The Experts below are selected from a list of 1476 Experts worldwide ranked by ideXlab platform
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, 2002Co-Authors: S C Laha, Rajiv KumarAbstract: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, 2002Co-Authors: S C Laha, Rajiv KumarAbstract: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, 2001Co-Authors: S C Laha, Rajiv KumarAbstract: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, 2001Co-Authors: S C Laha, Rajiv KumarAbstract: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.
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, 2002Co-Authors: S C Laha, Rajiv KumarAbstract: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, 2002Co-Authors: S C Laha, Rajiv KumarAbstract: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, 2001Co-Authors: S C Laha, Rajiv KumarAbstract: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, 2001Co-Authors: S C Laha, Rajiv KumarAbstract: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.
James H. Espenson - One of the best experts on this subject based on the ideXlab platform.
-
kinetic study of epoxidations by Urea Hydrogen Peroxide catalyzed by methyltrioxorhenium vii on niobia
Journal of Molecular Catalysis A-chemical, 2004Co-Authors: James H. EspensonAbstract:Relative rates were measured for the heterogeneous epoxidation of olefins with Urea–Hydrogen Peroxide (UHP) in CDCl3 catalyzed by MeReO3 on Nb2O5. The rates are more selective than those in homogeneous MTO–H2O2 solutions. The reactivity orders among the alkenes are cis>trans and electron-rich > electron-poor. A molecular structure has been proposed for the active rhenium species which allows the rate differences to be explained in terms of energy gap between the alkene occupied π(CC) and unoccupied σ∗(OO) of the peroxorhenium moiety.
-
Kinetic study of epoxidations by Urea–Hydrogen Peroxide catalyzed by methyltrioxorhenium(VII) on niobia
Journal of Molecular Catalysis A-chemical, 2003Co-Authors: James H. EspensonAbstract:Relative rates were measured for the heterogeneous epoxidation of olefins with Urea–Hydrogen Peroxide (UHP) in CDCl3 catalyzed by MeReO3 on Nb2O5. The rates are more selective than those in homogeneous MTO–H2O2 solutions. The reactivity orders among the alkenes are cis>trans and electron-rich > electron-poor. A molecular structure has been proposed for the active rhenium species which allows the rate differences to be explained in terms of energy gap between the alkene occupied π(CC) and unoccupied σ∗(OO) of the peroxorhenium moiety.
-
epoxidation reactions with Urea Hydrogen Peroxide catalyzed by methyltrioxorhenium vii on niobia
Journal of Molecular Catalysis A-chemical, 2003Co-Authors: Abdillahi Omar Bouh, James H. EspensonAbstract:Abstract Soybean oils (oleic, linoleic, and linolenic acids and their methyl esters) are epoxidized readily with Urea–Hydrogen Peroxide (UHP) when methyltrioxorhenium(VII) supported on niobia is used as the catalyst in chloroform. Simple alkenes are epoxidized by the same method. The epoxide and not a diol is produced.
-
Epoxidation reactions with Urea–Hydrogen Peroxide catalyzed by methyltrioxorhenium(VII) on niobia
Journal of Molecular Catalysis A-chemical, 2003Co-Authors: Abdillahi Omar Bouh, James H. EspensonAbstract:Abstract Soybean oils (oleic, linoleic, and linolenic acids and their methyl esters) are epoxidized readily with Urea–Hydrogen Peroxide (UHP) when methyltrioxorhenium(VII) supported on niobia is used as the catalyst in chloroform. Simple alkenes are epoxidized by the same method. The epoxide and not a diol is produced.
-
oxidation of methyl trimethylsilyl ketene acetals to alpha hydroxyesters with Urea Hydrogen Peroxide catalyzed by methyltrioxorhenium
Journal of Organic Chemistry, 2000Co-Authors: Sasa Stankovic, James H. EspensonAbstract:In the presence of catalytic amounts of MTO, methyltrioxorhenium, methyl trimethylsilyl ketene acetals are oxidized with Urea Hydrogen Peroxide to afford α-hydroxy and α-siloxy esters. On treatment with potassium fluoride, the α-hydroxy esters are obtained in high yields.
Rajender S. Varma - One of the best experts on this subject based on the ideXlab platform.
-
Ti-beta-catalysed selective oxidation of sulfides to sulfoxides using Urea–Hydrogen Peroxide adduct
Chemical Communications, 1997Co-Authors: T. Indrasena Reddy, Rajender S. VarmaAbstract:Ti-Beta zeolite catalyses the selective oxidation of organic sulfides to sulfoxides with Urea–Hydrogen Peroxide adduct (UHP) as oxidant.
-
ti beta catalysed selective oxidation of sulfides to sulfoxides using Urea Hydrogen Peroxide adduct
Chemical Communications, 1997Co-Authors: Indrasena T Reddy, Rajender S. VarmaAbstract:Ti-Beta zeolite catalyses the selective oxidation of organic sulfides to sulfoxides with Urea–Hydrogen Peroxide adduct (UHP) as oxidant.
Hamid Golchoubian - One of the best experts on this subject based on the ideXlab platform.
-
Mild and highly efficient transformation of thiols to symmetrical disulfides using Urea–Hydrogen Peroxide catalyzed by a Mn(III)–salen complex
Catalysis Letters, 2006Co-Authors: Farideh Hosseinpoor, Hamid GolchoubianAbstract:The oxidative coupling of aromatic thiols into the corresponding disulfides with Urea–Hydrogen Peroxide using a Mn(III)–salen complex as catalyst under mild conditions is described. This system provides an efficient, convenient and practical method for the syntheses of symmetrical disulfides.
-
mild and highly efficient transformation of thiols to symmetrical disulfides using Urea Hydrogen Peroxide catalyzed by a mn iii salen complex
Catalysis Letters, 2006Co-Authors: Farideh Hosseinpoor, Hamid GolchoubianAbstract:The oxidative coupling of aromatic thiols into the corresponding disulfides with Urea-Hydrogen Peroxide using a Mn(III)-salen complex as catalyst under mild conditions is described. This system provides an efficient, convenient and practical method for the syntheses of symmetrical disulfides.
