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X-Ray Spectrometry     Hybrid Journal   (Followers: 9)
Zeitschrift für Naturforschung B : A Journal of Chemical Sciences     Open Access   (Followers: 1)

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Journal Cover Kinetics and Catalysis
  [SJR: 0.317]   [H-I: 23]   [3 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1608-3210 - ISSN (Online) 0023-1584
   Published by Springer-Verlag Homepage  [2335 journals]
  • Dissociation energies of O–H bonds in 3-pyridinols
    • Authors: T. G. Denisova; E. T. Denisov
      Pages: 723 - 730
      Abstract: Abstract The O−H bond dissociation energy (D O−H) has been estimated for 20 substituted 3-pyridinols and a substituted 3-pyrimidinol from experimental kinetic data by the intersecting parabolas method using α-tocopherol and 4-methoxyphenol as reference compounds. The following D O−H values (kJ/mol) have been obtained: 363.7 for 3-pyridinol, 365.3 for 2-alkyl-3-pyridinols (five compounds), 358.8 for 2-alkyl-6-methyl-3-pyridinols (six compounds), 378.1 for 5-benzyl-3-pyridinol, 353.2 for 2,4,6-trimethyl-3-pyridinol, 340.9 for 2-benzyl-6-methoxy-3-pyridinol, 345.8 for 2,6-dimethoxy-5-benzyl-3-pyridinol, 381.7 for 2-ethyl-4-nitro-6-methyl-3-pyridinol, 376.8 for 2-isopropyl-4-nitro-6-methyl-3-pyridinol, 318.3 for 2,4-dimethyl-6-dimethylamino-3-pyridinol, 357.3 for mexidol, and 322.2 for 2,4-dimethyl-6-dimethylamino-3-pyrimidinol. The substituent effect on the O−H bond dissociation energy in 3-pyridinols is considered. The stabilization energies of pyridinoxyl and phenoxyl radicals are compared. The activation energies and rate constants have been calculated for a series of reactions of various radicals with 3-pyridinols.
      PubDate: 2016-11-01
      DOI: 10.1134/s0023158416050086
      Issue No: Vol. 57, No. 6 (2016)
       
  • Benefits of n -butanol, as a biofuel, in reducing the levels of soot
           precursors issued from the combustion of benzene flames
    • Authors: Y. Rezgui; M. Guemini
      Pages: 731 - 737
      Abstract: Abstract Although oxygenated fuel additives are effective in reducing soot emissions, the extent to which molecular structure of the oxygenate plays a role in soot reduction has remained unclear and controversial. To gain a deeper insight in this field, a detailed chemical kinetic modeling approach was used to examine the phenomenon of suppression of sooting by the addition of oxygenated hydrocarbon species to the fuel. For this task, the PREMIX code in conjunction with Chemkin II and models resulting from the merging of validated kinetic schemes describing the oxidation of the components of the n-butanol-benzene mixtures were used to investigate the effect of n-butanol addition on the formation−depletion of acetylene recognized as soot precursor in flames under fuel-rich conditions. The first part of this study treats the dependence of the soot precursor amounts on n-butanol percentage in the fuel mixture, whereas the second part defines the key reaction mechanisms responsible for the observed reduction in C2H2 and consequently in polycyclic aromatic hydrocarbons and soot amounts induced by the oxygenate additive. The principal objective of the current study was to obtain fundamental understanding of the mechanisms through which the oxygenate compound affects the soot precursor amounts. The modeling results indicated that there was a dramatic decrease in the acetylene peak height with the addition of the oxygenated addtitive. This finding was found to be due to the increase in the C2H2 consumption rates induced by n-butanol addition. Finally, the modeling results provided evidence that n-butanol played a role in changing acetylene formation mechanism by enhancing the role of C3H4P, C3H4 and aC3H5 and by eliminating the role of C6H4, C5H5, C5H6, H2CCCCH, C4H2, C5H4O, C2H, CHCHCHO, H2C4O and C4H4.
      PubDate: 2016-11-01
      DOI: 10.1134/s0023158416060136
      Issue No: Vol. 57, No. 6 (2016)
       
