Auto-oscillating reactions

Entropy, Entropy Production, Auto Catalysis and Oscillating Reactions 69... 

Example 12 The simplest system with time fading auto oscillations the scheme with an autocatalytic reaction and one "buffer" intermediate... 

Belyaev, et al. studied the catalytic oxidation of hydrogen, and found that the reactants act on the catalyst. This effect may be regarded as feedback. Several stationary states were found for the catalytic hydrogen oxidation reactions on nickel and for the reaction of CO with H. Belyaev et al. found stable auto-oscillations of the hydrogen oxidation rate on nickel foil under isothermal conditions. See Fig. III.16. 

An auto-catalytic reaction is one in which it is necessary to have reagent X to supply more product X. Auto-catalytic behavior is a imiversal characteristic observed in all oscillating chemical and biochemical reactions. It is the simplest chemical reaction to show instabilities. One auto-catalytic step is necessary to obtain instabilities, as shown by de Bonder, Onsager, and later by Prigogine, in order to fight against the second principle, and to achieve oixier and autoorganization. 

Recently there has been an increasing interest in self-oscillatory phenomena and also in formation of spatio-temporal structure, accompanied by the rapid development of theory concerning dynamics of such systems under nonlinear, nonequilibrium conditions. The discovery of model chemical reactions to produce self-oscillations and spatio-temporal structures has accelerated the studies on nonlinear dynamics in chemistry. The Belousov-Zhabotinskii(B-Z) reaction is the most famous among such types of oscillatory chemical reactions, and has been studied most frequently during the past couple of decades [1,2]. The B-Z reaction has attracted much interest from scientists with various discipline, because in this reaction, the rhythmic change between oxidation and reduction states can be easily observed in a test tube. As the reproducibility of the amplitude, period and some other experimental measures is rather high under a found condition, the mechanism of the B-Z reaction has been almost fully understood until now. The most important step in the induction of oscillations is the existence of auto-catalytic process in the reaction network. 

Continuous Multicomponent Distillation Column 501 Gas Separation by Membrane Permeation 475 Transport of Heavy Metals in Water and Sediment 565 Residence Time Distribution Studies 381 Nitrification in a Fluidised Bed Reactor 547 Conversion of Nitrobenzene to Aniline 329 Non-Ideal Stirred-Tank Reactor 374 Oscillating Tank Reactor Behaviour 290 Oxidation Reaction in an Aerated Tank 250 Classic Streeter-Phelps Oxygen Sag Curves 569 Auto-Refrigerated Reactor 295 Batch Reactor of Luyben 253 Reversible Reaction with Temperature Effects 305 Reversible Reaction with Variable Heat Capacities 299 Reaction with Integrated Extraction of Inhibitory Product 280... 

In the case of the nonisothermal first-order exothermic reaction heat is auto catalytic, for it raises the temperature and provokes an increase of reaction rate, yet is itself a product of the reaction. In the Gray-Scott scheme, B is plainly autocatalytic and its degeneration by the second reaction plays the role of the direct cooling in the non-isothermal case. This reaction appears in the chemical engineering literature in 1983,16 and is the keynote reaction in Gray and Scott s 1990 monograph on Chemical Oscillations and Instabilities.17 A justification of the autocatalytic mechanism in terms of successive bimolecular reactions is the subject of Chapter 12. 

The major characteristics of excitable media, such as oscillating chemical reactions, and some important concepts necessary for understanding their behaviour have been discussed. The capacity of Belousov-Zhabotinsky (BZ) reactions for spontaneous spatiotemporal auto-organization is described 289... 

This is a good classroom demonstration experiment. Hydroquinone stops the oscillations indicating the important role played by the free radicals. In such reactions, auto catalytic production CgHjCHO or CH3CHO has been envisaged as it happens in gas... 

The Belousov-Zhabotinsky (BZ) system is a methodically characterized chemical oscillation and provides an archetype scheme for smdy of wide ranges of patterning features in oscillatory chemical reactions [47-53]. This consists of bromination reaction initially and auto-oxidation of organic substrates is takes place in sequential processes by bromate ions. Overall, the reaction is catalyzed by redox catalysts in a concentrated water-acidic solution. 

The N2O decomposition reaction is especially interesting because under particular conditions the reaction can be induced to oscillate (see Fig. 4.28l l). If non-isothermal effects can be excluded, this implies the presence of an auto-catalytic elementary reaction step in the overall catalytic reaction cycle (see Chapter 8). In this case, the auto-catalysis results from N2O decomposition catalyzed by both mono-center and bi-center iron complexes. 

Stockmann, T.J., Nol, J.M., Ristori, S., Combellas, C., Abou-Hassan, A., Rossi, F., Kanoufi, F. Scanning electrochemical microscopy of Belousov-Zhabotinsky reaction how confined oscillations reveal short lived radicals and auto-catalytic species. Anal. Chem. 87(19), 9621-9630 (2015)... 

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