Ändra sökning
Avgränsa sökresultatet
1 - 16 av 16
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 1.
    Fakhardji, Wissam
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Szabo, Peter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    El-Kader, M.S.A.
    Department of Engineering Mathematics and Physics, Faculty of Engineering, Cairo University, Giza, Egypt. Department of Physics, Faculty of Sciences and Humanity Studies, Huraimla, Shaqra University, Shaqra, Saudi Arabia.
    Haskopoulos, Anastasios
    Department of Chemistry, University of Patras, Patras, Greece.
    Maroulis, George
    Department of Chemistry, University of Patras, Patras, Greece.
    Gustafsson, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Collision-induced absorption in Ar–Kr gas mixtures: A molecular dynamics study with new potential and dipole data2019Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 151, nr 14, artikel-id 144303Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have implemented a scheme for classical molecular dynamics simulations of collision-induced absorption. The program has been applied to a gas mixture of argon (Ar) and krypton (Kr). The simulations are compared with accurate quantum dynamical calculations. The comparisons of the absorption coefficients show that classical molecular dynamics is correct within 10% for photon wave numbers up to 220 cm−1 at a temperature of 200 K for this system. At higher temperatures, the agreement is even better. Molecular dynamics accounts for many-body interactions, which, for example, give rise to continuous dimer formation and destruction in the gas. In this way, the method has an advantage compared with bimolecular classical (trajectory) treatments. The calculations are carried out with a new empirical Ar–Kr pair potential. This has been obtained through extensive analysis of experimental thermophysical and transport properties. We also present a new high level ab initio Ar–Kr potential curve for comparison, as well as ab initio interaction-induced dipole curves computed with different methods. In addition, the Ar–Kr polarizability and hyperpolarizability are reported. A comparison of the computed absorption spectra with an experiment taken at 300 K shows satisfactory agreement although a difference in absolute magnitude of 10%–15% persists. This discrepancy we attribute mainly to experimental uncertainty.

  • 2.
    Fehér, Klaudia
    et al.
    Department of Organic Chemistry University of Pannonia, Institute of Chemistry Egyetem, Veszprém, Hungary.
    Nagy, Eniko
    Department of Organic Chemistry University of Pannonia, Institute of Chemistry Egyetem, Veszprém, Hungary.
    Szabo, Peter
    Department of Analytical Chemistry University of Pannonia, Institute of Chemistry Egyetem, Veszprém, Hungary.
    Juzsakova, Tatjana
    University of Pannonia, Institute of Environmental Engineering Egyetem, Veszprém Hungary.
    Srankó, David
    Department of Surface Chemistry and Catalysis Hungarian Academy of Sciences, Centre for Energy Research, Budapest, Hungary.
    Gömöry, Ágnes
    Research Centre for Natural Sciences Hungarian Academy of Sciences, Budapest, Hungary.
    Kollár, Lazslo
    Department of Inorganic Chemistry and MTA-PTE Research Group for Selective Chemical Syntheses University of Pécs, Pécs, Hungary.
    Skoda-Földes, Rita
    Department of Organic Chemistry University of Pannonia, Institute of Chemistry Egyetem, Veszprém, Hungary.
    Heterogeneous azide–alkyne cycloaddition in the presence of a copper catalyst supported on an ionic liquid polymer/silica hybrid material2018Ingår i: Applied organometallic chemistry, ISSN 0268-2605, E-ISSN 1099-0739, Vol. 32, nr 6, artikel-id e4343Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Heterogeneous copper catalysts were prepared by the deposition of CuI on a hybrid material consisting of silica and a polymer with imidazolium moieties. The solid materials were characterised using solid‐phase NMR, Fourier transform infrared, Raman and X‐ray photoelectron spectroscopies and Brunauer–Emmett–Teller measurements. The formation of copper–carbene complexes was proved from Raman spectra and the results were supported by density functional theory calculations. The catalyst could be recycled efficiently with low loss of copper. Metal leaching was proved to be facilitated by the use of conditions typical for a homogeneous system (the presence of a polar solvent or the addition of a tertiary amine). Besides simple model reactions, the best catalyst was found to be suitable for the synthesis of triazoles of more elaborate structure, such as ferrocene or steroid derivatives.