  • Inhibition of the photoinduced ignition of chloromethane–chlorine
           mixtures by oxygen
    • Authors: I. R. Begishev; A. K. Belikov; I. S. Nikitin
      Pages: 738 - 741
      Abstract: Abstract The introduction of small amounts of oxygen inhibits the photoinduced ignition of chloromethane–chlorine mixtures. This is accompanied by an increase in the induction period and a decrease in the degree of heating of the reaction mixture. After the consumption of the entire inhibitor, the photochlorination reaction takes place again in the thermal explosion regime but with a lower degree of heating. In the dependence of the mixture temperature on the oxygen concentration, criticality is not pronounced. With an increasing concentration of oxygen, its effect on the induction period weakens.
      PubDate: 2016-11-01
      DOI: 10.1134/s002315841606001x
      Issue No: Vol. 57, No. 6 (2016)
       
  • Kinetics and mechanism of diethyl sulfide oxidation by sodium peroxoborate
           in aqueous solutions
    • Authors: V. L. Lobachev; L. M. Dyatlenko; M. Yu. Zubritskii
      Pages: 742 - 749
      Abstract: Abstract The kinetics of diethyl sulfide (Et2S) oxidation by aqueous sodium peroxoborate (Na2[В2(О2)2(ОН)4]) solutions in a wide acidity range (from [HClO4] = 1 mol/L to рН 12) has been studied using a kinetic distribution method. The kinetic data together with the results of 11B NMR spectroscopy demonstrate that the monoperoxoborate B(O2H) 3 - (OH) and diperoxoborate B(O2H)2(OH) 2 - anions are the active species in Et2S oxidation by sodium peroxoborate at рН 8–12. It is assumed that, at a high acidity of the medium ([HClO4] = 0.05–1.0 mol/L), peroxoboric acid (ОН)2ВООН or its protonated form (OH)2BOOH 2 + are direct reactants along with Н2О2 and HOOH 2 + .
      PubDate: 2016-11-01
      DOI: 10.1134/s0023158416060094
      Issue No: Vol. 57, No. 6 (2016)
       
  • Autocatalysis by the nitroxyl radical in the cyclic mechanism of chain
           termination in polymer oxidation
    • Authors: E. T. Denisov
      Pages: 750 - 757
      Abstract: The activation energy and rate constant of the reaction between the nitroxyl radical and N-alkoxyamine as a concerted abstraction–fragmentation reaction have been calculated using the intersecting parabolas model. This reaction proceeds fairly rapidly and leads to nitroxyl radical autoregeneration as a result of the following consecutive reactions:AmO∙ + AmOR → AmOH + >C=O + Am∙, RO 2 ∙ + AmOH → ROOH + AmO∙, Am∙+ O2 → Am 2 ∙ , and 2AmO 2 ∙ → 2AmO∙ + O2. Thus, the nitroxyl radical is an effective radical catalyst for its own regeneration from N-alkoxyamine. The rates of regeneration of the nitroxyl radical from its N-alkoxyamine under the action of alkyl, alkoxyl, peroxyl, nitroxyl, and hydroperoxyl radicals under conditions of polypropylene oxidation inhibited by the nitroxyl radical are compared. It is demonstrated that only peroxyl, hydroperoxyl, and nitroxyl radicals are involved in AmO∙ regeneration from AmOR.
      PubDate: 2016-11-01
      DOI: 10.1134/s0023158416060057
      Issue No: Vol. 57, No. 6 (2016)
       
  • Mechanism of 5-amino-6-methyluracil-inhibited oxidation of organic
           compounds
    • Authors: R. A. Nasibullina; L. R. Yakupova; R. L. Safiullin
      Pages: 758 - 767
      Abstract: Abstract Based on experimental and theoretical data obtained in the mechanism study of the 5-amino-6-methyluracil-inhibited radical chain oxidation of 1,4-dioxane, a scheme for the process is proposed. A kinetic analysis of the scheme has been performed to obtain an equation describing the regularities of oxygen consumption that agree with the experimental data and provide evidence in favor of the chain consumption of the inhibitor under certain conditions. The composition of resulting products confirms the proposed mechanism.
      PubDate: 2016-11-01
      DOI: 10.1134/s0023158416060100
      Issue No: Vol. 57, No. 6 (2016)
       
