Chemical reaction wavefronts

This chapter deals principally with travelling wavefronts of chemical reactions of uniform speed and constant concentration profile but also considers pulses and periodic wave trains. Isothermal cubic autocatalysis offers deep insights into the phenomenon as a whole. After careful study the reader should be able to ... 

Professor Eyring and associates also introduced novel considerations concerning the relationship between the shape of the detonation wavefront and the rate of chemical reaction in the supporting reaction zone. While the predictions of the curved front theory turned out to be incorrect, it may yet point the direction of the correct answer because the discrepancy probably lies only in the basic assumptions, not in the fundamental character of the theory. 

The behaviour we are expecting to emerge from this physico-chemical model is that of a steady wave of reaction moving from left to right in Fig. 11.2 into the region of unreacted A. By steady, we really mean that the wavefront should maintain its shape as it moves with a constant speed. It is this shape and speed which we seek to determine (and express in terms of the rate constant, diffusion coefficient, etc.). 

Fiolitakis, E., Hoffmann, U., and Hoffmann, H. Application of wavefront analysis for kinetic investigation of water-gas shift reaction. Chemical Engineering Science, 1980, 35, 1021. 

Swinney and coworkers developed the continuously fed unstirred reactor (CFUR) in 1987 (Tam et al., 1988a). It consists of a gel that is in diffusive contact with an input from the CSTR, as shown in Figure 3.9. The gel prevents convection, and the CSTR keeps the system away from equilibrium. With this device, transitions between well-defined patterns can be studied. The CFUR does for the study of pattern formation and chemical waves what the CSTR did for oscillating reactions. If the gel is in the shape of a ring (an annular gel reactor), then, with special initiation conditions, pinwheels of wavefronts chasing each other can be created (Noszticzius et al., 1987). As we will see in Chapter 14, gel reactors proved essential for the discovery of Turing patterns. 

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