  • 3.
    Gergely, Andras
    et al.
    Department of Physical Chemistry, Institute of Chemistry, University of Pannonia, Egyetem, Hungary .
    Szabó, Péter
    Department of General and Inorganic Chemistry, Institute of Chemistry, University of Pannonia, Egyetem, Hungary .
    Krojer, Antal
    Department of Inspection and Maintenance, Mol Nyrt., Olajmunkás, Hungary .
    Nagy, Bence
    Refining Research and Innovation, Mol Nyrt., Hungary .
    Kristof, Tamas
    Department of Physical Chemistry, Institute of Chemistry, University of Pannonia, Egyetem, Hungary .
    Hydrogen Sulfide Corrosion of Carbon and Stainless Steel Alloys in Mixtures of Renewable Fuel Sources under Co-Processing Conditions2018Ingår i: Modern Applied Science, ISSN 1913-1844, E-ISSN 1913-1852, Vol. 12, nr 4, s. 227-255Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Corrosion rates of steel alloys were investigated in gas oil and its mixture with waste cooking oil and animal waste lard over 1, 3, 7 and 21 days under desulfurizing condition. Co-processing conditions were attempted to simulate by batch-reactor experiment at temperatures between 200 and 300oC and pressures between 20 and 90 bar in the presence of 2 volume% hydrogen sulfide. Integral and differential corrosion rates were defined by weight losses. Intense sulfide corrosion of carbon steels was less impacted by the biomass sources. Thinner scales in gas oil was probably due to frequent cohesive failure, whereas thicker layers in biomass mixtures were allowed to form to afford limited physical protection. The high corrosion rate of low alloy steel with temperature over time is related to inefficient protection by the metal sulfide scales. Greater activation energy and enthalpy balance in the formation of activated complex is expected to reflect in thick cohesive scales. Loose layers and the less unfavorable entropy balance in the transition state did not lead to valuable barrier protection. High sulfide corrosion resistance of stainless steels is in chemical in nature markedly impacted by the biomass fuel sources and contributed especially by the acidic species. Corrosion rates increased with temperature by magnitude similar to those of carbon steels, which probably owes to the less unfavorable entropy and free energy balance between the initial and transition states of the reactants.

  • 4.
    Gergely, András
    et al.
    Department of Physical Chemistry, Institute of Chemistry, University of Pannonia.
    Locskai, Roland
    Department of Physical Chemistry, Institute of Chemistry, University of Pannonia.
    Szabo, Peter
    Krójer, Antal
    Department of Inspection and Maintenance.
    Kristóf, Tamás
    Department of Physical Chemistry, Institute of Chemistry, University of Pannonia.
    Hydrogen Sulphide Corrosion of Carbon and Stainless Steel Alloys Immersed in Mixtures of Renewable Fuel Sources and Tested Under Co-processing Conditions2016Ingår i: Hungarian Journal of Industry and Chemistry, ISSN 2450-5102, Vol. 44, nr 1, s. 55-70Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In accordance with modern regulations and directives, the use of renewable biomass materials as precursors for the production of fuels for transportation purposes is to be strictly followed. Even though, there are problems related to processing, storage and handling in wide range of subsequent uses, since there must be a limit to the ratio of biofuels mixed with mineral raw materials. As a key factor with regards to these biomass sources pose a great risk of causing multiple forms of corrosion both to metallic and non-metallic structural materials. To assess the degree of corrosion risk to a variety of engineering alloys like low-carbon and stainless steels widely used as structural metals, this work is dedicated to investigating corrosion rates of economically reasonable engineering steel alloys in mixtures of raw gas oil and renewable biomass fuel sources under typical co-processing conditions. To model a desulphurising refining process, corrosion tests were carried out with raw mineral gasoline and its mixture with used cooking oil and animal waste lard in relative quantities of 10% (g/g). Co-processing was simulated by batch-reactor laboratory experiments. Experiments were performed at temperatures between 200 and 300ºC and a pressure in the gas phase of 90 bar containing 2% (m3/m3) hydrogen sulphide. The time span of individual tests were varied between 1 and 21 days so that we can conclude about changes in the reaction rates against time exposure of and extrapolate for longer periods of exposure. Initial and integral corrosion rates were defined by a weight loss method on standard size of coupons of all sorts of steel alloys. Corrosion rates of carbon steels indicated a linear increase with temperature and little variation with composition of the biomass fuel sources. Apparent activation energies over the first 24-hour period remained moderate, varying between 35.5 and 50.3 kJ mol−1. Scales developed on carbon steels at higher temperatures were less susceptible to spall and detach. Nonetheless, moderate deceleration of corrosion rates as a function of time are due to the less coherent, frequently spalling and low compactness, higher porosity of the scales evolved at lower and higher temperatures, respectively. On the surface of high alloy steels, sulphide scales of an enhanced barrier nature formed during the induction periods and the layer formation mechanism was found to be assisted by the increasing temperature as initial reaction rates considerably decreased over time. Nevertheless, corrosion-related sulphide conversion of metals and mass loss of the high alloys are strongly affected by the composition of the biomass fuel sources especially animal waste lard. Thermal activation in the first 24 hours decreased from 68.9 to 35.2 kJ mol−1. A greater degree of failure to develop protective sulphide scales was experienced by changing to composition of the biomass fuel sources than the impact of thermal activation between a narrow temperature range at around 100ºC. In accordance with the literature, high free fatty acid contents lead to high corrosion rates accounted for direct corrosion of high alloy steels and assisted solubilisation of corrosion products. In addition, the pronounced acceleration of sulphide corrosion is connected to the diminishing inhibition effect of the sulphide scales