  • Hybridized advanced oxidation processes involving UV/H 2 O 2 /S 2 O 8 2-
           for photooxidative removal of p -nitrophenol in an annular continuous-flow
           photoreactor
    • Authors: Morteza Mohammadzadeh; Mohammad A. Behnajady; Hamed Eskandarloo
      Pages: 768 - 775
      Abstract: Abstract In this paper, photooxidative removal of p-nitrophenol (PNP) as a model organic pollutant was investigated in the presence of UV/inorganic oxidants system in an annular continuous-flow photoreactor. The aim of this study was to evaluate the photooxidative efficiency of hybrid oxidant system including persulfate (UV/H2O2/S2O 8 2- ) and hydrogen peroxide (H2O2), under UV–C light irradiation. The effects of operational variables including UV/H2O2/S2O 8 2- and H2O2 concentrations, the initial PNP concentration, and residence time on the removal efficiency of UV/H2O2/H2O2/S2O 8 2- system were studied. It was found that the operational variables affected the removal efficiency of UV/H2O2/H2O2/S2O 8 2- system. Operating conditions were optimized using response surface methodology (RSM). Simulation approach showed that the predicted values of removal efficiency are in good agreement with the experimental results with a correlation coefficient (R 2) of 0.95. Optimization results showed that the maximum degree of removal (98%) was achieved by using the UV/H2O2/H2O2/S2O 8 2- system under the following operation conditions: concentration of H2O2 = 10 mmol/L, concentration of UV/H2O2/S2O 8 2- = 10 mmol/L, initial concentration of PNP = 35 mg/L, and residence time = 8 min. The obtained results clearly demonstrated that RSM is one of the useful and cost-effective methods for modeling and optimizing the efficiency of UV/H2O2/UV/H2O2/S2O 8 2- system.
      PubDate: 2016-11-01
      DOI: 10.1134/s0023158416060021
      Issue No: Vol. 57, No. 6 (2016)
       
  • Zeolite ZSM-5 containing copper ions: The effect of the copper salt anion
           and NH 4 OH/Cu 2+ ratio on the state of the copper ions and on the
           reactivity of the zeolite in DeNO x
    • Authors: S. A. Yashnik; Z. R. Ismagilov
      Pages: 776 - 796
      Abstract: Abstract Isotherms of copper cation sorption by H-ZSM-5 zeolite from aqueous and aqueous ammonia solutions of copper acetate, chloride, nitrate, and sulfate are considered in terms of Langmuir’s monomolecular adsorption model. Using UV-Vis diffuse reflectance spectroscopy, IR spectroscopy, and temperatureprogrammed reduction with hydrogen and carbon monoxide, it has been demonstrated that the electronic state of the copper ions is determined by the ion exchange and heat treatment conditions. The state of the copper ions has an effect on the redox properties and reactivity of the Cu-ZSM-5 catalysts in the selective catalytic reduction (SCR) of NO with propane and in N2O decomposition. The amount of Cu2+ that is sorbed by zeolite H-ZSM-5 from aqueous solution and is stabilized as isolated Cu2+ cations in cationexchange sites of the zeolite depends largely on the copper salt anion. The quantity of Cu(II) cations sorbed from aqueous solutions of copper salts of strong acids is smaller than the quantity of the same cations sorbed from the copper acetate solution. When copper chloride or sulfate is used, the zeolite is modified by the chloride or sulfate anion. Because of the presence of these anions, the redox properties and nitrogen oxides removal (DeNO x ) efficiency of the Cu-ZSM-5 catalysts prepared using the copper salts of strong acids are worse than the same characteristics of the sample prepared using the copper acetate solution. The addition of ammonia to the aqueous solutions of copper salts diminishes the copper salt anion effect on the amount of Cu(II) sorbed from these solutions and hampers the nonspecific sorption of anions on the zeolite surface. As a consequence, the redox and DeNO x properties of Cu-ZSM-5 depend considerably on the NH4OH/Cu2+ ratio in the solution used in ion exchange. The aqueous ammonia solutions of the copper salts with NH4OH/Cu2+ = 6–10 stabilize, in the Cu-ZSM-5 structure, Cu2+ ions bonded with extraframework oxygen, which are more active in DeNO x than isolated Cu2+ ions (which form at NH4OH/Cu2+ = 30) or nanosized CuO particles (which form at NH4OH/Cu2+ = 3).
      PubDate: 2016-11-01
      DOI: 10.1134/s0023158416060161
      Issue No: Vol. 57, No. 6 (2016)
       
