The kinetics of the oxidative degradation of the indigo carmine (IC) dye (disodium salt of 3,3-dioxobi-indolin-2,2-ylidine-5,5-disulfonate) with hydrogen peroxide catalyzed with the supported metal complexes have been investigated. The complexes used are [Cu(amm)4]2+, [Co(amm)6]2+, [Ni(amm)6]2+, [Cu(en)2]2+, and [Cu(ma)4]2+ (amm=ammonia, en=ethylenediamine, and ma=methylamine). Silica, alumina, silica-alumina (25% Al2O3), and cation-exchange resins (Dowex-50W, 2 and 8% DVB) are used as supports. The reaction is first order with respect to [IC] while the order with respect to [H2O2] was dependent on the initial concentration and the type of the catalyst used. At lower [H2O2]0 the order was first, which then decreases with increasing [H2O2]0, finally reaching zero. This aspect is consistent with the formation of a colored peroxo-complex on the catalysts surface. The reactivity of catalysts is dependent on the redox potential of the metal ions, the amount of complex loaded per gram of dry catalyst, the type of ligand, and the support. Moreover, the reaction rate was strongly dependent on the pH of the medium, the cationic and anionic surfactants, and the irradiation with UV-light. The reaction is enthalpy controlled as confirmed from the isokinetic relationship. A reaction mechanism was proposed with the formation of free radicals as reactive intermediates.

Kinetics and mechanism of the heterogeneous catalyzed oxidative degradation of indigo carmine

Catalytic oxidation of styrene was investigated for polymer anchored Cu(II) and Mn(II) complexes prepared by Schiff base tridentate ligand. The effect of different oxidants, tert-butyl hydroperoxide (TBHP) under atmospheric pressure and molecular oxygen (O2) at high pressure in a batch reactor, were studied for maximum conversion of styrene and selectivity of styrene oxide product. The effect of various reaction parameters such as temperature, styrene to TBHP mole ratio, and catalyst amount were studied using TBHP as oxidant. The maximum conversion of styrene (87.3%) was obtained using Cu(II) complex, with maximum selectivity to styrene oxide (76.2%) at styrene to TBHP mole ratio of 1:3, 70 °C, and 25 mg catalyst. The O2 oxidant showed maximum conversion of 45.5% at 80 °C and 0.5 MPa pressure, with a styrene oxide selectivity of 22.4%. The catalytic activity was improved to 70.0% by addition of TBHP as initiator during the use of O2 oxidant. The Cu(II) catalyst showed better catalytic activity in comparis...

Polymer Anchored Catalysts for Oxidation of Styrene Using TBHP and Molecular Oxygen

The paper deals with oxidation of the biomass-derived model molecule 5-(hydroxymethyl)furfural (HMF) catalyzed by the trimetallic mixed oxide RuCo(OH)2CeO2. The catalyst RuCo(OH)2CeO2 was prepared through alkali hydrolysis of RuCl3, Co(NO3)2, and Ce(NO3)2 and characterized by X-ray diffraction and transmission electron microscopy techniques. RuCo(OH)2CeO2 showed high catalytic activity for aerobic oxidation of HMF under mild conditions (in the case of atmospheric oxygen pressure). Various reaction parameters such as the reaction temperature, catalyst amount, solvent, and oxidant were explored. Results demonstrated that the oxidant and solvent showed a remarkable effect on the aerobic oxidation of HMF to 2,5-diformylfuran (DFF). Under optimal conditions, DFF was obtained in a high yield of 82.6% with HMF conversion of 96.5% after 12 h at 120 °C. More importantly, the catalyst could be reused several times without significant loss of its catalytic activity.

Aerobic Oxidation of Biomass-Derived 5-(Hydroxymethyl)furfural into 2,5-Diformylfuran Catalyzed by the Trimetallic Mixed Oxide (Co–Ce–Ru)

Polymer/carbon composite material of poly(4-vinylpyridine)-functionalized carbon-nanotube (PVP/CNT) was prepared by in situ polymerization of 4-vinylpyridine monomer in the presence of CNT suspension. Raman spectra analysis confirmed the almost unchanged graphitized surfaces of CNT moiety in the PVP/CNT after the covalent functionalization of pristine CNT with PVP. Catalyst made of ruthenium complex immobilized on PVP/CNT (Ru-PVP/CNT) was fully characterized by ICP-OES, TG-DTA, FT-IR, Raman, XRD, UV-vis, BET, TEM, XPS and H2-TPR. Moreover, Ru-PVP/CNT shows excellent catalytic performance towards the selective oxidation of biomass-based 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF) with molecular oxygen as oxidant. The reaction parameters such as the reaction temperature, reaction time, solvent, catalyst amount, oxidant, and oxygen pressure were systematically investigated for this important biomass-related transformation. Under the optimal condition, a DFF yield of 94% with a full HMF conversion were obtained by using Ru-PVP/CNT in N,N-dimethylformamide (DMF) under 2.0 MPa O2 at 120 °C.

Ruthenium complex immobilized on poly(4-vinylpyridine)-functionalized carbon-nanotube for selective aerobic oxidation of 5-hydroxymethylfurfural to 2,5-diformylfuran

Rapid decomplexation of Ni-EDTA by microwave-assisted Fenton reaction

The synthesis and use of nitrogen-containing copolymers for anchoring Ru(II) and Rh(I) species is described. The supported species are effective as catalysts for the decomposition of H 2 O 2 in aqueous medium at neutral pH. The polymers as well as the supported catalysts have been characterised by physical and chemical methods. The effects of [H 2 O 2 ], catalyst loading and pH of the medium on the rate of decomposition have been studied. Suitable mechanisms have been proposed to account for the kinetics. Recycling efficiencies of the catalysts are found to be good.

V. Mahadevan

Papers

The decomposition of H2O2 catalyzed by polymer supported transition metal complexes