Oxidizing Agent

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Rajiv Kumar - One of the best experts on this subject based on the ideXlab platform.

  • highly selective epoxidation of olefinic compounds over ts 1 and ts 2 redox molecular sieves using anhydrous urea hydrogen peroxide as Oxidizing Agent
    Journal of Catalysis, 2002
    Co-Authors: S C Laha, Rajiv Kumar
    Abstract:

    Abstract Highly selective epoxidation of different olefinic compounds was carried out using urea–hydrogen peroxide adduct (UHP) as the Oxidizing Agent in the presence of TS-1 and TS-2 as redox catalysts. A considerable increase in the epoxide selectivity was observed for different unsaturated compounds, such as allylic (allyl alcohol, allyl chloride, allyl bromide, and methylallyl chloride), open-chain, and cyclic (1-hexene and cyclohexene) and aromatic (styrene and allylbenzene) olefinic compounds, when UHP and U+HP (urea and aqueous H 2 O 2 added separately for the in situ formation of UHP) were used as oxidants instead of aqueous H 2 O 2 . The controlled release of anhydrous H 2 O 2 from UHP is the main reason for enhanced epoxide selectivity. Direct spectroscopic evidences for the formation of different Ti-superoxo complexes by the solid–solid interaction between TS-1/TS-2 and urea–hydrogen peroxide adduct were obtained from the characteristic continuous absorption band in the UV–vis region (300–500 nm) and the anisotropic EPR spectra for the superoxide radical attached to Ti(IV) centers on TS-1 and TS-2.

  • Highly Selective Epoxidation of Olefinic Compounds over TS-1 and TS-2 Redox Molecular Sieves Using Anhydrous Urea–Hydrogen Peroxide as Oxidizing Agent
    Journal of Catalysis, 2002
    Co-Authors: S C Laha, Rajiv Kumar
    Abstract:

    Abstract Highly selective epoxidation of different olefinic compounds was carried out using urea–hydrogen peroxide adduct (UHP) as the Oxidizing Agent in the presence of TS-1 and TS-2 as redox catalysts. A considerable increase in the epoxide selectivity was observed for different unsaturated compounds, such as allylic (allyl alcohol, allyl chloride, allyl bromide, and methylallyl chloride), open-chain, and cyclic (1-hexene and cyclohexene) and aromatic (styrene and allylbenzene) olefinic compounds, when UHP and U+HP (urea and aqueous H 2 O 2 added separately for the in situ formation of UHP) were used as oxidants instead of aqueous H 2 O 2 . The controlled release of anhydrous H 2 O 2 from UHP is the main reason for enhanced epoxide selectivity. Direct spectroscopic evidences for the formation of different Ti-superoxo complexes by the solid–solid interaction between TS-1/TS-2 and urea–hydrogen peroxide adduct were obtained from the characteristic continuous absorption band in the UV–vis region (300–500 nm) and the anisotropic EPR spectra for the superoxide radical attached to Ti(IV) centers on TS-1 and TS-2.

  • selective epoxidation of styrene to styrene oxide over ts 1 using urea hydrogen peroxide as Oxidizing Agent
    Journal of Catalysis, 2001
    Co-Authors: S C Laha, Rajiv Kumar
    Abstract:

    Abstract The use of anhydrous urea–hydrogen peroxide adduct as an Oxidizing Agent in the epoxidation of styrene catalyzed by a titanium–silicate (TS-1) molecular sieve resulted in very high selectivity (∼85%) for styrene oxide. When aqueous hydrogen peroxide (H 2 O 2 ) was used for styrene epoxidation, the styrene oxide selectivity was very poor (5–10%) mainly due to its isomerization into phenylacetaldehyde. The formation of different types of Ti–superoxo complexes was also observed by the solid–solid interaction with anhydrous urea–hydrogen peroxide and TS-1. It was confirmed by the characteristic continuous absorption band in the UV-Vis region (300–500 nm) and also by an intense and anisotropic EPR spectrum for the superoxide radical ion stabilized on Ti (IV) centers of TS-1 samples.

  • Selective Epoxidation of Styrene to Styrene Oxide over TS-1 Using Urea–Hydrogen Peroxide as Oxidizing Agent
    Journal of Catalysis, 2001
    Co-Authors: S C Laha, Rajiv Kumar
    Abstract:

    Abstract The use of anhydrous urea–hydrogen peroxide adduct as an Oxidizing Agent in the epoxidation of styrene catalyzed by a titanium–silicate (TS-1) molecular sieve resulted in very high selectivity (∼85%) for styrene oxide. When aqueous hydrogen peroxide (H 2 O 2 ) was used for styrene epoxidation, the styrene oxide selectivity was very poor (5–10%) mainly due to its isomerization into phenylacetaldehyde. The formation of different types of Ti–superoxo complexes was also observed by the solid–solid interaction with anhydrous urea–hydrogen peroxide and TS-1. It was confirmed by the characteristic continuous absorption band in the UV-Vis region (300–500 nm) and also by an intense and anisotropic EPR spectrum for the superoxide radical ion stabilized on Ti (IV) centers of TS-1 samples.