  • Role of anionic vacancies in lithium fluoride in the catalytic oxidation
           of carbon monoxide on the surface of the Au/LiF/Mo(110) system
    • Authors: I. V. Silaev; S. A. Khubezhov; I. V. Tvauri; G. S. Grigorkina; A. G. Kaloeva; O. G. Ashkhotov; D. Sekiba; S. Ogura; K. Fukutani; T. T. Magkoev
      Pages: 797 - 802
      Abstract: Abstract The oxidation of carbon monoxide molecules on the surface of gold nanoclusters formed on a lithium fluoride film has been investigated by IR spectroscopy and temperature-programed reaction. The CO oxidation rate is much higher in the case of gold clusters produced on the surface of a LiF film enriched with anionic vacancies (F-centers). This is due to the fact that the gold clusters bonded to F-centers of the substrate differ in electronic state from the clusters that are not bonded to F-centers.
      PubDate: 2016-11-01
      DOI: 10.1134/s0023158416060148
      Issue No: Vol. 57, No. 6 (2016)
       
  • Conversion of ethanol into linear primary alcohols on gold, nickel, and
           gold–nickel catalysts
    • Authors: A. V. Chistyakov; P. A. Zharova; M. V. Tsodikov; S. A. Nikolaev; I. N. Krotova; D. I. Ezzhelenko
      Pages: 803 - 811
      Abstract: Abstract The direct conversion of ethanol into the linear primary alcohols C n H2n+1OH (n = 4, 6, and 8) in the presence of the original mono- and bimetallic catalysts Au/Al2O3, Ni/Al2O3, and Au–Ni/Al2O3 was studied. It was established that the rate and selectivity of the reaction performed under the conditions of a supercritical state of ethanol sharply increased in the presence of Au–Ni/Al2O3. The yield of target products on the bimetallic catalyst was higher by a factor of 2–3 than that reached on the monometallic analogs. Differences in the catalytic behaviors of the Au, Ni, and Au–Ni systems were discussed with consideration for their structure peculiarities and reaction mechanisms.
      PubDate: 2016-11-01
      DOI: 10.1134/s0023158416060045
      Issue No: Vol. 57, No. 6 (2016)
       
  • Conversion of bio-oxygenates into hydrocarbons in the presence of a
           commercial Pt–Re/Al 2 O 3 catalyst
    • Authors: A. V. Chistyakov; P. A. Zharova; A. E. Gekhman; V. V. Kriventsov; M. V. Tsodikov
      Pages: 812 - 820
      Abstract: Abstract It was found that the preliminarily reduced commercial platinum–rhenium catalyst PR-71 exhibited high activity in the conversion of ethanol into C4–C12 olefins and in the cross-condensation reactions of ethanol with glycerol, acetone, n-propanol, and isopropanol. Acetone and glycerol exhibited the highest reactivity in the cross-condensation reactions; this manifested itself in an increase in the total yield of the target fraction of C4–C12 hydrocarbons and in a more than 10-fold increase in the yield of products containing the odd numbers of carbon atoms, as compared with the conversion of individual ethanol. The structural studies performed by extended X-ray absorption fine structure (EXAFS) spectroscopy and transmission electron microscopy showed that the high selectivity of PR-71 can be caused by the formation of bimetallic Pt–Re and Pt–Al clusters in the course of the prolonged preliminary reduction of the catalyst.
      PubDate: 2016-11-01
      DOI: 10.1134/s0023158416060033
      Issue No: Vol. 57, No. 6 (2016)
       
