Heterogeneous kinetic studies of the hydrogen peroxide decomposition with some transition metal-heterocyclic complexes

The heterocyclic compounds piperidine (Pip), piperazine (Pz), morpholine (M orph), and N-methyl piperazine (N-MPz) were used as ligands to form transit ion metal complexes with Ni(lf), Cu(II), and Co(II) ions. These complexes w ere supported on Dowex-50W resin so as to form new potential active catalys ts for H2O2 decomposition in an aqueous medium, In all cases the reaction s howed a first-order kinetics with respect to H2O2 concentration, except wit h Co(II) complexes, the reaction showed a second-order kinetics with 2% div inyl benzene (DVB) (50-100 mesh and 200-400 mesh). The rate constant k (per gram dry resin) was evaluated with a resin of cross-linkage 2 and 8% DVB ( 50-100 mesh) and 2% DVB (200-400 mesh) over temperature range 25-40 degrees C. With a given resin cross-linkage, the rate constant has the following or der: Ni(II) complexes < Co(II) complexes < Cu(II) complexes. With Pz ligand , k increased in the following sequence: Ni(II) complexes < Cu(Il) complexe s < Co(II) complexes, The reaction mechanisms of the fist- and second-order kinetics were discussed and the activation parameters were deduced. <(c)> 2001 John Wiley & Sons, Inc.