  • 5.
    Góger, Szabolcs
    et al.
    Department of General and Inorganic Chemistry, University of Pannonia. Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences.
    Szabo, Peter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Czakó, Gábor
    Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged.
    Lendvay, György
    Department of General and Inorganic Chemistry, University of Pannonia. Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Hungary.
    Flame Inhibition Chemistry: Rate Coefficients of the Reactions of HBr with CH3 and OH Radicals at High Temperatures Determined by Quasiclassical Trajectory Calculations2018Ingår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 32, nr 10, s. 10100-10105Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Reactions of HBr with radicals are involved in atmospheric chemistry and in the mechanism of operation of bromine-containing flame retardants. The rate coefficients for two such reactions, HBr + OH and HBr + CH3, are available from earlier experiments at near or below room temperature, relevant for atmospheric chemistry, and in this domain, the activation energy for both has been found to be negative. However, no experimental data are available at combustion temperatures. In this work, to provide reliable data needed for modeling the action of brominated flame suppressants, we used the quasiclassical trajectory (QCT) method in combination with high-level ab initio potential energy surfaces to evaluate the rate coefficients of the two title reactions at combustion temperatures. The QCT calculations have been validated by reproducing the experimental rate coefficients at room temperature. At temperatures between 600 and 3200 K, the QCT rate coefficients display positive activation energies. We recommend the following extended Arrhenius expressions to describe the temperature dependence of the thermal rate coefficients: k6 = (9.86 ± 2.38) × 10–16T(1.23±0.03) exp[(5.93 ± 0.33) kJ mol–1/RT] cm3 molecule–1 s–1 for the HBr + OH → H2O + Br reaction, and k–2 = (4.06 ± 2.72) × 10–18T(1.83±0.08) exp[(7.53 ± 0.18) kJ mol–1/RT] cm3 molecule–1 s–1 for the HBr + CH3 → CH4 + Br reaction. The latter is in very good agreement with the formula proposed by Burgess et al. [Burgess, D. R., Jr.; Babushok, V. I.; Linteris, G. T.; Manion, J. A. A Chemical Kinetic Mechanism for 2-Bromo-3,3,3-trifluoropropene (2-BTP) Flame Inhibition. Int. J. Chem. Kinet. 2015, 47, 533−619, DOI: 10.1002/kin.20923]. The conventional transition state theory has been tested against the rate data obtained by the QCT method and was found to overestimate not only the rate coefficients but also the activation energies