  • Effect of the ligand nature in cobalt complexes on the selectivity of the
           reaction of carbon dioxide and propylene oxide
    • Authors: O. M. Chukanova; G. P. Belov
      Pages: 821 - 825
      Abstract: Abstract The reaction of carbon dioxide with propylene oxide in the presence of the (salen)CoCl or (TPP)CoCl (salen = bis(3,5-di-tert-butyl-salicylidene)-1,2-diaminocyclohexane, TPP = 5,10,15,20-tetraphenylporphyrin) catalyst and the PPNCl (bis(triphenylphosphine)iminium chloride) cocatalyst has been carried out at 20–60°С and a СО2 pressure of 0.6 MPa to investigate the effect of the ligand nature on the reaction rate and selectivity. The change in the reaction rate and selectivity in relation to the temperature and cocatalyst/catalyst ratio has been studied. The activation energy of the copolymerization of СО2 with propylene oxide catalyzed by the (salen)CoCl complex have been obtained.
      PubDate: 2016-11-01
      DOI: 10.1134/s0023158416050074
      Issue No: Vol. 57, No. 6 (2016)
       
  • Oxidation of a platinum foil with nitrogen dioxide
    • Authors: A. V. Kalinkin; M. Yu. Smirnov; V. I. Bukhtiyarov
      Pages: 826 - 830
      Abstract: Abstract The oxidation of a polycrystalline platinum foil by nitrogen dioxide at an NO2 pressures of 10–6–10–4 mbar and a temperature of 525 K has been investigated by X-ray photoelectron spectroscopy (XPS). Under these conditions, the platinum oxides PtO and Pt3O4 form on the foil surface. A comparison between the data obtained in this study and the data on the oxidation of platinum nanoparticles suggests a hypothesis as to the causes of the size effect in the oxidation of NO over platinum catalysts.
      PubDate: 2016-11-01
      DOI: 10.1134/s0023158416060069
      Issue No: Vol. 57, No. 6 (2016)
       
  • Effect of the composition of the reaction atmosphere on the thermal
           stability of highly dispersed gold particles on an oxide support (Au/Al 2
           O 3 system)
    • Authors: M. Yu. Smirnov; E. I. Vovk; A. V. Kalinkin; V. I. Bukhtiyarov
      Pages: 831 - 839
      Abstract: Abstract Metal gold particles were supported onto the surface of aluminum oxide by physical vapor deposition. The effects of thermal treatments at 30−800°C both in a vacuum and in an atmosphere of O2 (5 mbar), CO (5 mbar), or a mixture of CO + O2 (5 mbar of each) on the samples of Au/Al2O3 were studied by X-ray photoelectron spectroscopy. An increase in the Au4f line intensity in the course of gold deposition was accompanied by a shift of this line toward smaller binding energy. Upon the supporting of a maximum quantity of gold, the binding energy E b(Au4f 7/2) became smaller than the value characteristic of the bulk metal. It was hypothesized that this can be explained by the formation of negatively charged Auδ− particles due to electron density transfer from the support to the particles of gold. In the course of the heating of Au/Al2O3 in a vacuum or in a reaction atmosphere, the agglomeration of small gold particles occurred; this fact manifested itself in a decrease in the atomic ratio [Au]/[Al]. In all of the atmospheres, the Au particles supported on Al2O3 exhibited high thermal stability; considerable changes in the ratio [Au]/[Al] were observed only at temperatures higher than 600°C.
      PubDate: 2016-11-01
      DOI: 10.1134/s002315841606015x
      Issue No: Vol. 57, No. 6 (2016)
       
