Evaluated Kinetic Data for Combustion Modeling. Supplement I (original) (raw)
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The kinetics of consecutive reactions
The complete solution of the matrix equation giving the concentrations with time of the constituents of a three-stage, consecutive reaction sequence is presented.
Introduction to Chemical Kinetics
Springer eBooks, 2017
After introducing the basis of the Arrhenius equation and its relationship to transition-state theory, forms of global chemical kinetic models are summarized, including shrinking core and pseudo nth-order reactions; sigmoidal reactions such as sequential, random scission, autocatalytic, logistic, and nucleation-growth model; and distributed reactivity models, including continuous and discrete activation energy distribution models. Isoconversional and model fitting methods for deriving chemical kinetic models are described, including how to use simple kinetic analyses to derive initial guesses for nonlinear regression of complex models. Common errors that lead to erroneous Arrhenius parameters are outlined.
The impact of the rate coefficient over the reaction mechanism
Applied Nanoscience, 2020
Mathematically, complex chemical reactions can be simplified by "model reduction," that is, the rigorous way of approximating and representing a complex model in simplified form. Furthermore, to reduce the dimension of the reaction mechanism, there are different available model reduction techniques (MRT). Without losing the essential information of the system, we have reduced the higher-dimension manifold to low-dimension manifold using spectral quasi equilibrium manifold (SQEM). Near the equilibrium point for different values of rate constant, the solution trajectories of reacting species are examined. The possible approaches to their solution and key problems are based on the Horiuti's rules and their slow invariants. The characteristic properties of nodes and trees of reaction mechanisms are addressed with the graph theory. The impact of the rate coefficient over the equilibrium of the system has been measured. The numerical approximations have been measured using SQEM with MATLAB and the model is analyzed graphically.
The Journal of Chemical Physics, 2010
The applicability of the Encounter Theory ͑ET͒ ͑the prototype of the Collision Theory͒ concepts for widely occurring diffusion assisted irreversible bulk reaction A + B → C ͑for example, radical reaction͒ in dilute solutions with arbitrary ratio of initial concentrations of reactants has been treated theoretically with modern many-particle method for the derivation of non-Markovian binary kinetic equations. The method shows that, just as in the reaction A + A → C considered earlier, the agreement with the Encounter Theory is observed when the familiar Integral Encounter Theory is used which is just a step in the derivation of kinetic equations in the framework of the method employed. It allows for two-particle correlations only, and fails to consider the correlation of reactant simultaneously with a partner and with a reactant in the bulk. However, the next step leading to the Modified Encounter Theory under reduction of equations to a regular form both extends the time applicability interval of ET homogeneous rate equation ͑as for reactions proceeding in excess of one of the reactants͒, and yields the inhomogeneous equation of the Generalized Encounter Theory ͑GET͒ that reveals macroscopic correlations induced by the encounters in a reservoir of free walks in full agreement with physical considerations. This means that the encounters of reactants in solution are correlated at rather large time interval of the reaction course. However, unlike the reaction A + A → C of identical reactants, the reaction A + B → C accumulation of the above macroscopic correlations ͑even with the initial concentrations of reactants being equal͒ proceeds much slower. Another distinction is that for the reaction A + A → C the long-term behavior of ET and GET kinetics is the same, while in the reaction A + B → C these kinetics behave differently. It is of interest that just taking account of the above macroscopic correlations in the reaction A + B → C ͑in GET͒ results in the universal character of the long-term behavior of the kinetics for the case of equal initial concentrations of reactants and that where one of the reactants is in excess. This is more natural from the point of view of the reaction course on the encounters of reactants in solutions.
Basic Concepts in Chemical Kinetics: Molecular Interpretations of Kinetic Phenomena 4.0 INTRODUCTION
In this chapter we treat the descriptions of the molecular events that lead to the kinetic phenomena that one observes in the laboratory. These events are referred to as the mechanism of the reaction. We begin with definitions of the various terms that are basic to the concept of reaction mechanisms, indicate how elementary events may be combined to yield a description that is consistent with observed macroscopic phenomena, and discuss some of the techniques that may be used to elucidate the mechanism of a reaction. Finally, two basic molecular theories of chemical kinetics are discussed: the kinetic theory of gases and transition-state theory. The determination of a reaction mechanism is a much more complex problem than that of obtaining an accurate rate expression, and the well-educated chemical engineer should have a knowledge of and an appreciation for some of the techniques used in such studies. There are at least two levels of sophistication at which one may approach the problem of providing a molecular description of the phenomena that occur during the course of a chemical reaction. At the first level the sequence of molecular events is described in terms of the number and type of molecules and molecular fragments that come together and react in the various steps. The second level of description contains all of the elements of the first but goes beyond it to treat the geometric and electronic configurations of the various species during the different stages of the reaction sequence. For this book, the first level of description is adequate. The second level is more appropriate for study in courses involving physical organic chemistry or advanced physical chemistry.
Non-equilibrium reaction rates and non-equilibrium effects in chemical kinetics
Journal of Physics: Conference Series
Non-equilibrium effects of different nature and their impact on the reaction and relaxation rates of the reacting gas mixture are considered. Expression for the dissociation rate is obtained employing the asymptotic method of solving Boltzmann equation, developed in the previous papers (Kolesnichenko, Gorbachev, 2010, 2013, Gorbachev 2016). Application of the projection method for solving the integral equations for zeroth-order corrections to quasiequilibrium distributions is examined. Possibilities of simplifying of the expressions for reaction rates are discussed.