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Frey K.,Free University of Colombia | Frey K.,Institute of Isotope and Surface Chemistry of Hungary | Iablokov V.,Free University of Colombia | Safran G.,Research Institute for Technical Physics and Materials Science | And 5 more authors.
Journal of Catalysis | Year: 2012

Non-stoichiometric Mn-oxides (MnO x and MnO y) were prepared by temperature-programmed oxidation (TPO) of Mn-oxalates, MnC 2O 4·3H 2O and MnC 2O 4·2H 2O. Both oxides provide high specific surface areas (525 m 2 g -1 and 385 m 2 g -1, respectively) and identical CO oxidation reaction rates of 10 -2 molecules nm -2 s -1 (0.017 μmol CO m -2 s -1) at 298 K. A "spinodal" transformation of oxalates into oxides was observed by transmission electron microscopy (TEM). The quantitative evaluation of TPO and temperature-programmed reduction with CO allowed x-values of 1.61, ⋯, 1.67 to be determined for MnO x. The Mn oxidation state in MnO x was found to be 3.4 ± 0.1 by X-ray absorption near-edge structure analysis and X-ray photoelectron spectroscopy. In accordance with the high specific surface area and mixed-type I/IV adsorption isotherms of MnO x, high resolution TEM demonstrated the occurrence of nested micro-rod features along with nanocrystalline particles in the endings of the rods. After CO oxidation MnO and Mn 3O 4 phases were able to be identified in the regions between rods. © 2011 Elsevier Inc. All rights reserved.

Birsa Celic T.,Slovenian National Institute of Chemistry | Rangus M.,Slovenian National Institute of Chemistry | Lazar K.,Institute of Isotope and Surface Chemistry of Hungary | Kaucic V.,Slovenian National Institute of Chemistry | Zabukovec Logar N.,Slovenian National Institute of Chemistry
Angewandte Chemie - International Edition | Year: 2012

Crystal engineering: The synthesis of the known compounds MIL-100(Fe) and MIL-45(Fe) is characterized by spectroscopy. The products are obtained under identical conditions by varying the solvent from pure water to a mixture of water and acetone. The starting solution, the gel, and the final reaction product were characterized by X-ray absorption spectroscopy (see picture). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Guczi L.,Institute of Isotope and Surface Chemistry of Hungary | Guczi L.,Institute of Nanochemistry and Catalysis | Boskovic G.,Institute of Nanochemistry and Catalysis | Kiss E.,University of Novi Sad
Catalysis Reviews - Science and Engineering | Year: 2010

Highly dispersed, oxide-or zeolite-supported bimetallic catalysts are widely used in the catalytic industry, such as in catalytic reforming, nitrogen industry and gas-to-liquid technology. The paper highlights the nano-sized Co-based bimetallic system in terms of correlation between structure and reactivity/selectivity promoted by the second metal. Opposite to the bulk alloys nano-sized bimetallic catalysts are extremely sensitive to the structure, morphology, valence state of the supporting oxide material in which the nano-particles are embedded. In this case, one of the less reducible components, which strongly interact with the supports, may stabilize the second, more noble metals, and thus the latter can be stabilized in highly dispersed state. Conversely, addition of noble metal to the hardly reducible component may facilitate reduction, which causes the retardation of the deactivation process of some hydrocarbon reaction. The future trend is the application of bimetallic nano-particles although careful consideration and experimentation should be taken to elucidate the structure of such type of catalyst. The various effects of Co-based bimetallic particles, such as particle size, metal/support interface, morphology and electronic effects, on the activity/selectivity in given catalytic reactions will be discussed. © Taylor & Francis Group, LLC.

Ignatovych M.,Ukrainian Academy of Sciences | Fasoli M.,University of Milan Bicocca | Kelemen A.,Institute of Isotope and Surface Chemistry of Hungary
Radiation Physics and Chemistry | Year: 2012

Spectrally resolved thermoluminescence (TL) of non-doped and Ag, Cu- and Mn-doped lithium-tetraborate (LTB) single crystals revealed that TL emission bands for differently doped samples proved to be at different wavelengths: 272, 370 and 608nm, respectively. These bands perfectly agree with the photoluminescence (PL) emission bands of Ag+, Cu+ and Mn2+ ions. It strongly points that these dopants are directly involved as recombination centers in the TL process.TL characteristics of non-doped and doped LTB single crystals and the corresponding glassy samples showed that their TL intensities and the structures of the glow curves were apparently different. © 2012 Elsevier Ltd.

Lazar K.,Institute of Isotope and Surface Chemistry of Hungary
Hyperfine Interactions | Year: 2012

Some applications of Mössbauer spectroscopy are presented with environmental implications. In particular, catalytic processes are discussed with examples for catalyst immobilisation, for removal of contaminants and for decomposition of harmful compounds. Examples are also presented for processes of recycling of end products. © 2011 Springer Science+Business Media B.V.

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