  • Synthesis and catalytic activity of porous polymer containing ionic liquid
           structures
    • Authors: Junqiao Li; Wei Lu; Weifeng Li; Xuezheng Liang
      Pages: 840 - 846
      Abstract: Abstract A novel porous polymer containing ionic liquid (IL) structures was synthesized via quternization and condensation of 4-vinylpyridine and p-xylylene dichloride. The ionic liquid structures were incorporated in the polymeric framework and for this reason bulky IL molecules can hardly block pores and neutralize active sites. The polymer shows a high BET surface area and easily accessible active sites. Catalytically the polymer is very active in Michael additions with averaged yields over 96.0% achieved after short reaction times. The high BET surface, remarkable activity, operational simplicity, wide applicability and improved stability are the key properties of the polymer.
      PubDate: 2016-11-01
      DOI: 10.1134/s0023158416060082
      Issue No: Vol. 57, No. 6 (2016)
       
  • Catalysts with platinum–palladium nanoparticles on polymer matrix
           supports
    • Authors: M. V. Lebedeva; N. A. Yashtulov; V. R. Flid
      Pages: 847 - 852
      Abstract: Abstract The platinum–palladium/Nafion metal–polymer nanocomposites were synthesized by the chemical reduction of ions in the aqueous organic solutions of inverted microemulsions. The functional characteristics of the nanocomposites were studied by cyclic voltammetry, atomic force microscopy, and scanning electron microscopy. The nanocatalysts obtained exhibited high activity in the reactions of oxygen reduction and hydrogen oxidation. The influence of synthesis conditions on the catalytic activity of the metal–polymer nanocomposites was studied.
      PubDate: 2016-11-01
      DOI: 10.1134/s0023158416060070
      Issue No: Vol. 57, No. 6 (2016)
       
  • Catalytic properties of nanostructured Pd–Ag catalysts in the
           liquid-phase hydrogenation of terminal and internal alkynes
    • Authors: A. V. Rassolov; P. V. Markov; G. O. Bragina; G. N. Baeva; I. S. Mashkovskii; I. A. Yakushev; M. N. Vargaftik; A. Yu. Stakheev
      Pages: 853 - 858
      Abstract: Abstract A comparative catalytic study of Pd–Ag bimetallic catalysts and the commercial Lindlar catalyst (Pd–Pb/CaCO3) has been carried out in the hydrogenation of phenylacetylene (PA) and diphenylacetylene (DPA). The Pd–Ag catalysts have been prepared using the heterobimetallic complex PdAg2(OAc)4(HOAc)4 supported on MgAl2O4 and aluminas (α-Al2O3 and γ-Al2O3). Physicochemical studies have demonstrated that the reduction of supported Pd–Ag complex with hydrogen results in homogeneous Pd–Ag nanoparticles. Equal in selectivity to the Lindlar catalyst, the Pd–Ag catalysts are more active in DPA hydrogenation. The synthesized Pd–Ag catalysts are active and selective in PA hydrogenation as well, but the unfavorable ratio of the rates of the first and second stages of the process makes it difficult to kinetically control the reaction. The most promising results have been obtained for the Pd–Ag2/α-Al2O3 catalyst. Although this catalyst is less active, it is very selective and allows efficient kinetic control of the process to be carried out owing to the fact that, with this catalyst, the rate of hydrogenation of the resulting styrene is much lower than the rate of hydrogenation of the initial PA.
      PubDate: 2016-11-01
      DOI: 10.1134/s0023158416060124
      Issue No: Vol. 57, No. 6 (2016)
       
