Molecular ruthenium‐based water oxidation catalyst precursors of general formula Ru(tda)(Li)2 (tda2− is 2,2′:6′,2′′‐terpyridine‐6,6′′‐dicarboxylato; ...L1=4‐(pyren‐1‐yl)‐N‐(pyridin‐4‐ylmethyl)butanamide, 1 b; L2=4‐(pyren‐1‐yl)pyridine), 1 c), have been prepared and thoroughly characterized. Both complexes contain a pyrene group allowing ready and efficiently anchoring via π interactions on multi‐walled carbon nanotubes (MWCNT). These hybrid solid state materials are exceptionally stable molecular water‐oxidation anodes capable of carrying out more than a million turnover numbers (TNs) at pH 7 with an Eapp=1.45 V vs. NHE without any sign of degradation. XAS spectroscopy analysis before, during, and after catalysis together with electrochemical techniques allow their unprecedented oxidative ruggedness to be monitored and verified.
A million TONs: Oxidatively stable molecular water oxidation anodes reaching more than a million turnover numbers with no molecular degradation are achieved by using a ruthenium‐based molecular catalyst anchored on a multi‐walled carbon nanotube.
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► The use of soluble-metal NPs as catalysts in the Fischer–Tropsch synthesis provides high levels of activity and selectivity. ► The fine tuning of the M-NPs mean diameter and size ...dispersion, the choice of the stabiliser and solvent are crucial to obtain efficient catalysts. ► Water is a suitable solvent for the application of unsupported Ru-, Co- and Fe-NPs as catalysts in the Fischer–Tropsch reaction. ► Highlights of the results obtained in FT synthesis using supported nanoparticles are also included.
In this review, the current state of the art in the synthesis of soluble-Ru, Co and Fe-nanoparticles stabilised by organic molecules is described. Polymers are widely applied for the synthesis of soluble-Ru, Co and Fe-NPs, whereas the application of surfactants, ionic liquids and small molecules is much more limited.
The recent applications of soluble-metal NPs as catalysts in the Fischer–Tropsch synthesis are described. The application of soluble-metal nanocatalysts in the Fischer–Tropsch reaction using water, ionic liquids and high boiling point organic solvents is reviewed showing that higher activities and selectivities than those obtained using conventional supported catalysts can be achieved.
A facile and straightforward methodology for the preparation of monometallic (copper and palladium) and bimetallic nanocatalysts (NiCu and PdCu) stabilized by a N‐heterocyclic carbene ligand is ...reported. Both colloidal and supported nanoparticles (NPs) on carbon nanotubes (CNTs) were prepared in a one‐pot synthesis with outstanding control on their size, morphology and composition. These catalysts were evaluated in the selective hydrogenation of alkynes and alkynols. PdCu/CNTs revealed an efficient catalytic system providing high selectivity in the hydrogenation of terminal and internal alkynes. Moreover, this catalyst was tested in the semi‐hydrogenation of acetylene in industrially relevant acetylene/ethylene‐rich model gas feeds and showed excellent stability even after 40 h of reaction.
Working alone and together: A facile and straightforward methodology for the preparation of monometallic (copper and palladium) and bimetallic nanocatalysts (NiCu and PdCu) stabilized by a N‐heterocyclic carbene ligand is reported. Both colloidal and supported nanoparticles (NPs) on carbon nanotubes (CNTs) were prepared and tested for selective hydrogenations of alkynes and alkynols.
The first phosphine-free Pd-catalysed double carbonylation of aryl iodides is reported as a general and practical method, giving excellent conversions and selectivities for a wide range of aryl ...iodides and amine nucleophiles under atmospheric CO pressure.
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A series of colloidal cobalt nanoparticles of ca. 2.6nm stabilized by several polymeric stabilizers were synthesized in water using sodium borohydride as reducing agent and ...subsequently immobilized on TiO2. Both colloidal and TiO2 supported NPs were characterized by TEM, HRTEM, XRD, XPS, TGA and ICP techniques and the catalytic performance of the supported NPs evaluated in the Fischer–Tropsch synthesis. Important differences in terms of activity were observed depending on the polymeric stabilizers used for the synthesis of the CoNPs. These differences were correlated with the catalyst reducibility, the presence of polymer stabilizer and boron and the reduction degree at the metal surface. From the tested catalysts, the NPs prepared in the presence of poly(2-ethyl-2-oxazoline) as stabilizer resulted to be the most active of the series, which was correlated with the higher reducibility of this catalyst.
