.3]


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Basic Concepts in Chemical Kinetics—Determination of the Reaction Rate Expression

Chemical Reaction Rate Surface Kinetics

Chemical Reaction and Phase Transformation Kinetics in Solids

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Chemical kinetics

Chemical kinetics acid, base reactions

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Chemical kinetics of heterogeneous catalytic reactions

Chemical kinetics pseudo-first-order reactions

Chemical kinetics reaction order

Chemical kinetics reaction rates

Chemical kinetics second-order reactions

Chemical kinetics series reactions

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Chemical kinetics zero-order reactions

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Chemical reaction equilibrium/kinetic

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Chemical reaction kinetic models:

Chemical reaction kinetics activation theory)

Chemical reaction kinetics catalyst effects

Chemical reaction kinetics defined

Chemical reaction kinetics difference between heterogeneous

Chemical reaction kinetics difference between homogeneous

Chemical reaction kinetics first-order reactions

Chemical reaction kinetics incomplete reactions/equilibrium

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Chemical reaction kinetics reactions

Chemical reaction kinetics reactions

Chemical reaction kinetics second-order reactions

Chemical reaction kinetics temperature dependence

Chemical reaction kinetics zero-order reactions

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Chemical reaction rate theory, relaxation kinetics

Chemical reactions bimolecular, kinetics

Chemical reactions equilibrium kinetics

Chemical reactions kinetic activation

Chemical reactions kinetically-controlled

Chemical reactions, kinetics exponential temperature dependence

Chemical reactions, kinetics high-pressure limit

Chemical reactions, kinetics pressure effects

Chemical reactions, kinetics pressure-independent

Chemical reactions, kinetics rate coefficients

Chemical reactions, kinetics rate laws

Chemical reactions, kinetics recombination

Chemical reactions, kinetics temperature-dependent

Chemical reactions, kinetics thermal decomposition

Chemical reactors reaction kinetics

Example. Fitting kinetic parameters of a chemical reaction

First-order chemical kinetics parallel reaction

First-order chemical kinetics reaction control

First-order chemical kinetics series reaction

Formal Kinetics Description of Chemical Reactions

Fundamentals of Chemical Chain Reaction Kinetics

General Kinetic Rules for Chemical Reactions

Inclusion of a chemical reaction into kinetic theory

Kinetic Chemicals

Kinetic Factors in Pyrolytic Chemical Reactions

Kinetic Irreversibility of Chemical Reactions

Kinetic Isotope Effects on Chemical Reactions

Kinetic Studies chemical reactions, rate controlling

Kinetic modeling chemical reaction processes

Kinetics Rates and Mechanisms of Chemical Reactions

Kinetics and Chemical Reaction Engineering

Kinetics and Chemical Reaction Stoichiometry

Kinetics and Thermodynamics of Chemical Reactions

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Kinetics, chemical first-order reaction

Kinetics, chemical reaction mechanisms

Kinetics, chemical unimolecular reactions

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Reaction Rate Fundamentals (Chemical Kinetics)

Reaction homogeneous chemical kinetics

Reaction-diffusion systems generalized chemical kinetics

Reduction kinetics, solid-state chemical reactions

Reversible chemical reactions kinetics

Stochastic simulations of chemical reaction kinetics

Stoichiometry and Kinetics of Chemical Reactions

Surface Kinetics of Chemical Reactions

Surface chemical reactions kinetics

Surface chemistry Kinetics of heterogeneous chemical reaction

The kinetic theory applied to chemical reactions in solutions

Theoretical Studies on Mechanism and Kinetics of Atmospheric Chemical Reactions

Thermodynamic and kinetic characteristics of chemical reactions in solution

Transport and reaction in the light of chemical kinetics

W. Litz, Bench Scale Calorimetry in Chemical Reaction Kinetics

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