  • Formation of Pd–Ag nanoparticles in supported catalysts based on the
           heterobimetallic complex PdAg 2 (OAc) 4 (HOAc) 4
    • Authors: A. V. Rassolov; P. V. Markov; G. O. Bragina; G. N. Baeva; D. S. Krivoruchenko; I. S. Mashkovskii; I. A. Yakushev; M. N. Vargaftik; A. Yu. Stakheev
      Pages: 859 - 865
      Abstract: Abstract The formation of Pd–Ag nanoparticles deposited from the heterobimetallic acetate complex PdAg2(OAc)4(HOAc)4 on α-Al2O3, γ-Al2O3, and MgAl2O4 has been investigated by high-resolution trans-mission electron microscopy, temperature-programmed reduction, and IR spectroscopy of adsorbed CO. The reduction of PdAg2(OAc)4(HOAc)4 supported on γ-Al2O3 and MgAl2O4 takes place in two steps (at 15–245 and 290–550°C) and yields Pd–Ag particles whose average size is 6–7 nm. The reduction of the Pd–Ag catalyst supported on α-Al2O3 occurs in a much narrower temperature range (15–200°C) and yields larger nanoparticles (~10–20 nm). The formation of Pd–Ag alloy nanoparticles in all of the samples is demonstrated by IR spectroscopy of adsorbed CO, which indicates a marked weakening of the absorption band of the bridged form of adsorbed carbon monoxide and a >30-cm–1 bathochromic shift of the linear adsorbed CO band. IR spectroscopic data for PdAg2/α-Al2O3 suggest that Pd in this sample occurs as isolated atoms on the surface of bimetallic nanoparticles, as is indicated by the almost complete absence of bridged adsorbed CO bands and by a significant weakening of the Pd–CO bond relative to the same bond in the bimetallic samples based on γ-Al2O3 and MgAl2O4 and in the monometallic reference sample Pd/γ-Al2O3.
      PubDate: 2016-11-01
      DOI: 10.1134/s0023158416060112
      Issue No: Vol. 57, No. 6 (2016)
       
  • The effects of thermal treatment of ZnO–ZnCr 2 O 4 catalyst on the
           particle size and product selectivity in dehydrocyclization of crude
           glycerol and ethylenediamine
    • Authors: Reema Sarkari; Vankudoth Krishna; Medak Sudhakar; Tumula Venkateshwar Rao; Aytam Hari Padmasri; Darbha Srinivas; Akula Venugopal
      Pages: 602 - 609
      Abstract: Abstract The ZnO–ZnCr2O4 (Zn–Cr–O) sample obtained by decomposition of Zn-Cr hydrotalcite precursor was subjected to the thermal treatment at different temperatures and the physico-chemical properties of the Zn–Cr–O system were compared with its catalytic behavior in dehydrocyclization of crude glycerol and ethylenediamine (EDA). Upon high temperature treatment of Zn–Cr–O the Cr6+ ions underwent autoreduction to form stable Cr3+ species and the particle size of both ZnO and ZnCr2O4 increased dramatically. Thermal effect did not influence the intermolecular cyclisation of EDA to form pyrazine. By contrast, an inversely proportional dependence was found between the rate of formation of 2-methylpyrazine and the particle size of Zn–Cr–O whereas the rate of 2-pyrazinylmethanol was directly proportional to the particle size.
      PubDate: 2016-09-01
      DOI: 10.1134/s0023158416050177
      Issue No: Vol. 57, No. 5 (2016)
       
  • Study of the oxygen exchange kinetics in the nonstoichiometric oxide SrFeO
           3–δ under isostoichiometric conditions using the oxygen partial
           pressure relaxation technique
    • Authors: S. F. Bychkov; M. P. Popov; A. P. Nemudry
      Pages: 697 - 703
      Abstract: Abstract The kinetics of oxygen exchange in the nonstoichiometric strontium ferrite SrFeO3–δ with the structure of cubic perovskite was studied by the oxygen partial pressure relaxation technique in the isostoichiometric regime at temperatures of 500–900°C in a range of δ from 0.24 to 0.44. An increase in the oxygen nonstoichiometry δ was accompanied by a decrease in the rate of sample relaxation and by an increase in the apparent activation energy of oxygen exchange.
      PubDate: 2016-09-01
      DOI: 10.1134/s0023158416050050
      Issue No: Vol. 57, No. 5 (2016)
       
 
 
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