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

Abstract

The heterocyclic compounds piperidine (Pip), piperazine (Pz), morpholine (Morph), and N-methyl piperazine (N-MPz) were used as ligands to form transition metal complexes with Ni(II), Cu(II), and Co(II) ions. These complexes were supported on Dowex-50W resin so as to form new potential active catalysts for H 2 O 2 decomposition in an aqueous medium. In all cases the reaction showed a first-order kinetics with respect to H 2 O 2 concentration, except with Co(II) complexes, the reaction showed a second-order kinetics with 2% divinyl 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 • C. With a given resin cross-linkage, the rate constant has the following order: Ni(II) complexes < Co(II) complexes < Cu(II) complexes. With Pz ligand, k increased in the following sequence: Ni(II) complexes < Cu(II) complexes < Co(II) complexes. The reaction mechanisms of the fi rst-and second-order kinetics were discussed and the activation parameters were deduced.

Catalytic activities of amino acid modified, starch‐grafted acrylamide for the decomposition of hydrogen peroxide

“…The increased reactivity of the glycine catalyst, compared with that of the other two, is probably due to (1) the increased loading of Fe III ions by the glycine‐modified graft in comparison with the other two systems, (2) the increased accessibility of H 2 O 2 to the reactive Fe III ‐glycine sites distributed throughout the polymer particles, and (3) the increased stability constant of the complex (a greater stability constant leading to a higher reaction rate) 26. This substrate accessibility is reduced, probably because of steric hindrance in the case of the large ligands β‐alanine and phenylalanine.…”

A mathematical model of the defence mechanism of a bombardier beetle

“…While there is little information available on the range of concentrations of the reactants, the products of the ESD-in particular, 1,4-benzoquinones and n-alkanesshow large variations [7], implying a potentially wide range of reactant concentrations. The chemical reaction parameter values-in particular, the reaction rate and the activation energy-are not known for any individual bombardier species, but the activation energy used here is within the range 30-60 J mol -1 reported for a range of catalysts [22].…”