Macrocellular Pd@ionic liquid@organo-Si(HIPE) heterogeneous catalysts and their use for Heck coupling reactions

International audienceSupported ionic liquid phases (SILPs) within macrocellular silica-based foams are prepared by a simple impregnation in organic solvents. Thin ionic liquid layers with thicknesses of 6 to 12 nm were obtained. The SILs mobility has been evidenced through NMR solid state spectroscopy. Subsequently, palladium salts are efficiently trapped within the SILPs, while an in situ palladium hydrogenation allowed an efficient reduction and formation of 10 nm diameter palladium metal nanoparticles. These hybrid foams are used as heterogeneous macrocellular catalysts for the Heck coupling reaction of iodobenzene and cyclohexyl acrylate, where palladium leaching appears to be very low. Despite recyclability minimized through the entrapment of detrimental ammonium salts within the macroporous network during the reaction, competitive TONs and TOFs were reached, while separation of the products can be reached at ease, due to the fact that both palladium species and by-products are trapped within the monolithic foams

Aerobic Oxidation of Alcohols in Carbon Dioxide with Silica-Supported Ionic Liquids Doped with Perruthenate

The replacement of toxic CrVI for O2 and of chlorinated solvents for supercritical carbon dioxide (or ionic liquids) in the oxidation of alcohols remains hindered by the low selectivity and activity of the current heterogeneous catalysts. Using an integrated approach that combines sol–gel entrapped perruthenate as aerobic catalyst, an encapsulated ionic liquid as solubility promoter, and scCO2 as the reaction solvent, we have developed a system capable of rapidly converting different alcohols into carbonyl compounds with complete selectivity, including substrates which are otherwise difficult to oxidise. The methodology is generally applicable and may easily be extended to other waste-free, catalytic syntheses of fine chemicals

Applications of ionosilicas in heterogeneous catalysis: Opportunities for the elaboration of new functional catalytic phases

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Synthesis of N-Guanidinium-Chitosan/Silica Hybrid Composites: Efficient Adsorbents for Anionic Pollutants

International audienceA new chitosan derivative, N-guanidinium chitosan acetate, has been synthesized by direct guanylation of chitosan by cyanamide in presence of scandium(III) triflate under mild acidic condition. Starting from this material, N-guanidinium chitosan/silica microhybrids were prepared via a sol gel method using 3-glycidoxypropyl trimethoxysilane as silica precursor. Both N-guanidinium chitosan and the N-guanidinium chitosan/silica hybrid were characterized by a range of analytical techniques such as 29Si/13C solid state NMR, FT-IR, scanning electron microscopy, thermogravimetry and elemental analysis. The characterization of the chitosan/silica hybrid indicated that this material is a highly hydrophilic nanocomposite material containing an organic core and a highly condensed silica shell. The N-guanidinium chitosan/silica microhybrids display excellent adsorption properties for anionic dyes such as methyl orange (MO) with very high capacities up to 917 mg/g. The fixation of MO as anionic dye was investigated in detail as a function of contact time, pH and the MO concentration. The adsorption kinetics of MO on N-guanidinium chitosan/silica microhybrids was more accurately described by pseudo second-order model. Langmuir isotherm model exhibited a better fit with adsorption data than Freundlich isotherm model. This work opens new possibilities for using N-guanidinium chitosan as a reusable adsorbent for water purification

Silices fonctionnalisées contenant des espèces ioniques pour la catalyse hétérogène

La catalyse hétérogène est en plein développement pour des raisons économiques, de santé et de protection environnementale. Les travaux de cette thèse s'intéressent à la préparation des silices fonctionnalisées par des sous-structures ioniques pour leur application en catalyse hétérogène. D'abord, des matériaux mésoporeux fonctionnalisés par des entités di-aryl imidazoliums ont été préparés par des réactions de post-greffage. En plus, films de type PMO contenant des entités di-aryl imidazoliums ont été synthétisés en présence d'un surfactant anionique. Ensuite, complexes carbéniques N-hétérocycliques du cuivre et du palladium supportés ont été préparés et appliqués en tant que catalyseurs organométalliques dans des réactions A3 (Cu-NHC) et de couplage de Suzuki (Pd-NHC). Les silices fonctionnalisées avec des entités imidazoliums ont également été utilisées en tant qu'organocatalyseurs des réactions de Henry et dans de cycloaddition du dioxyde de carbone aux époxydes. Des matériaux de type PMO' contenant des entités amines/ammoniums ainsi que des sous-structures zwitterioniques ont été utilisés en réactions organocatalysées de Henry et Biginelli.Heterogenous catalysis is an area in continuous development due to economical, health and environmental issues. This thesis deals with the preparation of i-silica materials for the posterior application in heterogeneous catalysis. First, di-aryl imidazolium containing silica materials were synthesized by post-grafting reactions on mesoporous SBA-15. Moreover, di-alkyl imidazolium containing PMO films were prepared in presence of an anionic surfactant. Then, supported copper and palladium N-heterocyclic carbenes were synthesized from di-aryl imidazolium silica and applied to A3 reactions (Cu-NHC) and Suzuki cross-coupling reactions (Pd-NHC). Imidazolium functionalized silicas were also utilized as heterogeneous organocatalysts in Henry reactions and in reactions of cycloaddition of carbon dioxide to epoxides. Finally, PMO type materials containing amine/ammonium and zwitterionic substructures were applied to Henry and Biginelli organocatalysed reactions, respectively.MONTPELLIER-Ecole Nat.Chimie (341722204) / SudocSudocFranceF

New N -guanidinium chitosan/silica ionic microhybrids as efficient adsorbent for dye removal from waste water

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Recent Trends in Elaboration, Processing, and Derivatization of Cellulosic Materials Using Ionic Liquids

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Adsorbenzien: Organisch-anorganische Hybride

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