  • 6.
    Hegedűs, Péter
    et al.
    Department of General and Inorganic Chemistry, Institute of Chemistry, University of Pannonia, Hungary.
    Szabó-Bárdos, Erzsébet
    Department of General and Inorganic Chemistry, Institute of Chemistry, University of Pannonia, Hungary.
    Horváth, Ottó
    Department of General and Inorganic Chemistry, Institute of Chemistry, University of Pannonia, Hungary.
    Szabó, Péter
    Department of Analytical Chemistry, Institute of Chemistry, University of Pannonia, Hungary.
    Horváth, Krisztián
    Department of Analytical Chemistry, Institute of Chemistry, University of Pannonia, Hungary.
    Investigation of a TiO2 photocatalyst immobilized with poly(vinyl alcohol)2017Ingår i: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 284, s. 179-186Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Immobilization of TiO2 photocatalyst was realized with application of poly(vinyl alcohol) (PVA). However, these PVA-based foils were too instable to be used for photocatalytic water cleaning. Their stability could be significantly enhanced by a thermal treatment, but this procedure generated various water-soluble derivatives such as aldehydes, ketones, and aromatic species. Photocatalytic pre-treatment of the foils proved to be suitable to remove these products from the surface of the composite. After three subsequent pre-treating cycles of irradiation and rinsing, the PVA-TiO2 foil became applicable for photocatalytic degradation of Triton X-100, a widely used non-ionic detergent. The composite catalyst kept its stability and efficiency even after some cycles of re-usage, while its surface underwent a perceptible, although quantitatively negligible degradation.

  • 7.
    Papp, Mate
    et al.
    University of Pannonia, Institute of Chemistry, Department of Organic Chemistry, Hungary.
    Szabó, Péter
    University of Pannonia, Institute of Chemistry, Department of Analytical Chemistry, Hungary.
    Sranko, David
    Hungarian Academy of Sciences, Centre for Energy Research, Department of Surface Chemistry and Catalysis, Hungary.
    Skoda-Földes, R.
    University of Pannonia, Institute of Chemistry, Department of Organic Chemistry, Hungary.
    Solvent-free aminocarbonylation of iodobenzene in the presence of SILP-palladium catalysts2016Ingår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 6, nr 51, s. 45349-45356Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Heterogeneous palladium catalysts were prepared by the immobilisation of palladium on supported ionic liquid phases (SILP) obtained by physisorption or grafting. They were characterised by different techniques such as 13C CP MAS NMR, 31P CP MAS NMR, FT-IR, XPS and ICP. The catalysts were used efficiently under solvent-free conditions. They led to the formation of amide products with good to excellent selectivity. Recyclability at 5–10 bar CO pressure has also been demonstrated. The same reusable catalysts were proved to lead to the selective formation of double carbonylation products under higher pressure in DMF.

  • 8.
    Papp, Máte
    et al.
    Department of Organic Chemistry, Institute of Chemistry, University of Pannonia.
    Szabó, Péter
    Department of Analytical Chemistry, University of Pannonia.
    Srankó, Dávid
    Department of Surface Chemistry and Catalysis, Centre for Energy Research, Hungarian Academy of Sciences.
    Sáfrán, György
    Research Institute for Technical Physics and Materials Science, Hungarian Academy of Sciences.
    Kollár, L.
    Department of Inorganic Chemistry, MTA-PTE Research Group for Selective Chemical Syntheses, University of Pécs.
    Skoda-Földes, R.
    Department of Organic Chemistry, Institute of Chemistry, University of Pannonia.
    Mono- and double carbonylation of aryl iodides with amine nucleophiles in the presence of recyclable palladium catalysts immobilised on a supported dicationic ionic liquid phase2017Ingår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 7, nr 70, s. 44587-44597Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Silica modified with organic dicationic moieties proved to be an excellent support for palladium catalysts used in the aminocarbonylation of aryl iodides. By an appropriate choice of the reaction conditions, the same catalyst could be used for selective mono- or double carbonylations leading to amide and α-ketoamide products, respectively. The best catalyst could be recycled for at least 10 consecutive runs with a loss of palladium below the detection limit. By the application of the new support, efficient catalyst recycling could be achieved under mild reaction conditions (under low pressure and in a short reaction time). Palladium-leaching data support a mechanism with dissolution—re-precipitation of the active palladium species.

  • 9.
    Szabo, Peter
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Gustafsson, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    A surface-hopping method for semiclassical calculations of cross sectionsfor radiative association with electronic transitions2017Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 147, artikel-id 094308Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A semiclassical method based on surface-hopping techniques is developed to model the dynamics of radiative association with electronic transitions. It can be proven that this method is an extension of the established semiclassical formula used in the characterization of diatomic molecule-formation. Our method is tested for diatomic molecules. It gives the same cross sections as the former semiclassical formula but, contrary to the former method, it allows us to follow the fate of the trajectories after the emission of a photon. This means that we can characterize the rovibrational states of the stabilized molecules. Using semiclassical quantization, we can obtain quantum state-resolved cross sections or emission spectra for the radiative association process. The calculated semiclassical state-resolved spectra show general agreement with the result of quantum mechanical perturbation theory. Furthermore, our surface-hopping model is not only applicable for the description of radiative association but it can be used for semiclassical characterization of any molecular process where spontaneous emission occurs

