Asymmetrical Concentration Fluctuations in the Autocatalytic Bromate-Bromide Catalyst Reaction and in the Oscillatory Belousov-Zhabotinsky Reaction in Closed Reactor: Stirring Effects

Abstract

with which volatile intermediates, such as ~~ygen~~~.~~~.~~ and lSb are transferred between the reactionary mixture and atmosphere; by the absorption of intermediates, i.e., bromine, onto the hydrophobic walls of the reactor, &-electrode, or ~tirrer;?~ in the case of a continuously stirred tank reactor (CSTR), by the macroheterogeneities appearing with incomplete mixing of the feed streams.'?.''.'hh.?4,.76 However, not all the stirring effects observed may be explained by these rather plain reasons. Some authors suggest that the stirring effect may be caused by the concentration fluctuations resulting from the interaction between fast chemical reactions and turbulent transport of substances.' '.'hc.d.i8-2125a These concentration fluctuations were recorded by Menzinger et a1.'6a.c with the aid of the Pt-microelectrodes. One of the most vivid manifestation of the stirring effect is an increase in the induction period TInd of the autocatalytic reactions with more intensive stirring. This is observed for the Briggs-Rauscher (BR) reaction,?Ia the chlorite-iodide and the chlorite-thiosulfate reaction.>Ob A similar phenomenon is also observed for the Belousov-Zhabotinsky (BZ) reaction, where a growth in stirring intensity leads to an increase in the oscillation peri~d.'~~.'~,'~ .~' Earlier,2'a.h we have discovered the effect of stirring on the induction period T,,,d of the autocatalytic reaction of iodide and iodine production in the BR reaction under batch conditions. As the stirring rate grows, the period Tind increases in a S-like manner. Special experiments showed', that the stirring effect is not concerned with iodine sorption on solid surfaces, with macroheterogeneities that are likely to occur as a result of nonuniform irradiation of the reactor, and with an oxygen and