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CHEMISTRY (598 journals)

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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  [2355 journals]
  • Kinetics and mechanism of the photolysis of CF 2 ClBr exposed to light
           with a wavelength of 253.7 nm
    • Authors: T. I. Belyakova; I. K. Larin; N. A. Messineva; A. I. Spasskii; E. M. Trofimova
      Pages: 105 - 110
      Abstract: CF2ClBr mixed with oxygen was photolyzed using a low pressure mercury lamp, and the kinetics of photolysis was studied. The absorption spectra of the starting material and products of photolysis were recorded in the wavelength range from 200 to 900 nm on an Agilent 8453 spectrophotometer. The concentrations of the main photolysis products at different irradiation times were calculated by the mathematical processing of the absorption spectra. The scheme of CF2ClBr photolysis was suggested, the model calculations according to this scheme were performed, and the results of simulation were compared with experimental data.
      PubDate: 2017-03-01
      DOI: 10.1134/s002315841702001x
      Issue No: Vol. 58, No. 2 (2017)
       
  • Kinetic scheme and rate constants for methyl methacrylate synthesis
           occurring via the radical–coordination mechanism
    • Authors: N. V. Ulitin; K. A. Tereshchenko; A. K. Frizen; A. O. Burakova; S. V. Kolesov; D. A. Shiyan; N. E. Temnikova
      Pages: 122 - 132
      Abstract: Two kinetic schemes of the bulk radical–coordination polymerization of methyl methacrylate initiated by the benzoyl peroxide–ferrocene system are considered from the standpoint of formal kinetics. The most likely kinetic scheme is the one that includes the reactions characteristic of classical radical polymerization and, additionally, reactions of controlled radical polymerization proceeding via the Organometallic Mediated Radical Polymerization mechanism, a reaction generating a coordination active site, and a chain propagation reaction in the coordination sphere of the metal. The temperature dependences of the rate constants for the reactions of this kinetic scheme at temperatures typical of commercial poly(methyl methacrylate) production (313–353 K) have been determined by solving the inverse kinetic problem.
      PubDate: 2017-03-01
      DOI: 10.1134/s0023158417020136
      Issue No: Vol. 58, No. 2 (2017)
       
  • Catalytic and inhibiting effects of ferrocene on the bulk
           radical–coordination polymerization of methyl methacrylate from the
           standpoint of formal kinetics
    • Authors: K. A. Tereshchenko; N. V. Ulitin; S. V. Kolesov; A. O. Burakova; D. A. Shiyan; N. E. Temnikova
      Pages: 133 - 139
      Abstract: The kinetic curves and rates of bulk radical–coordination polymerization of methyl methacrylate initiated by the benzoyl peroxide–ferrocene system at 293–373 K, initial benzoyl peroxide concentrations of 10–4–10–1 mol/L, and a constant initial ferrocene concentration of 10–3 mol/L have been calculated using a mathematical model in which the process is considered from the standpoint of formal kinetics. The calculations have demonstrated that, at low methyl methacrylate conversions, ferrocene catalyzes the process at any benzoyl peroxide concentration; at medium and high methyl methacrylate conversions, deficient amounts of ferrocene with respect to benzoyl catalyze the process as well, while excess ferrocene inhibits the process. The observed effect is explained by the specific ferrocene–benzoyl peroxide interaction, which, depending on the ferrocene: benzoyl peroxide ratio, either increases or decreases the concentration of radicals in the reaction mass.
      PubDate: 2017-03-01
      DOI: 10.1134/s0023158417020124
      Issue No: Vol. 58, No. 2 (2017)
       
  • Oxidative dehydrogenation of ethane over a Mo–V–Nb–Te–O
           mixed-oxide catalyst in a cyclic mode
    • Authors: I. I. Mishanin; A. N. Kalenchuk; K. I. Maslakov; V. V. Lunin; A. E. Koklin; E. D. Finashina; V. I. Bogdan
      Pages: 156 - 160
      Abstract: The oxidative dehydrogenation of ethane (ODE) into ethylene over a Mo–V–Nb–Te–O mixedoxide catalyst in a cyclic mode with alternate feeding of ethane and air has been investigated. The amount of oxide-phase oxygen involved in the reaction has been estimated by titrating the oxygen of the active phase of the catalyst with ethane. The reactivity of this oxygen increases with an increasing temperature. The amount active oxygen involved in ODE at 360–400°C is 0.2–0.6 mmol/g.
      PubDate: 2017-03-01
      DOI: 10.1134/s0023158417020094
      Issue No: Vol. 58, No. 2 (2017)
       