  • 10.
    Szabo, Peter
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Gustafsson, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Formation of the NH molecule and its isotopologues through radiative association2019Ingår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 483, nr 3, s. 3574-3578Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The rate coefficients and the cross-sections for the formation of imidogen (NH) molecule (and its isotopologues: 15NH and ND) through radiative association are determined by employing quantum mechanical perturbation theory, classical Larmor formula, and Breit–Wigner theory. We suggest the radiative association process as possible route for NH production in diffuse interstellar clouds.

  • 11.
    Szabo, Peter
    et al.
    epartment of General and Inorganic Chemistry, Institute of Chemistry, University of Pannonia.
    Lendvay, Gyorgy
    epartment of General and Inorganic Chemistry, Institute of Chemistry, University of Pannonia.
    Horvath, Attila
    epartment of General and Inorganic Chemistry, Institute of Chemistry, University of Pannonia.
    Kovacs, Margit
    epartment of General and Inorganic Chemistry, Institute of Chemistry, University of Pannonia.
    The effect of the position of methyl substituents on photophysical and photochemical properties of [Ru(x,x[prime or minute]-dmb)(CN)4]2- complexes: experimental confirmation of the theoretical predictions2011Ingår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, nr 35, s. 16033-16045Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The molecular geometry, electronic structure and electronic spectra and the energy levels of the molecular orbitals responsible for the photophysical characteristics of a series of solvent tunable [Ru(x,x[prime or minute]-dmb)(CN)4]2- complexes (where x,x[prime or minute]-dmb = x,x[prime or minute]-dimethyl-2,2[prime or minute]-bipyridine) were calculated by density-functional theory-based quantum chemical methods, with the purpose of proposing for experimental study the best candidate for sensitizing electron- and energy transfer processes or for light induced structural changes in the molecule. The methods applied include geometry optimization using the B3LYP functional combination and various basis sets, time-dependent density functional theory with the B3LYP and PBE0 functionals, with and without explicit inclusion of coordinated solvent H2O molecules and the conductor-like polarizable continuum model for solvation. The accuracy of the theoretical predictions was tested by experiments: the model compounds have been synthesized and characterized by various spectroscopic methods, such as 1H-NMR, UV-Vis absorption and emission spectroscopy and by cyclic voltammetry. Excellent correlation was found between the theoretically calculated and the experimentally determined photophysical and photochemical characteristics. The electronic transition energies measured in water are superbly reproduced by TD-PBE0 and well by TD-B3LYP, but the performance of both functionals is worse if the solvent is acetonitrile.

  • 12.
    Szabo, Peter
    et al.
    Department of General and Inorganic Chemistry, Institute of Chemistry, University of Pannonia.
    Lendvay, György
    Department of General and Inorganic Chemistry, Institute of Chemistry, University of Pannonia.
    A Quasiclassical Trajectory Study of the Reaction of H Atoms with O2(1Δg)2015Ingår i: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 119, nr 28, s. 7180-7189Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The kinetic and dynamic characteristics of the reaction of H atoms with electronically excited O2 were studied using the quasiclassical trajectory (QCT) method and the potential energy surface of Li et al. (J. Chem. Phys. 2010, 133, 144306−144314). The reaction takes place via a deep potential well that can be entered by climbing a barrier in the reactant valley and can be left without a barrier on the product side. In this reaction, the basic assumptions of statistical rate theories are not fulfilled: (i) 80% of the trajectories cross the barrier region twice and are nonreactive; (ii) the energy is not equilibrated in the HO2 potential well. The QCT cross sections agree well with those from the existing exact quantum-mechanical data and extend them to vib-rotationally excited reactants. The thermal rate coefficients agree well with measurements of pure reactive quenching of O2(1Δg) and are lower than those involving both reactive and electronic quenching. The temperature dependence is described as k2 = 5.81 × 10–16 T1.45 exp(−2270/T) cm3 molecule–1 s–1. On the basis of a comparison of the QCT data with the two kinds of experiments, we estimate that electronic quenching is faster than reaction by a factor of about 10 at low and 2 at high flame temperatures.

