Search results for "HETEROGENEOUS CATALYSIS"
showing 10 items of 233 documents
Activity of a Heterogeneous Catalyst in Deep Eutectic Solvents: The Case of Carbohydrate Conversion into 5-Hydroxymethylfurfural
2019
Obtaining industrially relevant products from renewable resources and developing processes under the light of sustainable chemistry is a prominent endeavor of present-day chemical research. In this context, herein we investigated the dehydration of fructose and sucrose in deep eutectic solvents promoted by the ion-exchange resin Amberlyst 15 as heterogeneous catalyst. We optimized the reaction conditions in terms of temperature, catalyst loading, and initial amount of substrate. Then, we looked at the effect of structural variations in the solvent components on the reaction outcome. Under the best experimental conditions, we obtained very good yields of 78% at 60 °C and 69% at 80 °C for fru…
ChemInform Abstract: Recyclable Heterogeneous Palladium Catalysts in Pure Water: Sustainable Developments in Suzuki, Heck, Sonogashira and Tsuji-Tros…
2010
This review summarizes the progress made essentially these last ten years on heterogeneous palladium catalysis in pure water. The work covers four important palladium-catalyzed transformations for carbon-carbon bond formation: Suzuki, Heck, Sonogashira and Tsuji-Trost reactions. The discussion focuses on the efficiency and reusability of the heterogeneous catalysts as well as on the experimental conditions from a sustainable chemistry point of view. The review is introduced by a discussion on mechanistic aspects inherent to heterogeneous catalysis.
Cluster Preface: Heterogeneous Catalysis
2016
International audience; Jean-Cyrille Hierso is full professor of Chemistry since 2009, heading the group of ‘Organometallic Chemistry and Catalysis’ at the Institute of Molecular Chemistry at the University of Bourgogne Franche-Comté (UBFC). He has interest in the fields of organometallic chemistry, ligand design, homo- and heterogeneous catalysis, chemical physics, and material sciences. In 2011 he was awarded the National Prize for Coordination Chemistry from the French Chemical Society (SCF), and at the end of 2012 he was elected a junior Member of the French Professors Academy ‘Institut Universitaire de France’ (IUF).Yasuhiro Uozumi is a full professor at the Institute for Molecular Sci…
Carbon dioxide conversion to dimethyl carbonate: The effect of silica as support for SnO2 and ZrO2 catalysts
2011
International audience; Abundant in nature, CO2 poses few health hazards and consequently is a promising alternative to phosgene feedstock according with the principles of Green Chemistry and Engineering. The synthesis organic carbonates from CO2 instead of phosgene is highly challenging as CO2 is much less reactive. As part of our ongoing research on the investigation of catalysts for dimethyl carbonate (DMC) synthesis from methanol and CO2, we herein report results aimed at comparing the catalytic behavior of new SnO2-based catalysts with that of ZrO2. Silica-supported SnO2 and ZrO2 exhibit turnover numbers which are an order of magnitude higher than those of the unsupported oxides. Tin-b…
An E-Factor Minimized Protocol for a Sustainable and Efficient Heck Reaction in Flow
2014
A highly sustainable and waste-minimized protocol for Heck coupling has been defined. Optimal conditions have been defined by exploiting a heterogeneous catalyst based on supported ionic liquid-like phases featuring high Pd loading (10 wt %) and by optimizing its efficiency in a recoverable green reaction medium (acetonitrile/water azeotrope). Pure products 4a–l and 6a–h have been isolated chromatography-free in high yields (74–99%) and with extremely low environmental factor (E-factor) values (2.3–5.0). With the application of flow technology, the selected heterogeneous base and Pd catalyst have been fully recovered and reused, and minimum palladium leaching allowed for isolation of the fi…
Recyclable heterogeneous palladium catalysts in pure water: sustainable developments in Suzuki, Heck, Sonogashira and Tsuji-Trost reactions
2010
This review summarizes the progress made essentially these last ten years on heterogeneous palladium catalysis in pure water. The work covers four important palladium-catalyzed transformations for carbon-carbon bond formation: Suzuki, Heck, Sonogashira and Tsuji-Trost reactions. The discussion focuses on the efficiency and reusability of the heterogeneous catalysts as well as on the experimental conditions from a sustainable chemistry point of view. The review is introduced by a discussion on mechanistic aspects inherent to heterogeneous catalysis.
Structural insight on organosilica electrodes for waste-free alcohol oxidations
2007
Organic modification of sol-gel catalytic glassy electrodes made of a thin layer of organosilica doped with nitroxyl radical TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) crucially enhances stability in the waste-free oxidation of alcohols to carbonyls in water. Structural comparison between analogous films made of organosilica and unmodified SiO2 shows that the origin of the pronounced stable activity of the ORMOSIL film lies in high hydrophobic and also in the pronounced low degree of hydrophilicity.
Kinetic Aspects of Heterogeneous Catalytic Versus Photocatalytic Reactions
2019
Abstract Kinetics aspects of heterogeneous catalysis and photocatalysis are reported together with the most used models developed for both fields. The chapter describes the main mechanisms involved in the different processes and the parameters used to determine their performances. A comparison of the behaviors and kinetics features of heterogeneous catalysis and photocatalysis is presented.
Cross-Linked Polyamine from Imidazolium-Based Materials: A Simple Route to Useful Catalytic Materials
2018
Cross-linked polyamine-based materials were easily prepared by reduction of the corresponding cross-linked imidazolium-based materials with sodium borohydride in hot ethanol. Overall, the synthetic procedure is based on the polymerization of a suitable bis-vinylimidazolium salt with or without a suitable support, such as silica or silica-coated magnetic nanoparticles (γ-Fe2O3@SiO2), followed by reduction. This simple approach allows the synthesis of materials based on a network of secondary and tertiary amines. Materials were characterized by13C cross-polarization magic angle spinning NMR (13C CPMAS NMR), proton spin-lattice relaxation times in the rotating frame (T1ÏH) and thermogravimet…
Thiazolium-‐based catalysts for the etherification of benzylic alcohols under solvent-free conditions
2015
In this work, thiazolium and imidazolium hybrid materials (SBA-15-Thia and SBA-15-Imi) were prepared by grafting the bis-vinylthiazolium or imidazolium salts onto thiol functionalized SBA-15 mesostructured silica. The catalytic activity was tested for the etherification of 1-phenylethanol, in heterogeneous conditions. The reactions were performed under different gas phases and reaction times. The SBA-15-Thia displayed an excellent catalytic performance, also with others benzyl alcohols. This material was successfully used in seven consecutive runs. Further studies were carried out in homogenous conditions. The results obtained allow proving that oxygen play an active role in the reaction pr…