Publications (6)2.94 Total impact
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Article: Direct catalytic oxidation of cyclohexene to 1, 2-cyclohexanediol by aqueous hydrogen peroxide under solvent-free condition
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ABSTRACT: Cyclohexene can be oxidized directly to 1, 2-cyclohexanediol with aqueous hydrogen peroxide under solvent-free condition using a heteropolyphosphatotungstate catalyst. And an isolated yield of 54% was obtained in this catalytic system.Research on Chemical Intermediates 04/2012; 35(5):563-571. · 0.70 Impact Factor -
Article: Secondary alcohols oxidation with hydrogen peroxide catalyzed by [ nC 16H 33N(CH 3) 3] 3PW 12O 40: Transform-and-retransform process between catalytic precursor and catalytic activity species
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ABSTRACT: [n-C16H33N(CH3)3]3PW12O40 (1a) catalyzed the oxidation of secondary alcohols with 27.5% aqueous hydrogen peroxide under solvent-free conditions. The isolated yields of all ketones were higher than 92%. The turnover number of the catalyst 1a was above 368, and the highest TON and TOF were up to 3840 and 320h−1. In this catalytic system, the catalytic active species was {PO4[WO(O2)2]4}3−, which was formed from 1a in the reaction. It was discovered that {PO4[WO(O2)2]4}3− (PW4) and [PW12O40]3− (PW12) kept an equilibrium during the alcohol oxidation by simultaneous monitoring the distribution of species in organic and aqueous phases. The analysis of the W content in the aqueous phase by ICP and the detection of the species transformation in the organic phase by 31P NMR revealed that the most of the PW4 species were transformed to the PW12 species again after the reaction. PW12 and PW4 were in the transform-and-retransform process.Journal of Molecular Catalysis A-chemical - J MOL CATAL A-CHEM. 01/2008; 289(1):22-27. -
Article: Solvent-free oxidation of alcohols catalyzed by an efficient and reusable heteropolyphosphatotungstate
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ABSTRACT: With aqueous hydrogen peroxide as oxidant, secondary alcohols could be efficiently oxidized to ketones in the presence of hexadecyl trimethyl ammonium heteropolyphosphatotungstate ((n-C16H33N(CH3)3)3[PW4O16]) under solvent-free conditions. The oxidation of alcohol over 0.5mol% (based on molar amount of hydrogen peroxide) catalyst occurred at 90°C to give the corresponding ketones with above 92% yield and 97% selectivity. The catalyst could be reused without loss of selectivity.Catalysis Communications - CATAL COMMUN. 01/2007; 8(3):531-534. -
Article: Epoxidation of Allyl Chloride to Epichlorohydrin by a Reversible Supported Catalyst with H2O2 under Solvent-Free Conditions
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ABSTRACT: Allyl chloride was epoxidized to epichlorohydrin with H2O2 under solvent-free conditions in 94% selectivity using a new reversible supported catalyst, heteropolyphosphatotungstate/silanized silica gel. By the action of H2O2 the heteropolyphosphatotungstate dissolves from the carrier surface and forms an active homogeneous reagent. When all H2O2 is consumed, the reduced catalyst redeposits on the support carrier. The supported catalyst retains the character of a homogeneous catalyst during reaction but exhibits heterogeneous properties upon work-up. The solid-supported catalyst is easily isolated and can be reused. The reaction system for synthesis of epichlorohydrin therefore avoids the serious pollution issues known from the commercialized chlorohydrin methods. Some other olefins can also be epoxidized by this catalytic system under neat conditions.07/2006; -
Article: Reaction-Controlled Phase Transfer Catalysis for Styrene Epoxidation to Styrene Oxide with Aqueous Hydrogen Peroxide
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ABSTRACT: The epoxidation of styrene catalyzed by a reaction-controlled phase transfer catalyst [(C18H37 (30%)+C16H33(70%))N(CH3)3]3[PW4O16] with H2O2 in a biphasic medium was investigated. Under certain conditions, the selectivity for styrene oxide was 95%, the conversion of styrene based on H2O2 was 85%, and the reaction time was less than 1 h. During the reaction, this catalyst powder formed soluble active species by the action of H2O2, was recovered as a precipitate, and was reused after H2O2 was used up. After two times recycling, the catalyst kept almost the same activity.03/2005; -
Article: On the Nature of Reaction-Controlled Phase Transfer Catalysts for Epoxidation of Olefin: A 31P NMR Investigation
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ABSTRACT: [-C5H5NC16H33]3[PW4O16] was reported to be an excellent epoxidation catalyst which exhibited a unique reaction-controlled phase transfer behavior. In the paper, the composition and structural changes of the reaction-controlled phase transfer catalyst during and after reaction have been investigated by 31P NMR spectroscopy. The 31P MAS NMR confirmed that the original catalyst was a mixture of heteropoly tungstophosphates. When the catalyst reacted with hydrogen peroxide, the species PO4[WO(O2)2]4 3–, [(PO4)WO(O2)2 2WO(O2)2(H2O)]3– and [(PO3(OH))WO(O2)2 2]2– were detected by in situ 31P NMR. It was also found that the P/W ratios and quaternary ammonium cations had great influence on the composition of heteropoly tungstophosphates. Although the catalyst with [(C18H37)2N(CH3)2]+ was not a reaction-controlled phase transfer catalyst, it could be precipitated from the reaction solution when acetone was subsequently added to the solution. The 31P MAS NMR spectra of the recovered catalysts revealed that they had more low P/W ratio heteropoly tungstophosphates than fresh catalysts.Catalysis Letters 01/2004; 93(1):41-46. · 2.24 Impact Factor -
Article: Epoxidation of Propylene with Aqueous Hydrogen Peroxide on a Reaction-Controlled Phase-Transfer Catalyst
11/2003;