Ru and Rh nanoparticles (NPs) RuI, RuII, RhI and RhII, stabilised by triphenylphosphine (PPh3) and diphenylphosphinobutane (dppb) were synthesised, characterised and applied as catalysts in the ...hydrogenation of several aromatic ketones. The effects of the nature of the metal and of the stabilising agent on the aryl versus ketone hydrogenation were studied. For Rh NPs, the coordination of arene dominates the interaction of the substrate with the NP, whereas the coordination of the ketone group was not evidenced. For Ru NPs, however, the results show that both arene and ketone coordinate to the NPs surface in a competitive manner. The properties of the stabilising ligands have a clear influence on the outcome of the reaction, and for the Rh‐catalysed reactions, products of hydrogenolysis were only formed if PPh3 was used as the stabiliser. The structure of the substrate was also a key factor for the selectivity.
Name that tune: The selectivity of the arene versus ketone reduction of aryl ketones using Ru and Rh nanoparticles stabilized by triphenylphosphine and diphenylphosphinobutane depends on the metal, the stabilizing ligand, and structural factors in the substrates. Some general clues to understand this process are provided.
A series of novel ONO ligands bearing an ionic pendant-armed (hereinafter indicated as ONONu, where Nu corresponds to an anionic nucleophile) were synthesized, characterized, and successfully ...coordinated to cobalt and manganese precursors. New air-stable cobalt (III) complexes (1–6) and manganese (II) complexes (7 and 8) were obtained and characterized. Single crystal X-ray diffraction analysis of the Co(III) compound 5 confirmed the presence of two quaternized ligands coordinated to the metal and iodide as counterion. These novel complexes were revealed to be active catalysts in the coupling reaction of carbon dioxide and propylene oxide (PO) in different degrees of success. Among these, the manganese complex 8 afforded the best results towards the formation of propylene carbonate (PC) with a productivity of 256 kg PC/(kg cat·h), achieving a TON of 4860.
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•Experiments and simulations are performed for a stirred multiphase reactor.•Three flow regimes are observed and characterized for two reactor configurations.•Mass transfer rates in ...bubbly flow are 30% larger for the unbaffled reactor.•Mass transfer rates drop 65% when the emulsion is formed.•In the most unfavorable case 90% of the final concentration is reached in 10s.
The numerical prediction of mass transfer rates of gas components within the liquid phase in a stirred two-phase flow reactor is presented. Experiments have been conducted to determine the flow regime and the number and sizes of the bubbles formed under different conditions. The dynamic field of the two-phase flow was obtained through numerical simulations. Bubbles with the experimentally measured diameter were released from the free surface and tracked numerically to compute the particle Reynolds number, which is used to determine the mass transfer rates. The unbaffled reactor provides mass transfer rates 30% larger than the baffled reactor for the bubbly flow. Mass transfer rates drop about 65% when the emulsion is formed. Therefore, above the critical rotation rate at which the emulsion forms for the unbaffled reactor, the baffled configuration provides larger mass transfer rates. The results indicate that even for the most unfavorable case mass transfer is not the limiting step, as 90% of the equilibrium concentration is reached in 10s.
Abstract
The synthesis of two series of catalysts based on ligand‐capped supported Pd nanoparticles was carried out using a simple procedure and the resulting materials were tested in the formate ...synthesis. Within these series, PPh
3
revealed the most appropriate stabilizing ligand while TiO
2
was the most efficient support for these catalysts. The hydrogenation of CO
2
was carried out under mild reaction conditions (1.8 MPa CO
2
, 1.8 MPa H
2
, 60 °C) using water as solvent and in the presence of a base, providing excellent selectivity towards formates with a TON of 1032 (TOF of 69 h
−1
, HCOOK=1.1 mol/l).
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