  • epoxidation of styrene over a titanium silicate molecular sieve ts1 using dilute h2o2 as Oxidizing Agent
    Journal of Catalysis, 1995
    Co-Authors: S Kumar, S P Mirajkar, Godwin C G Pais, Pradeep Kumar, Rajiv Kumar
    Abstract:

    Abstract The epoxidation of styrene was studied using a titanium silicate molecular sieve TS-1 as catalyst and dilute (25%) H 2 O 2 as Oxidizing Agent. Mainly two types of reactions were observed: The major reaction (∼75-85 mole%) was epoxidation and its further isomerization into phenylacetaldehyde. The other reaction was oxidative cleavage into benzaldehyde (∼10-20 mole%). While generally the products were analyzed by capillary GC and GCMS, in certain cases, the products were separated and isolated by column chromatography and analyzed by 1 H and 13 C NMR spectroscopy. Polar and nonpolar solvents have marked influence on product distribution in styrene epoxidation. In methanol, a significant part of styrene epoxide undergoes alcoholysis through the addition of methanol forming 2-methoxy-2-phenyl-ethanol. The influence of reaction time, temperature, and styrene/H 2 O 2 molar ratio on the conversion and product distribution was also studied.

S C Laha - One of the best experts on this subject based on the ideXlab platform.

  • highly selective epoxidation of olefinic compounds over ts 1 and ts 2 redox molecular sieves using anhydrous urea hydrogen peroxide as Oxidizing Agent
    Journal of Catalysis, 2002
    Co-Authors: S C Laha, Rajiv Kumar
    Abstract:

    Abstract Highly selective epoxidation of different olefinic compounds was carried out using urea–hydrogen peroxide adduct (UHP) as the Oxidizing Agent in the presence of TS-1 and TS-2 as redox catalysts. A considerable increase in the epoxide selectivity was observed for different unsaturated compounds, such as allylic (allyl alcohol, allyl chloride, allyl bromide, and methylallyl chloride), open-chain, and cyclic (1-hexene and cyclohexene) and aromatic (styrene and allylbenzene) olefinic compounds, when UHP and U+HP (urea and aqueous H 2 O 2 added separately for the in situ formation of UHP) were used as oxidants instead of aqueous H 2 O 2 . The controlled release of anhydrous H 2 O 2 from UHP is the main reason for enhanced epoxide selectivity. Direct spectroscopic evidences for the formation of different Ti-superoxo complexes by the solid–solid interaction between TS-1/TS-2 and urea–hydrogen peroxide adduct were obtained from the characteristic continuous absorption band in the UV–vis region (300–500 nm) and the anisotropic EPR spectra for the superoxide radical attached to Ti(IV) centers on TS-1 and TS-2.

  • Highly Selective Epoxidation of Olefinic Compounds over TS-1 and TS-2 Redox Molecular Sieves Using Anhydrous Urea–Hydrogen Peroxide as Oxidizing Agent
    Journal of Catalysis, 2002
    Co-Authors: S C Laha, Rajiv Kumar
    Abstract:

    Abstract Highly selective epoxidation of different olefinic compounds was carried out using urea–hydrogen peroxide adduct (UHP) as the Oxidizing Agent in the presence of TS-1 and TS-2 as redox catalysts. A considerable increase in the epoxide selectivity was observed for different unsaturated compounds, such as allylic (allyl alcohol, allyl chloride, allyl bromide, and methylallyl chloride), open-chain, and cyclic (1-hexene and cyclohexene) and aromatic (styrene and allylbenzene) olefinic compounds, when UHP and U+HP (urea and aqueous H 2 O 2 added separately for the in situ formation of UHP) were used as oxidants instead of aqueous H 2 O 2 . The controlled release of anhydrous H 2 O 2 from UHP is the main reason for enhanced epoxide selectivity. Direct spectroscopic evidences for the formation of different Ti-superoxo complexes by the solid–solid interaction between TS-1/TS-2 and urea–hydrogen peroxide adduct were obtained from the characteristic continuous absorption band in the UV–vis region (300–500 nm) and the anisotropic EPR spectra for the superoxide radical attached to Ti(IV) centers on TS-1 and TS-2.

