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CLICK IN FLOW: IMMOBILIZED Cu NANOPARTICLES FOR HUISGEN AZIDE-ALKYNE CYCLOADDITION
No full textHere we report the use of Cu nanoparticles obtained by metal vapour synthesis (MVS) supported on
commercial 3-aminopropyl functionalized silica (APSiO2) as a novel catalyst for CuAAC reactions under
continuous-flow conditions
Structural characterization of bimetallic Pd-Cu vapor derived catalysts
Full text linkPd-Cu bimetallic Solvated Metal Atoms (SMA) were synthesized by metal vapor synthesis technique and supported on PVPy resin. Since the catalytic activity, of the Pd-Cu system turned out to be quite high also compared to the corresponding monometallic system, a structural characterization, using electron microscopy techniques and X-ray Absorption Fine Structure spectroscopy, was performed. HRTEM analysis showed the presence of Pd particles distributed in a narrow range with a mean diameter of about 2.5 nm while the XAFS analysis, confirmed the presence of the Pd nanoparticles but revealed also some alloying with Cu atoms
Aminopropyl-silica supported Cu nanoparticles: an efficient catalyst for continuous-flow Huisgen azide-alkyne cycloaddtion (CuAAC)
No full textCu(I) catalyzed, Huisgen azide/alkyne 1,3-dipolar cycloaddition (CuAAC) is
recognized as the tool of choice for ligating organic molecules in a numerous fields. Out
of several catalytic systems used for CuAAC reaction, the choice of supported Cu catalysts
captured the attention of many workers to minimize the copper content in the final
products. Nonetheless almost all the studies do not provide any straightforward method
to reduce the Cu contamination in final product. The use of appropriate support and
continuous-flow conditions could contribute to solve this problem.
Here we report the use of novel Cu nanoparticles obtained by metal vapour
synthesis (MVS) supported on commercial aminopropyl-fuctionalized silica (APSiO2) as
a catalyst for CuAAC reaction in continuous-flow conditions
Ti(IV) catalytic centers grafted on different siliceous materials: Spectroscopic and catalytic study
No full textPALLADIUM NANOPARTICLES ON POLYVINYLPYRIDINE SUPPORTS: APPLICATIONS IN CONTINUOUS-FLOW MIZOROKI-HECK REACTIONS
No full textMetal vapor synthesis (MVS) technique provides a valuable synthetic route to obtain supported Pd nanoparticles featuring strictly controlled dimension (< 5 nm). These systems proved highly efficient catalysts in Mizoroki-Heck alkenylations of aryl halides (I, Br) with acrylates, to give the corresponding trans-cinnammates in high yields under batch reaction conditions.
Here we wish to report our recent results in continuous-flow Mizoroki-Heck alkenylations using MVS-derived Pd nanoparticles deposited on pyridine-based organic supports, both in the form of powder (PVPy) and as mesoporous organic monolith
Aminopropyl-silica-supported Cu nanoparticles: An efficient catalyst for continuous-flow Huisgen azide-alkyne cycloaddition (CuAAC)
Full text linkCu nanoparticles prepared by metal vapor synthesis (MVS) were immobilized on 3-aminopropyl-functionalized silica at room temperature. HRTEM analysis of the catalyst showed that the copper nanoparticles are present with mean diameters limited in the range 1.0-4.5 nm. TPR analysis was performed in order to study the oxidation state of the supported copper nanoparticles. The supported catalyst was used both in batch and in a packed-bed reactor for continuous-flow CuAAC reaction. The activation of the copper catalyst by reduction using phenyl hydrazine in continuous-flow conditions was demonstrated. Along with the high catalytic activity (productivity up to 1689 mol/mol), the catalyst can be used several times with negligible Cu leaching in the product (<9 ppm), less than allowed Cu contaminant in pharmaceuticals. The applicability of packed-bed flow reactor was showed by sequentially converting different substrates in their corresponding products using same column
Ultrafine palladium nanoparticles immobilized into poly(4-vinylpyridine)-based porous monolith for continuous-flow Mizoroki-Heck reaction
Full text linkUltrafine Pd nanoparticles (dm = 2.3 nm), obtained by metal vapor synthesis technique, were immobilized into a poly(4-vinylpyridine)-based porous monolith by means of a new synthetic approach. The synthesis involves stabilization of Pd nanoparticles with 4-vinylpyridine ligand and their subsequent immobilization into the monolith by radical co-polymerization of the resulting metal-embedding monomer with ethylene glycol dimethacrylate in presence of porogenic agents (i.e. DMF and PEG-400) inside stainless-steel columns (HPLC type). The hybrid monolithic reactors containing highly dispersed Pd nanoparticles were effectively used as catalyst for Mizoroki-Heck cross-coupling reactions carried out under continuous-flow conditions. The devices showed long life-time (>65 h) and very low Pd leaching (<2 ppm)
Solvated Metal Atoms in the Preparation of Supported Gold Catalysts
No full textSeveral reviews appeared in the last years to emphasize the unique properties showed by gold metal, when particle size falls in nanometers range. Au nanoparticles (NPs) have found uses in ceramics, medicine, and other areas. Among them the most exciting and growing field of application is undoubtedly catalysis. Historically, gold was regarded to be catalytically inert, since the discoveries made by Haruta and Hutchings. in the late 1980s: surprisingly, they demonstrated simultaneously and independently that supported gold nanoparticles are the best catalyst for low-temperature CO oxidation and ethyne chlorination to vinylchloride. In recent years, it has been shown that gold becomes active for many novel reactions of synthetic interest when stabilized in the form of nanoparticles deposited on several organic and inorganic supports. Supported Au NPs have found numerous applications as unique catalysts in aerobic oxidative processes, reduction of organic compounds, C-C coupling reactions, etc. Moreover, the ability of gold to coordinate with triple bonds has no parallel with other transition metals. Upon coordination and formation of the corresponding adduct, the alkyne becomes activated and more reactive towards nucleophiles such as alcohols, amines and hydrosilanes.
It was clearly evidenced that particle size play a crucial role in determining catalytic activity of supported gold particles in CO oxidation, as well as in others reactions. On the other hands, it has been also demonstrated that the superficial oxidation state of the metal, the nature of the support, the Au-support interface and the particle morphology may strongly affect catalytic performance of AuNPs. All these findings have increased the efforts made by scientist to investigate how the different preparation methods can affects the above mentioned factors.
In this chapter we intend to provide a synapsis of the synthesis of supported gold catalysts by the metal vapor synthesis (MVS) approach. In particular, the contribution includes the work undertaken till date in our and other research groups pointing out the key factors to control the size of Au nanoparticles by this synthetic method
Characterization of a Poly-4-Vinylpyridine-Supported CuPd Bimetallic Catalyst for Sonogashira Coupling Reactions
No full textCuPd bimetallic solvated metal atoms (SMA) synthesized by metal vapor synthesis (MVS) technique and supported on poly-4-vinylpyridine (PVPy) resin, showed significantly higher catalytic activity in Sonogashira-type carbonâcarbon coupling reactions than the corresponding monometallic Cu and Pd systems as well as their physical mixture. The analysis of the bimetallic catalyst combining transmission electron microscopy techniques and X-ray absorption fine structure (XAFS) spectroscopy revealed the presence of small Pd nanoparticles (dm=2.5 nm) while the analysis of the X-ray absorption data, at the Cu K-edge suggests the formation of thin and incomplete Cu oxide layers around the Pd-rich cores
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