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Steinfeldt N.,Leibniz Institute for Catalysis at the University of Rostock
Langmuir | Year: 2012

The temporal evolution of Pt nanoparticle formation in ethylene glycol solution from H2PtCl6·6H2O at 90 °C for different molar ratios of NaOH to Pt (84, 6.5, and 2) in the presence or absence of poly(N-vinyl-2-pyrrolidone) (PVP) as protecting agent was followed in situ by small-angle X-ray scattering (SAXS). The SAXS profiles were analyzed regarding particle size and size distribution using the Guinier approximation and the indirect Fourier transform technique (IFT). The NaOH to Pt ratio has an influence on the integral nanoparticle formation rate as well as on the metal reduction rate and the ratio of nucleation to growth reactions. The fastest nanoparticle formation rate was observed for the NaOH/Pt ratio of 6.5. The obtained results indicate that the differences in the particle formation rate might be due to differences in the reduction rate of the formed Pt complexes. In alkaline reaction media (NaOH/Pt = 84 or 6.5), small nanoparticles with a relatively narrow size distribution were formed. Therefore, it is assumed that for these NaOH/Pt ratios the particle formation is dominated by nucleation reactions. Additionally, the in situ studies point out that nanoparticles prepared at the NaOH/Pt ratio of 84 do not grow further after attaining a certain particle size. For a NaOH to Pt ratio of 2, that means in acidic medium, particle formation should be dominated by growing processes and, therefore, larger particles are formed accompanied by a broader particle size distribution. The influence of PVP on the nanoparticle formation rate is relatively low. However, in acidic medium, the presence of PVP is necessary in order to protect the formed nanoparticles from irreversible aggregation reactions. © 2012 American Chemical Society. Source


Tlili A.,Leibniz Institute for Catalysis at the University of Rostock | Billard T.,CNRS Institute of Molecular and Supramolecular Chemistry and Biochemistry
Angewandte Chemie - International Edition | Year: 2013

Modern chemistry with an old substituent: The introduction of the SCF 3 group into organic substrates is a challenging task because of harsh or specific synthetic methods. However, recent advances in the formation of C-SCF3 bonds include the trifluoromethylthiolation with transition-metal-free systems or in the presence of palladium, nickel, or copper catalysts (see scheme). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Bruckner A.,Leibniz Institute for Catalysis at the University of Rostock
Chemical Society Reviews | Year: 2010

Electron Paramagnetic Resonance (EPR) offers widespread opportunities for monitoring catalytically relevant species that contain unpaired electrons under conditions close to those of heterogeneous catalytic gas and liquid phase reactions. In this tutorial review, after introducing basic theoretical and experimental principles of the technique, selected examples of typical applications are discussed that comprise (1) transition metal ions in paramagnetic valence states such as vanadium, (2) radical anions such as O - formed on oxide surfaces and (3) electrons in ferromagnetic particles such as nickel as well as in conduction bands of organic conductors such as polyaniline. © 2010 The Royal Society of Chemistry. Source


Bentrup U.,Leibniz Institute for Catalysis at the University of Rostock
Chemical Society Reviews | Year: 2010

Several in situ techniques are known which allow investigations of catalysts and catalytic reactions under real reaction conditions using different spectroscopic and X-ray methods. In recent years, specific set-ups have been established which combine two or more in situ methods in order to get a more detailed understanding of catalytic systems. This tutorial review will give a summary of currently available set-ups equipped with multiple techniques for in situ catalyst characterization, catalyst preparation, and reaction monitoring. Besides experimental and technical aspects of method coupling including X-ray techniques, spectroscopic methods (Raman, UV-vis, FTIR), and magnetic resonance spectroscopies (NMR, EPR), essential results will be presented to demonstrate the added value of multitechnique in situ approaches. A special section is focussed on selected examples of use which show new developments and application fields. © 2010 The Royal Society of Chemistry. Source


Grant
Agency: Cordis | Branch: H2020 | Program: MSCA-ITN-ETN | Phase: MSCA-ITN-2015-ETN | Award Amount: 3.32M | Year: 2016

Transition metal catalysts are formidable tools towards greener chemistry, allowing for low-waste, energy-efficient, and selective reactions. However, the noble metals (Ru, Os, Rh, Ir, Pd, Pt) that are currently most common in homogeneous catalysts suffer from high toxicity and environmental impact in addition to their scarcity and ensuing high cost. First-row metals (Mn, Fe, Co, Ni, Cu) are emerging as environmentally benign alternatives, but to this day rarely equal the performance of their noble counterparts. The NoNoMeCat network aims at providing excellent and structured interdisciplinary training to a generation of young researchers in the field of Non-Noble Metal homogeneous Catalysis who will push the boundaries of the field in terms of catalyst stability, selectivity, mechanistic understanding, and scalability. These challenges are addressed in three areas of high fundamental and practical significance: the oxidation of hydrocarbons, the formation of new C-X bonds (C-C, C-N) bonds through cross-coupling reactions, and clean energy production. NoNoMeCat will enrol 14 Early Stage Researchers (ESRs) who will receive structured training in experimental and theoretical aspects of non-noble metal chemistry as well as transferable skills such as research integrity, scientific communication and public outreach. Tight integration of non-academic partners will expose all ESRs to aspects of both fundamental interdisciplinary research and industrial application, paving the way for long-standing intersectorial collaborations.

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