Nonlinear phenomena in oscillatory systems of homogeneous reactions - experimental observations

An oscillating system of homogeneous chemical reactions (oxidation of malonic acid by bromate with ceric/cerous ion system as the catalyst) was followed experimentally in several reactor configurations, operated both as close and open systems. Characteristic nonlinear phenomena observed include: damped oscillations of concentrations of reaction components in a well stirred batch reactor, undampted oscillations and sudden changes of oscillatory behaviour (jump to a new steady state) in CSTR and interaction of oscillations in the two connected CSTRs. In a tubular reactor stationary and travelling concentration waves were observed. In the system of CSTR connected with a tubular reactor spreading of waves from CSTR to the tubular reactor, and vice versa was followed. In the flow through tubular reactor the formation of non-monotomic concentration profiles was measured, which were basically stationary with respect to changing flow-rate. The course of oscillations in CSTR was simulated on the basis of a semiempirical reaction kinetics model. An attempt to simulate quantitatively the behaviour of the distributed system with the common type of Fickian diffusion balance equations failed. Difficulties in the proper description of the transport of ions through the concentration gradient and the gradient of the electrical potential found in this system are discussed.