Lacunary Keggin type polyoxotungstates in conjunction with a phase transfer catalyst: An effective catalyst system for epoxidation of alkenes with aqueous H2O2

Ingle, Rohit H.; Raj, N.K. Kala

doi:10.1016/j.molcata.2008.07.003

Cited by 23 publications

(3 citation statements)

References 20 publications

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“…Based on the FT-IR observation, we propose the same mechanism (Scheme 1) as reported by Ingle et al [45]. Kinetics A detailed study on the kinetic behavior was carried out for both catalysts.…”

Section: Reaction Mechanismsupporting

confidence: 67%

Supported dodecaphosphotungstate and undecaphosphotungstate: a study on the kinetic behavior for the oxidation of styrene

Shringarpure

Patel

2011

Reac Kinet Mech Cat

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Zirconia supported dodecaphosphotungstate and undecaphosphotungstate were successfully used as heterogeneous catalysts for the liquid-phase solventfree oxidation of styrene. A detailed kinetic study was carried out in order to study the effect of removal of one addenda atom from the parent Keggin unit. The supported catalysts were also systematically characterized by various physicochemical techniques to show that the Keggin unit remains intact even after supporting on the support. Thermal studies also indicate that the supported catalysts are stable up to 450°C. Maximum conversion with a single selective product was obtained after 30 h for the undecaphosphotungstate and after 20 h for dodecaphosphotungstate. The rate constants as well as the activation energy for the reaction were determined. From the values of activation energy derived from the Arrhenius plot, different thermodynamic parameters such as enthalpy and Gibbs free energy were also calculated. From the above studies, supported dodecaphosphotungstate was found to be more active as compared to undecaphosphotungstate.

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Section: Reaction Mechanismsupporting

confidence: 67%

Supported dodecaphosphotungstate and undecaphosphotungstate: a study on the kinetic behavior for the oxidation of styrene

Shringarpure

Patel

2011

Reac Kinet Mech Cat

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“…The initial extraction is favored by the formation of strong π-π interactions between aromatic sulfur compounds and the imidazolium rings of ILs [2]. The subsequent catalytic oxidation process was always related with the formation of peroxometal intermediates, according to previous works [52][53][54][55]. There were two possible catalytic oxidation mechanisms for the ODS process by H 2 O 2 in the presence of the transition metal mono-substituted phosphomolybdates as catalysts.…”

Section: The Possible Mechanismmentioning

confidence: 99%

Catalytic Oxidative/Extractive Desulfurization of Model Oil using Transition Metal Substituted Phosphomolybdates-Based Ionic Liquids

Zhang

et al. 2018

Catalysts

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Polyoxometalates based ionic liquids (POM-ILs) exhibit a high catalytic activity in oxidative desulfurization. In this paper, four new POM-IL hybrids based on transition metal mono-substituted Keggin-type phosphomolybdates, [Bmim] 5 [PMo 11 M(H 2 O)O 39 ] (Bmim = 1-butyl 3-methyl imidazolium; M = Co 2+ , Ni 2+ , Zn 2+ , and Mn 2+ ), have been synthesized and used as catalysts for the oxidation/extractive desulfurization of model oil, in which ILs are used as the extraction solvent and H 2 O 2 as an oxidant under very mild conditions. The factors that affected the desulfurization efficiency were studied and the optimal reaction conditions were obtained. The results showed that the [Bmim] 5 [PMo 11 Co(H 2 O)O 39 ] catalyst demonstrated the best catalytic activity, with sulfur-removal of 99.8%, 85%, and 63% for dibenzothiophene (DBT), 4,6-dimethyldibenzothiophene (4,6-DMDBT), and benzothiophene (BT), respectively, in the case of extraction combining with a oxidative desulfurization system under optimal reaction conditions (5 mL model oil (S content 500 ppm), n(catalyst) = 4 µmol, n(H 2 O 2 )/n(Substrate) = 5, T = 50 • C for 60 min with [Omim]BF 4 (1 mL) as the extractant). The catalyst can be recycled at least 8 times, and still has stability and high catalytic activity for consecutive desulfurization. Probable reaction mechanisms have been proposed for catalytic oxidative/extractive desulfurization.because it can proceed under mild reaction conditions, and oxidized products can be easily removed by extraction with organic extractants, owing to oxidized compounds being more polar than hydrocarbon molecules [20][21][22][23][24]. Although conventional organic extractants, including acetonitrile, methanol, dimethylsulfoxide (DMSO), dimethylformamide (DMF), sulfolane, and dichloromethane, reveal good extraction, their flammable and toxic properties limit their development and application in industries.Ionic liquids (ILs), as a class of green solvents, have numerous advantages over conventional organic solvents [25,26]. In 2001, Wasserscheid et al. first reported desulfurization of diesel fuel by extraction with ionic liquids [27]. The results demonstrated that ILs have the potential to play an important role in achieving clean fuel oil. Subsequently, significant literature has become available about desulfurization systems by extraction with various ILs, such as imidazolium-based ionic liquids [28][29][30][31], pyridiniuim-based ionic liquids [32], Lewis and Brösted acidic ionic liquids, and redox ionic liquids [7,33]. However, sulfur removal using only ILs as the extractant is insufficient and hardly meets stringent environmental regulations.Thus, researchers turned towards the addition of catalysts, combining peroxides with the ILs to achieve enhancement in efficiency. H 2 O 2 is often chosen as an oxidant in oxidative desulfurization, because it only produces water as a byproduct and is environmentally benign. Polyoxometalates (POMs) have received increasing attention as oxidative catalysts, due to their characterist...

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“…23–25 Moreover, these systems often employ halogenated organic solvents owing to their higher affinity towards organic catalysts and reactants for enhanced catalysis. 26,27 For instance, the application of PTCs has allowed the mild nitration of phenols using dilute HNO 3 acid instead of strong nitrating agents ( e.g. mixed acids, concentrated HNO 3 ) in traditional chemistry.…”

Section: Introductionmentioning

confidence: 99%

Nanoscale stirring at the liquid–liquid interface: the interfacial nano-vortexer actively converges immiscible biphasic reactants for enhanced phase-transfer catalysis

Ang,

Pereira,

Boong

et al. 2024

J. Mater. Chem. A

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Lacunary Keggin type polyoxotungstates in conjunction with a phase transfer catalyst: An effective catalyst system for epoxidation of alkenes with aqueous H2O2

Cited by 23 publications

References 20 publications

Supported dodecaphosphotungstate and undecaphosphotungstate: a study on the kinetic behavior for the oxidation of styrene

Supported dodecaphosphotungstate and undecaphosphotungstate: a study on the kinetic behavior for the oxidation of styrene

Catalytic Oxidative/Extractive Desulfurization of Model Oil using Transition Metal Substituted Phosphomolybdates-Based Ionic Liquids

Nanoscale stirring at the liquid–liquid interface: the interfacial nano-vortexer actively converges immiscible biphasic reactants for enhanced phase-transfer catalysis

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