  • selective epoxidation of styrene to styrene oxide over ts 1 using urea hydrogen peroxide as Oxidizing Agent
    Journal of Catalysis, 2001
    Co-Authors: S C Laha, Rajiv Kumar
    Abstract:

    Abstract The use of anhydrous urea–hydrogen peroxide adduct as an Oxidizing Agent in the epoxidation of styrene catalyzed by a titanium–silicate (TS-1) molecular sieve resulted in very high selectivity (∼85%) for styrene oxide. When aqueous hydrogen peroxide (H 2 O 2 ) was used for styrene epoxidation, the styrene oxide selectivity was very poor (5–10%) mainly due to its isomerization into phenylacetaldehyde. The formation of different types of Ti–superoxo complexes was also observed by the solid–solid interaction with anhydrous urea–hydrogen peroxide and TS-1. It was confirmed by the characteristic continuous absorption band in the UV-Vis region (300–500 nm) and also by an intense and anisotropic EPR spectrum for the superoxide radical ion stabilized on Ti (IV) centers of TS-1 samples.

  • Selective Epoxidation of Styrene to Styrene Oxide over TS-1 Using Urea–Hydrogen Peroxide as Oxidizing Agent
    Journal of Catalysis, 2001
    Co-Authors: S C Laha, Rajiv Kumar
    Abstract:

    Abstract The use of anhydrous urea–hydrogen peroxide adduct as an Oxidizing Agent in the epoxidation of styrene catalyzed by a titanium–silicate (TS-1) molecular sieve resulted in very high selectivity (∼85%) for styrene oxide. When aqueous hydrogen peroxide (H 2 O 2 ) was used for styrene epoxidation, the styrene oxide selectivity was very poor (5–10%) mainly due to its isomerization into phenylacetaldehyde. The formation of different types of Ti–superoxo complexes was also observed by the solid–solid interaction with anhydrous urea–hydrogen peroxide and TS-1. It was confirmed by the characteristic continuous absorption band in the UV-Vis region (300–500 nm) and also by an intense and anisotropic EPR spectrum for the superoxide radical ion stabilized on Ti (IV) centers of TS-1 samples.

Katsumi Yoshino - One of the best experts on this subject based on the ideXlab platform.

  • highly conducting polypyrrole prepared from homogeneous mixtures of pyrrole Oxidizing Agent and its applications to solid tantalum capacitors
    Synthetic Metals, 1994
    Co-Authors: Masaharu Satoh, Hitoshi Ishikawa, Kosuke Amano, Etsuo Hasegawa, Katsumi Yoshino
    Abstract:

    Abstract Reaction parameters for the cationic oxidative polymerization of pyrrole are investigated for the preparation of a highly conductive material for electronic devices. The homogeneous reaction mixture is prepared by dissolving pyrrole and iron(III) dodecylbenzenesulfonate at a very low temperature of −70 °C, which gives polypyrrole with high conductivity. The conductivity increases with increasing concentrations of monomer and Oxidizing Agent. The maximum conductivity reaches 80 S/cm, which is comparable to that of electrochemically prepared film. The method is successfully used for the formation of the counter electrode of a tantalum solid capacitor. The capacitor demonstrates the proportional decrease of impedance up to the resonance frequency with capacitance above 90% of the design value.

  • Highly conducting polypyrrole prepared from homogeneous mixtures of pyrrole/Oxidizing Agent and its applications to solid tantalum capacitors
    Synthetic Metals, 1994
    Co-Authors: Masaharu Satoh, Hitoshi Ishikawa, Kosuke Amano, Etsuo Hasegawa, Katsumi Yoshino
    Abstract:

    Abstract Reaction parameters for the cationic oxidative polymerization of pyrrole are investigated for the preparation of a highly conductive material for electronic devices. The homogeneous reaction mixture is prepared by dissolving pyrrole and iron(III) dodecylbenzenesulfonate at a very low temperature of −70 °C, which gives polypyrrole with high conductivity. The conductivity increases with increasing concentrations of monomer and Oxidizing Agent. The maximum conductivity reaches 80 S/cm, which is comparable to that of electrochemically prepared film. The method is successfully used for the formation of the counter electrode of a tantalum solid capacitor. The capacitor demonstrates the proportional decrease of impedance up to the resonance frequency with capacitance above 90% of the design value.

Weiguo Cheng - One of the best experts on this subject based on the ideXlab platform.

Suojiang Zhang - One of the best experts on this subject based on the ideXlab platform.

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