  • 13.
    Szabo, Peter
    et al.
    Department of General and Inorganic Chemistry, Institute of Chemistry, University of Pannonia.
    Lendvay, György
    Department of General and Inorganic Chemistry, Institute of Chemistry, University of Pannonia.
    Dynamics of Complex-Forming Bimolecular Reactions: A Comparative Theoretical Study of the Reactions of H Atoms with O2(3Σg–) and O2(1Δg)2015Ingår i: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 119, nr 50, s. 12485-12497Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The atomic-level mechanism of the reaction of H atoms with triplet and singlet molecular oxygen, H(2S) + O2(3Σg–) → O(3P) + OH(2Πg) (R1) and H(2S) + O2(1Δg) → O(3P) + OH(2Πg) (R2) is analyzed in terms of the topology of the potential energy surfaces (PES) of the two reactions. Both PES exhibit a deep potential well corresponding to the ground and first excited electronic state of HO2. The ground-state reaction is endothermic with no barrier on either side of the well; the excited-state reaction is exothermic with a barrier in the entrance valley of the PES. The differences of the PES are manifested in properties such as the excitation functions, which show reaction R1 to be much slower and the effect of rotational excitation on reactivity, which speeds up reaction R1 and has little effect on R2. Numerous common dynamics features arise from the presence of the deep potential well on the PES. Such are the significant role of isomerization (for example, 90% of reactive collisions in R2 involve at least one H atom transfer from one of the O atoms to the other in reaction R2), which is shown to give rise to a significant rotational excitation of the product OH radicals. Common is the significant sideways scattering of the products that originates from collisions in propeller-type arrangements induced by the presence of two bands of acceptance around the O2 molecule. The HO2 complex in both reactions proves to behave nonstatistically, with signatures of the dynamics in lifetime distributions, angular distributions, opacity functions, and product quantum-state distributions.

  • 14.
    Szabo, Peter
    et al.
    Department of Analytical Chemistry, University of Pannonia.
    Zsirka, Balázs
    Institute of Environmental Engineering, University of Pannonia.
    Fertig, Dávid
    Department of Analytical Chemistry, University of Pannonia.
    Horváth, Erzsébet
    Institute of Environmental Engineering, University of Pannonia.
    Csizmadia, Tamás
    Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University.
    Kristóf, János
    Institute of Environmental Engineering, University of Pannonia.
    Delaminated kaolinites as potential photocatalysts: Tracking degradation of Na-benzenesulfonate test compound adsorbed on the dry surface of kaolinite nanostructures2017Ingår i: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 287, nr Supplement C, s. 37-44Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Abstract Based on their bandgap values, kaolins can have semiconductive and photocatalytic properties enabling them to use as potential photocatalysts. Kaolinite nanostructures (Knano) and silver-coated kaolinite nanohybrids (Knano(Ag)) were made of ordered (Hinkley Index, HI=1.4) and disordered (HI=0.3) kaolins via intercalation/deintercalation. The book-type kaolin built up from tetrahedral(T)-octahedral(O) double layers has very low photocatalytic activity. At the same time the nanostructures made of individual TO layers show photochemical activity in spite of the fact that their bandgap values are comparable to those of the book-type ones. The presence of Ag on the surface significantly reduced the bandgap and shifted the excitation wavelength towards the visible range. This phenomenon supports the supposition that kaolinite has some semiconductive character. This work presents the connection between photocatalytic activity and morphology for the first time. The surface activity of kaolinite nanostructures and their Ag-hybrids was studied through the decomposition of sodium-benzenesulfonate (BS) test compound with attenuated total reflection Fourier transform infrared spectroscopy (FT-IR/ATR). BS decomposition can be detected on the Knano surface but with low efficiency. The presence of silver can significantly improve the mineralization efficiency. No correlation was found between the activity and the quantity of Ti and Fe contaminants and the amount of Ag on the surface. However, the activity could be correlated with the order-dependent morphology (mixture of semi-hexagonal and nanoscroll-type structures), the pore size and with the increase of the surface coverage.

