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Abstract  

The example of the sequence of reactions

\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $${\text{A}}\xrightarrow{{k_1 }}{\text{B}}\xrightarrow{{k_2 }}{\text{C}}$$ \end{document}
and the steady-state approximation are used to present a demonstration of the fact that the evolution of the reaction rates under non-isothermal conditions depends on the ratio of the activation energies and on the heating rate. At the same time, it is shown that, under isothermal conditions, the ratio of the activation energies plays no role.

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Abstract  

The authors continue their considerations concerning the validity of the steady-state approximation in non-isothermal kinetics. A sequence of two first-order consecutive reactions with an active intermediate was subjected to kinetic analysis by numerical solution of the corresponding differential kinetic equations for a number of particular cases. The results demonstrated that the rate of change of concentration of the active intermediate is negligibly small if the assumption made in the isothermal case is also accepted for the non-isothermal case, i.e. k 2(T(t))>> k 1(T(t)).

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Abstract  

The paper investigates the validity of steady-state approximation for the case of constant rate thermal analysis experiments. It is shown that the approximation holds for the experiments run with a controlled rate of either the decomposition of the compound, or the production of gas.

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Abstract  

By kinetic modelling of the possible reactions of diphenylamine (DPA) and its nitrated consecutive products used to stabilize cellulose nitrate (CN), one can get reactivities for the nitrated DPA compounds for the situation inside a real CN formulation and therewith determine their stabilizing contribution. Concentration data of DPA and seven of its consecutive products have been determined by HPLC from isothermal ageing of a CN formulation at temperatures between 65 and 90°C for up to 344 days. A comparison between the modelling presented and modellings published in the literature using the steady-state approximation is made. The steady-state approximation oversimplifies the stabilizer reaction behaviour in a CN formulation. From the applied modelling the question about N—NO—DPA as a key intermediate can be answered.

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Reaction Kinetics, Mechanisms and Catalysis
Authors: Frederico A. D. Araújo, Sonia V. Pereira, Deivson C. S. Sales, A. R. Schuler, and Cesar A. M. Abreu

A alcohol, C catalyst, FA fatty acid, E ester The intermediate complexes were quickly formed and consumed; therefore, steady state approximations were useful. Considering this condition for the

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is assumed to be much faster than the second one, so the intermediate M is in equilibrium with the reactant A and B at any time. By the steady-state approximation, the concentration of M can be represented as: (3) (4) The rate of formation

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mathematical description expressed in Eqs. 4 – 7 . (4) (5) (6) (7) Under continuous irradiation, the concentration of excited species [TiO 2 ]* is considered constant (steady-state approximation) and its derivative in Eq. 5 equals to zero

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