Oscillating Bromate Oxidative Reactions

Zhabotinsky, A. M.

doi:10.1002/bbpc.19800840403

Cited by 24 publications

(2 citation statements)

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“…The occurrence of oscillatory phenomena in the systems with chemical reaction has been observed since the first half of the 19th century. − The first reports on the oscillatory kinetics of heterogeneous catalytic reactions appeared in the 1970s . The oxidation reaction of CO with oxygen is one of the most intensively studied processes involving heterogeneous catalysts. − Ertl, ,− when researching surface reactions, observed oscillations in the system of CO + O 2 /Pt and NO + CO/Pt.…”

Section: Introductionmentioning

confidence: 99%

Oscillatory Kinetics in the Process of Reduction of Nanocrystalline Iron Nitride γ′-Fe₄N

2017

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The kinetics of the reduction of nanocrystalline γ′-iron nitride to α-iron in mixtures of nitrogen and hydrogen of different hydrogen concentration was studied. Kinetic measurements were carried out in a differential chemical reactor with a thermogravimetric system for measuring the weight of a sample and an analyzer of hydrogen at 400 °C and at atmospheric pressure. The occurrence of cyclic changes in the rate of chemical reaction in a solid phase has been observed. Such an oscillatory phenomenon was not observed so far in the reaction between gases and a solid with phase transition in a solid phase, which results in a solid products. The mechanism of the observed phenomenon is explained, taking into account processes occurring in the volume of the solid phase. The oscillatory rate changes of the described processes prove a nonmonotonic coverage degree of the surface with nitrogen, which is caused by a step change in the free enthalpy of segregation of nitrogen in the reduction of γ′-Fe4N nitride. On the basis of model calculations the changes of free enthalpy of segregation during reduction of nitrides have been specified, and modification of the Fowler–Guggenheim equation has been proposed.

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Section: Introductionmentioning

confidence: 99%

Oscillatory Kinetics in the Process of Reduction of Nanocrystalline Iron Nitride γ′-Fe₄N

2017

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“…Experimental observations on oscillatory kinetics have been made with quite different systems, first with electrochemical reactions [3] and later quite extensively in homogeneous solution with the famous Belousov-Zhabotinsky (BZ) reaction and related systems [4,5]. In heterogeneous catalysis, rate oscillations were first reported around 1970 by Wicke and co-workers for the oxidation of carbon monoxide on supported platinum catalysts [6,7].…”

Section: Introductionmentioning

confidence: 99%

Non‐Linear Dynamics: Oscillatory Kinetics and Spatio‐Temporal Pattern Formation

Ertl

2008

Handbook of Heterogeneous Catalysis

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The rate of a catalytic reaction is governed by the underlying mechanism, i.e. the sequence of elementary reaction steps, and depends on the external control parameters such as the concentrations (= partial pressures) p j of educt and product species and temperature T, if transport processes are excluded in this context. More specifically, usually the adsorbed species are assumed to be randomly distributed over the surface, and their concentrations (= coverages) θ i are described within a mean-field approximation so that the reaction rate (= number of molecules r formed per unit time, dn r /dt t ) is given by dn r dt = f θ i , T ( ) (1) whereby the coverages θ i are in turn determined by a set of differential equations (modeling the individual steps of adsorption, desorption and surface reaction) of the typeProper treatment then requires that additional constraints given by heat and mass balance are taken into consideration.Under flow conditions with the external control parameters being kept fixed, usually the reaction proceeds at steady state with constant rate, i.e., dn r /dt = constant and dθ i /dt = 0. Due to the nonlinear character of the quoted differential equations, this has, however, not necessarily to be the case; the kinetics may -for certain ranges of parameters -become oscillatory or even irregular (chaotic). Such systems are typically far away from equilibrium, and (i) By far the most detailed insights into the underlying mechanisms and the general phenomenology of spatio-temporal self-organization were obtained in studies with well-defined single crystal surfaces by applying the arsenal of modern surface physical methods.(ii) Single crystal studies are usually conducted with bulk samples under low pressure conditions (≤ 10 -4 mbar)where the temperature changes associated with varying reaction rate are negligible. In addition, the mean-free path of gaseous molecules is comparable or even larger than the dimensions of the reaction vessel, which is operated as a continuous flow reactor. Hence, concentration gradients in the gas phase are practically instantaneously (≤ 10 -3 s)transmitted. Analysis of such experiments is thus appreciably simplified.(iii) Experiments with polycrystalline, i.e. "real", catalysts are usually conducted at elevated partial pressures (≥ 1 mbar) under which the heat released by the reaction may lead to noticeable temperature variations. The resulting thermokinetic effects may become dominating, so that even the nonuniformity of the surface chemistry is masked and quite novel phenomena may arise. Ideally, the reaction is conducted in a way, which may be described by a continuously stirred tank reactor (CSTR), i.e., perfect mixing ensures that the concentrations are everywhere identical.However, frequently a concentration profile exists along the reactor, which is hence rather of the plug-flow type. It is thus evident that heat and mass transfer limitations may play important roles with such systems.Generally, an extended system such as a single crystal surface, or even more ...

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Oscillatory Kinetics and Nonlinear Dynamics

Ertl

2009

Reactions at Solid Surfaces

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Oscillating Bromate Oxidative Reactions

Cited by 24 publications

References 45 publications

Oscillatory Kinetics in the Process of Reduction of Nanocrystalline Iron Nitride γ′-Fe₄N

Oscillatory Kinetics in the Process of Reduction of Nanocrystalline Iron Nitride γ′-Fe₄N

Non‐Linear Dynamics: Oscillatory Kinetics and Spatio‐Temporal Pattern Formation

Oscillatory Kinetics and Nonlinear Dynamics

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Oscillating Bromate Oxidative Reactions

Cited by 24 publications

References 45 publications

Oscillatory Kinetics in the Process of Reduction of Nanocrystalline Iron Nitride γ′-Fe4N

Oscillatory Kinetics in the Process of Reduction of Nanocrystalline Iron Nitride γ′-Fe4N

Non‐Linear Dynamics: Oscillatory Kinetics and Spatio‐Temporal Pattern Formation

Oscillatory Kinetics and Nonlinear Dynamics

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Oscillatory Kinetics in the Process of Reduction of Nanocrystalline Iron Nitride γ′-Fe₄N

Oscillatory Kinetics in the Process of Reduction of Nanocrystalline Iron Nitride γ′-Fe₄N