  • 15.
    Urbán, Béla
    et al.
    University of Pannonia, Institute of Chemistry, Department of Organic Chemistry, Egyetem u, Hungary.
    Szabó, Péter
    University of Pannonia, Institute of Chemistry, Department of Analytical Chemistry, Egyetem u, Hungary.
    Srankó, Dávid
    Hungarian Academy of Sciences, Centre for Energy Research, Department of Surface Chemistry and Catalysis, Hungary.
    Sáfrán, György
    Hungarian Academy of Sciences, Research Institute for Technical Physics and Materials Science, Hungary.
    Kollár, László
    University of Pécs, Department of Inorganic Chemistry and MTA-PTE Research Group for Selective Chemical Syntheses, Hungary.
    Skoda-Földes, Rita
    University of Pannonia, Institute of Chemistry, Department of Organic Chemistry, Egyetem u, Hungary.
    Double carbonylation of iodoarenes in the presence of reusable palladium catalysts immobilised on supported phosphonium ionic liquid phases2018Ingår i: Molecular Catalysis, ISSN 2468-8231, Vol. 445, s. 195-205Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The first heterogeneous carbonylation reaction carried out with palladium catalysts immobilised on phosphonium ion modified silica supports is reported. The supported ionic liquid phases were characterised by solid state NMR and FT-IR measurements. The presence of the phosphonium ions on the surface made it possible to carry out double carbonylation in apolar toluene efficiently that resulted in reduced metal leaching. The introduction of dicationic moieties on the solid support has been proved to lead to a further increase in catalyst stability. The catalysts were proved to produce α-ketoamide products with excellent selectivity in the carbonylation of iodoarenes with aliphatic amines while monocarbonylation was the only reaction observed with aniline derivatives. The catalysts could be recycled and used in at least 10 subsequent runs under optimised conditions.

  • 16.
    Zsirka, Balázs
    et al.
    University of Pannonia, Institute of Environmental Engineering, Hungary.
    Horváth, Erzsébet
    University of Pannonia, Institute of Environmental Engineering, Hungary.
    Szabó, Péter
    University of Pannonia, Department of Analytical Chemistry, Hungary.
    Juzsakova, Tatjána
    University of Pannonia, Institute of Environmental Engineering, Hungary.
    Szilágyi, Róbert K.
    Department of Chemistry and Biochemistry, Montana State University, USA.
    Fertig, Dávid
    University of Pannonia, Department of Analytical Chemistry, Hungary.
    Makó, Éva
    University of Pannonia, Institute of Materials Engineering, Hungary.
    Varga, Tamás
    University of Szeged, Department of Applied and Environmental Chemistry, Hungary.
    Kónya, Zoltán
    University of Szeged, Department of Applied and Environmental Chemistry, Hungary; MTA-SZTE Reaction Kinetics and Surface Chemistry Research Group, Hungary .
    Kukovecz, Ákos
    University of Szeged, Department of Applied and Environmental Chemistry, Hungary; MTA-SZTE “Lendület” Porous Nanocomposites Research Group, Hungary.
    Kristóf, János
    University of Pannonia, Department of Analytical Chemistry, Hungary.
    Thin-walled nanoscrolls by multi-step intercalation from tubular halloysite-10 Å and its rearrangement upon peroxide treatment2017Ingår i: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 399, s. 245-254Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Surface modification of the halloysite-10 Å mineral with tubular morphology can be achieved by slightly modified procedures developed for the delamination of kaolinite minerals. The resulting delaminated halloysite nanoparticles have unexpected surface/morphological properties that display, new potentials in catalyst development. In this work, a four-step intercalation/delamination procedure is described for the preparation of thin-walled nanoscrolls from the multi-layered hydrated halloysite mineral that consists of (1) intercalation of halloysite with potassium acetate, (2) replacement intercalation with ethylene glycol, (3) replacement intercalation with hexylamine, and (4) delamination with toluene. The intercalation steps were followed by X-ray diffraction, transmission electron microscopy, N2adsorption-desorption, thermogravimetry, and infrared spectroscopy. Delamination eliminated the crystalline order and the crystallite size along the ‘c’-axis, increased the specific surface area, greatly decreased the thickness of the mineral tubes to a monolayer, and shifted the pore diameter toward the micropore region. Unexpectedly, the removal of residual organics from intercalation steps adsorbed at the nanoscroll surface with a peroxide treatment resulted in partial recovery of crystallinity and increase of crystallite size along the ‘c’-crystal direction. The d(001) value showed a diffuse pattern at 7.4–7.7 Å due to the rearrangement of the thin-walled nanoscrolls toward the initial tubular morphology of the dehydrated halloysite-7 Å mineral.

1 - 16 av 16
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf