New Experimental and Computational Results on the Radical-Controlled Oscillating Belousov-Zhabotinsky Reaction

GP Misra
RP Washington
JA Pojman


New experimental results on the oscillatory dynamics of the radical-controlled Belousov-Zhabotinsky reaction (the Racz system) in a batch reactor are reported. The system exhibits oscillations with no induction period, a typical feature of the radical-controlled mechanism. However, in the presence of acetylacetone (CH2(COCH3)(2)), an induction period is observed before oscillations start, which increases with increasing acetylacetone concentration. There is a critical concentration of acetylacetone at which no oscillations occur. Quenching of radical-controlled oscillations is also observed at low and high malonic acid concentrations as well as at low and high sulfuric acid concentrations. An induction period is observed before the onset of radical-controlled oscillations at sulfuric acid concentrations greater than or equal to 5.5 M. The duration of radical-controlled oscillations reaches a maximum at an intermediate sulfuric acid concentration. Numerical simulations based on the Radicalator model predict limits of malonic acid and sulfuric acid concentration within which oscillations are observed. The Radicalator model with additional reactions involving (i) CH2(COCH3)(2) + Ce4+ --> (CH)-C-.(COCH3)(2), (ii) (CH)-C-.(COCH3)(2) + BrO2. --> products, and (iii) (CH)-C-.(COCH3)(2) + (CH)-C-.(COCH3)(2) --> products also predicts lengthening of induction period with the increase of acetylacetone concentration and suppression of oscillations at high acetylacetone concentration. Inclusion of the reaction between acetylacetone and HOBr had no effect.