Hydrogen peroxide, rate decomposition

The rates for benzaldehyde oxidation to benzoic acid at 20 C are an order of magnitude lower than the hydrogen peroxide decomposition rates on these same catalysts for Ni/Al and Cu/Al calcined precipitates and provided only modest increases for the systems prepared in the presence of oxalic acid (Fig. 3). 

As the temperature is increased through the NTC zone, the contribution of alkylperoxy radicals falls. Littie alkyl hydroperoxide is made and hydrogen peroxide decomposition makes a greater contribution to radical generation. Eventually the rate goes through a minimum. At this point, reaction 2 is highly displaced to the left and alkyl radicals are the dominant radical species. 

The mechanism and rate of hydrogen peroxide decomposition depend on many factors, including temperature, pH, presence or absence of a catalyst (7—10), such as metal ions, oxides, and hydroxides etc. Some common metal ions that actively support homogeneous catalysis of the decomposition include ferrous, ferric, cuprous, cupric, chromate, dichromate, molybdate, tungstate, and vanadate. For combinations, such as iron and... 

The parameter most commonly monitored in this research is the extent of hydrogen peroxide decomposition. Measurement of tensile strength and/or the degree of polymerisation can be useful indicators of fibre damage. The effect of iron(III) ion concentration in accelerating the rate of peroxide decomposition is shown in Figure 10.23,... 

Figure 10.23 Effect of Fe(m) ion concentration on rate of hydrogen peroxide decomposition in absence of substrate [237]. Initial concentration 2.9 g/l H202, Sodium silicate 5 g/l, Magnesium sulphate 0.2 g/l, 95 °C, pH 12...

The total decomposition of hydrogen peroxide by the action of hydrogen ions was measured iodometrically in the absence of oxygen. The rate of hydrogen peroxide decomposition was found to be... 

In this connection it is important to recall the dependency of the degradation rate of hydrogen peroxide, r(-H202), on the absorbed photon flow Op (Gmelin, 1966). In addition, the quantum yield of H2O2 photolysis is a discrete function of Op (Lunak and Sedlak, 1992, Gmelin, 1966). It was demonstrated that the rate of hydrogen peroxide decomposition at low incident photon flows (Op <10 photons s ) can be described by Eq. 6-11 and at Op above this value Eq. 6-12 is valid. 

Studies of the chloride ion reaction required careful attention to impurities which at first gave rise to rates of hydrogen peroxide decomposition comparable to those under study. The reaction obeys the rate law... 

Determine catalase activity by measuring the rate of hydrogen peroxide decomposition. 

FIGURE 13.7 The rate of hydrogen peroxide decomposition can be measured with a manometer, which shows the increase in the oxygen gas pressure with time. 

It was first established by von Bertalan (40) that the rate of hydrogen peroxide decomposition in acid solution containing ferric ions is given by -d[H,04]Aft = fcc[Fe+++][H,Oj]/[H+] (c)... 

It is of interest to link ki to the rate of hydrogen peroxide decomposition. As shown in Figure 17.5, for a constant pH, the rate of oxidation correlates well with the rate of H2O2 decomposition. This observation is consistent with the idea of the presence of two channels for oxidation involving oxygen, and hydrogen peroxide as the second electron acceptor. The total rate of methyl viologen oxidation is the sum of the reaction rates in these two channels ... 

Fig. 5. Influence of addition of mixed complexes of Cu(II), Fe(IIl) and polyvinyl alcohol (PVA) on the rate of hydrogen peroxide decomposition (complex] = 2-10" mol/l ...

The effect of the initial substrate concentration on the initial reaction rate of hydrogen peroxide decomposition was studied over I-IO -2 10 mol/l range. For Cu complexes in the Fp-lg [S]q coordinates, the curve has the shape of an asymmetrical bell (Fig. 8, curve 1). This is characteristic of reactions involving enzymes whenever intermediate enzyme-substrate complexes of ES and S2-type form in the following reaction scheme ... 

An increase in the pH of the medium leads to an increase in the rate of hydrogen peroxide decomposition (Fig. 9). The effect that the pH has on the reaction rate is attributed to several processes occurring in the catalytic system. On the one hand, the change in the concentration of catalytically active centres occurs through the rear-... 

As the rate of hydrogen peroxide decomposition is higher in reaction (8.3c) than in reaction... 

The proposed model is based on the liquid-phase reactions the rates of escape of volatile species and gaseous O2 and I2 from the system are not considered. There is no direct autocatalytic or autoinhibition step of the form A -hxB (x + 1)B. The feedback is an intrinsic part of the model as a result of mutual combinations between reactions. Moreover, this model has all characteristics necessary to explain the considered catalytic hydrogen peroxide decomposition as one complex nonlinear process having a region of multistability wherein the different dynamic states from simple oscillatory to complex ones and chaos are found. 

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