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Joo F.,Debrecen University | Joo F.,Mta Of Homogeneous Catalysis And Reaction Mechanisms Research Group
ChemCatChem | Year: 2014

G'day, formate! The recent breakthrough discovery by Beller etal. in the production of formate salts by combined dehydrogenation of methanol and hydrogenation of bicarbonates is discussed. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Balogh A.,Debrecen University | Lente G.,Debrecen University | Kalmar J.,Mta Of Homogeneous Catalysis And Reaction Mechanisms Research Group | Fabian I.,Debrecen University
International Journal of Chemical Kinetics | Year: 2015

A detailed kinetic analysis of two schemes, one involving coupled consecutive processes and another featuring the simultaneous association reaction and decay of a component, is presented here using Taylor series expansion. It is shown that both of these schemes are easily confused with the reversible second-order reaction in a routine kinetic study. The kinetic traces predicted by both schemes are sufficiently close to pseudo-first-order curves so that it is practically impossible to identify the deviations based on data with the usual experimental errors, which was also demonstrated by fitting simulated theoretical curves to exponential functions. The dependence of the pseudo-first-order rate constants on the concentration of the excess reagent features the same trend as in the case of a reversible reaction: A straight line with an intercept is observed. This analysis emphasizes that the reversible nature of reactions should be demonstrated by direct equilibrium studies when elements of reversibility are implied by kinetic results. © 2015 Wiley Periodicals, Inc.

Kalmar J.,Mta Of Homogeneous Catalysis And Reaction Mechanisms Research Group | Lente G.,Debrecen University | Fabian I.,Debrecen University
Dyes and Pigments | Year: 2016

It is often challenging to follow fast surface adsorption processes with sufficient time resolution. Here we report a convenient UV-Vis spectrophotometry based method to study the fast kinetics of an archetypical surface process: the adsorption of MB on quartz. The test object was a commercial quartz cuvette. About 3.3% of the dye was adsorbed from a 34 μM solution at pH 7 in 10 min. Biphasic kinetics was observed for the depletion of MB under continuous stirring at 1000 rpm. A kinetic model was postulated for the interpretation of time resolved spectral changes. This model assumes the reversible adsorption of MB on the surface which is followed by the isomerization of the binding mode. The overall process is kinetically first order with respect to MB, thus dimer formation, which was previously proposed to be favored on quartz, can be ruled out. The experimental adsorption isotherm is consistent with the formation of an adsorption monolayer from single molecules. The UV-vis absorbance spectrum of adsorbed MB does not show any blue shift. With the simplest experimental setup, it is shown that the dimerization of MB is not exceptionally favored on quartz surface. © 2016 Elsevier Ltd. All rights reserved.

Bolyog-Nagy E.,Debrecen University | Udvardy A.,Debrecen University | Joo F.,Debrecen University | Joo F.,Mta Of Homogeneous Catalysis And Reaction Mechanisms Research Group | Katho A.,Debrecen University
Tetrahedron Letters | Year: 2014

A simple and efficient synthesis of amides by selective hydration of aromatic and aliphatic nitriles is described. The catalysts are prepared in situ from easily available Ru-precursors and ligands using water as the solvent. The most active catalyst, is obtained from [RuCl2(dmso)4] and benzylated 1,3,5-triaza-7-phosphaadamantane. Of the 16 substrates examined, 92-99% conversions of 14 nitriles were achieved in one hour at reflux temperature. © 2014 Elsevier Ltd. All rights reserved.

Lazar I.,Debrecen University | Kalmar J.,Mta Of Homogeneous Catalysis And Reaction Mechanisms Research Group | Peter A.,Technical University of Cluj Napoca | Szilagyi A.,Debrecen University | And 3 more authors.
Applied Surface Science | Year: 2015

Titania-silica composite aerogels with 16-29% Ti-content by the mass were synthesized by the sol-gel method from different Ti-precursors, and calcined at 500 °C. These aerogels are highly amorphous as no crystalline TiO2 phase can be detected in them by X-ray diffraction methods, and show the dominating presence of either mesopores or macropores. The incorporation of Ti into the silica structure is shown by the appearance of characteristic IR transitions of Si-O-Ti vibrations. The characteristic band-gap energies of the different aerogels are estimated to be between 3.6 and 3.9 eV from UV reflection spectra. Band-gap energy decreases with decreasing pore-size. When suspended in solution, even these highly amorphous aerogels accelerate the photodegradation of salicylic acid and methylene blue compared to simple photolysis. Kinetic experiments were conducted under illumination, and also in the dark to study the adsorption of the substrates onto the suspended aerogels. We assume that the fast in situ adsorption of the organic substrates mask the suspended aerogel particles from UV photons, which reduces the rate of photocatalysis. We managed to mathematically separate the parallel processes of photocatalysis and adsorption, and develop a simple kinetic model to describe the reaction system. © 2015 Elsevier B.V. All rights reserved.

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