STUDIES ON NONLINEAR KINETICS FOR THIOURE A OXIDATION - H2O2-SC(NH2)(2)-CU2+ REACTION SYSTEM

The reaction between hydrogen peroxide and thiourea in acidic medium ( HClO4) catalyzed by Cu2+ has been studied both in a closed (batch) sys tem and in a flow reactor (CSTR), A new thiourea oscillator has been f ound. Under the batch condition the reaction displays single-peak osci llation behavior in the redox potential, Amplitude and induction time of the reaction vary as the initial reactant concentrations and the te mperature of reaction, This induction time could be reduced by higher initial hydrogen peroxide concentrations and lower initial thiourea co ncentrations. In the CSTR, the reaction system displays sustained peri odic oscillations in the potentials of Pt electrode and Cu2+-selective electrode and pH electrode, As the flow rate is decreased, complex os cillations appear, The oscillatory region is shown in phase diagrams. The oscillation behavior is related to [H2O2]/[SC(NH2)(2)] ratio. No b istability is observed in the system.