Abdel-Fattah M. Habib

The role of resin-amine transition metal complexes in hydrogen peroxide decomposition

Abstract Dowex-50W resin in the form of ethylamine- and dimethylamine-transition metal ion (Co II , Ni II , Mn II ) complexes have been used as potentially active catalysts for H 2 O 2 decomposition in an aqueous medium. The rate constant (per g of dry resin) was evaluated with a resin containing 8% divinylbenzene crosslinkage over the temperature range 25 – 40 °C. With both ligands the reaction rate was directly proportional to [H 2 O 2 ] for complexes with Co II and Ni II and to [H 2 O 2 ] 2 for Mn II complexes. Probable mechanisms for the reactions have been proposed. The activation energy with both ligands was found to increase in the following sequence: Ni II II II . The activation energies of the complexes with the Me 2 NH ligand were smaller than those with the EtNH 2 ligand. The change in the entropy of activation, the rate constant (per g of dry resin) and the probability of activated complex formation with the secondary amine (Me 2 NH)-transition metal complexes were smaller than those with the primary amine (EtNH 2 )-transition metal complexes. This is due to the steric effect of the methyl groups in the Me 2 NH ligand.

Role of resin-copper(II) complexes containing ethanolamines in hydrogen peroxide decomposition

SummaryDowex-50W resins in the form of mono (mea)-, di (dea)-and tri-ethanolamine (tea)-CuII complexes have been used as potentially active catalysts for H2O2 decomposition in an aqueous medium. The rate constant (per g of dry resin) was evaluated with resins containing 2,8 and 12% divinylbenzene (DVB) crosslinkage, over the temperature range 25–40°C. The reaction was first order with respect to [H2O2] with mea for 8 and 12% DVB (50–100 mesh), second order with mea for 2% DVB (50–100 and 200–400 mesh) and third order with dea and tea for 8% DVB (50–100 mesh). The value of the rate constant (per g of dry resin) of the mea-CuII/CoII binary system was compared with that of the mea-CuII/NiII binary system. With a given degree of resin crosslinkage the activation energy increased in the sequence mea < dea < tea, which is the inverse sequence of the basic strength of the free amines. The activation parameters were calculated. Probable mechanisms were proposed for the reaction with the three ethanolamines.

Ion exchangers as catalysts. II. Catalytic decomposition of hydrogen peroxide with resin-ethylenediamine-copper(II) complex ions

SummaryThe slow decomposition of H2O2 in the presence of Dowex-50 W resin in the form of an ethylenediaminecopper(II) complex ion in water is accompanied by an induction period. The reaction is first order with respect to [H2O2] and the rate constant (perg of dry resin) was deduced. Autocatalytic behaviour was found for the H2O2 decomposition with 2% crosslinked divinylbenzene. The induction period disappeared and the reaction rate increased when the decomposition was carried out with a resin in the form of a peroxo-copper complex, which proves that the formation of an intermediate (active species) retards the reaction rate. The precursor of the active species, formed during the induction period, was not the amine-copper(II) complex ion but a product of the latter with H2O2. It proved impossible to carry out the decomposition in acid or buffer solutions, in which the resin is regenerated.

The role of resin—transition metal complexes containing hydroxy amine ligand in hydrogen peroxide decomposition

Abstract The catalytic decomposition of hydrogen peroxide was studied in aqueous medium in the presence of cobalt(II)—ethanolamine complexes sorbed on Dowex-50W resin. Mono-, di- and triethanolamines were used as ligands. The reaction was first order with respect to [H2O2] in all cases. The rate constant decreased with increasing degree of resin crosslinkage owing to a salting-out effect. Also, the rate constant decreased in the following order: mono->di->triethanolamine, which is the same as the order of base strength of the three amines. The activation energy decreased with increasing degree of resin crosslinkage. The other activation parameters were calculated, and the probable reaction mechanism is proposed.

Kinetics and mechanism of the oxidative color removal from Durazol Blue 8 G with hydrogen peroxide

Abstract The kinetics of oxidation of the direct dye Durazol Blue 8G with H2O2 was studied spectrophotometrically in different media. An induction period was observed at the early stages of the reaction. The slowness of the oxidation reaction was a precursor of an autocatalytic behaviour. The absorbance A=f(t) curve has a sigmoid character with a point of inflection which is typical of autocatalytic reactions. The kinetic and activation parameters were determined at time tending to zero (t→0) and in the bulk for uncatalyzed and autocatalyzed reactions. The reaction followed zero-order kinetics with respect to [dye] and first-order kinetics with respect to [H2O2]. The reaction at t=0 followed a first-order kinetics for both [dye] and H2O2]. This means that the order as a function of the initial concentration was greater than that as function of time with respect to [dye]. This is an indication for the autocatalytic behaviour. The activation energy, E increases in the following order: phosphate buffer (pH > 8)=sodium tetraborate/NaOH buffer

Phase transformation and thermal monomerization of 9-methylanthracene photodimer

The phase change that accompanies the thermal monomerization of the 9-methylanthracene photodimer (9-MeAD) has been studied by differential scanning calorimetry (DSC), and X-ray powder diffraction, as well as fluorescence spectroscopy. 9-MeAD was chosen as a model compound since the thermal reaction product (9-methylanthracene) has a melting point that is lower than the temperature at which there is a transition from one crystalline phase to another.

Catalytic conversion of n-pentanol to 1,1-dialkyl ether by aluminium and iron exchanged montmorillonite catalyst

Abstract Heterogeneous catalytic conversion of n-pentanol to 1,1-dialkyl ether by Fe 3+ - and Al 3+ -exchanged montmorillonite catalyst was studied under different conditions. The catalyst was first heated in the presence of air or hydrogen at temperatures ranging from 80°C to 300°C and X-ray diffractometry, TGA, cation exchange capacity were performed. The final products were analysed by gas chromatography. It was found that Al 3+ -exchanged ions are more efficient as a catalyst than the corresponding Fe 3+ -exchanged ones under the same conditions.

Kinetics of heterogeneous decomposition of hydrogen peroxide

AbstractThe kinetics of the decomposition of hydrogen peroxide was studied in aqueous medium in the temperature range 25–40°C in the presence of Wofatit KPS-resin in the form of Cu(II)-ammine complex ions. The rate constant was deduced at various degrees of resin cross-linkage and different concentrations of hydrogen peroxide. The order of the decomposition reaction varied from first order to half order, i.e., the order of the reaction decreased with increasing the concentration of H2O2. The decomposition process was found to be a catalytic reaction which was controlled by the chemical reaction of H2O2 molecules with the active species inside the resin particles. The mechanism of the reaction can be summarized by the equation

Spectroscopic and stability characteristics of Ga-tetraphenyl porphyrin- and Ge- and Sn-tetra (p-methyl-phenyl) porphyrin chlorides

- {\text{d}}\left[ {{\text{H}}_{\text{2}} {\text{O}}_{\text{2}} } \right]/{\text{d}}t = k_1 {\text{ }}\sqrt {K_1 } K_2 \left[ {{\text{H}}_{\text{2}} {\text{O}}_{\text{2}} } \right]\left[ {{\text{Cu}}\left( {{\text{NH}}_{\text{3}} } \right)_4 } \right]^{2{\text{ }} + } /\left[ {{\text{H}}^{\text{ + }} } \right]