  • Thermal deactivation mechanism and the effect of Nd addition on the
           deactivation of the Pt/SiO 2 catalyst for NO oxidation reaction
    • Authors: Y.-K. Chung; H.-I. Lee
      Pages: 161 - 166
      Abstract: Pt-based catalysts cannot be used permanently for the diesel after-treatment system because the catalytic activity is decreased due to coarsening of Pt particles at high temperature of the exhaust gas. In this study, to prevent Pt-based catalyst from deactivation, Nd was added to the Pt/SiO2 catalyst, and the effect of the Nd addition on the catalytic activity was investigated. The Pt/SiO2 catalyst showed a high catalytic activity for the oxidation of NO but was severely deactivated after the fast thermal aging process. Pt crystallite size was increased and some Pt particles were buried in the SiO2 pore during the fast thermal aging process, which led to the decrease of catalytic activity. Nd-added Pt/SiO2 catalyst showed lower activity than Pt/SiO2 catalyst, but Pt–Nd/SiO2 catalyst maintained its catalytic activity after fast thermal aging process. It can be postulated that a stable Nd silicate, on which Pt particle is placed, protects SiO2 pores from destruction and so the number of the catalytically active sites remains nearly unchanged. As a result the Pt–Nd/SiO2 catalyst maintained its catalytic activity after fast thermal aging process.
      PubDate: 2017-03-01
      DOI: 10.1134/s0023158417020045
      Issue No: Vol. 58, No. 2 (2017)
       
  • Preparation and characterization of microcapsulated red phosphorus and
           kinetic analysis of its thermal oxidation
    • Authors: Jie Liu; Hua Guan; Dongming Song
      Pages: 191 - 197
      Abstract: Microcapsulated red phosphorus (MRP) with aluminum hydroxide/phenolic resin coating layer was prepared by a two-step coating process. The results of Fourier-transform infrared spectroscopy and scanning electron microscopy show that red phosphorus (RP) is coated by aluminum hydroxide and phenolic resin. MRP absorbs less water and is more thermally stable than RP. The thermal oxidation kinetics of MRP was investigated by TG/DTG/DTA under air atmosphere using non-isothermal experiments with the heating rates ranging from 10 to 25°C/min. The values of the apparent activation energy E a were 168 ± 9 kJ/mol as determined by the isoconversional Ozawa–Flynn–Wall method and 164 ± 12 kJ/mol according to the Kissinger−Akahira−Sunose method. Based on Málek’s procedure the kinetic reaction follows the Šesták–Berggren model with f(α) = α0.34(1 − α)0.94 (α is RP conversion) and pre-exponential factor A = 3.11 × 1012 s–1. The simulated curves were fitted with experimental curves constructed by plotting dα/dt vs temperature at different heating rates.
      PubDate: 2017-03-01
      DOI: 10.1134/s0023158417020070
      Issue No: Vol. 58, No. 2 (2017)
       
  • Mathematical modeling of heterogeneous catalysis involving
           polymer-supported catalysts
    • Authors: H. A. Silva; L. G. Aguiar
      Pages: 211 - 217
      Abstract: This study reports the mathematical modeling of catalytic reaction systems involving polymer-supported catalysts. Differential mass balances were applied to species and the partial differential equations were solved through the method of lines in MATLAB®. Etherification and esterification reactions were studied with the present model and validation was performed with literature data, providing fair agreement. Furthermore, the model proved capable of predicting concentration gradients along the catalyst particles, providing an interesting level of detail to represent catalytic heterogeneous systems.
      PubDate: 2017-03-01
      DOI: 10.1134/s0023158417020112
      Issue No: Vol. 58, No. 2 (2017)
       
  • Role of hydrogen enrichment on acetylene emission during benzene oxidation
    • Abstract: A zero-dimensional model (perfectly-stirred reactor) in conjunction with CHEMKIN II and a scheme resulting from the merging of validated kinetic schemes for the oxidation of benzene were used to investigate the effect of hydrogen addition on the formation-depletion of C2H2, which is known as a soot precursor. The current modeling study treats the dependence of acetylene amounts on hydrogen percentage in the fuel mixture, and defines the key reaction mechanisms responsible for the observed reduction in C2H2 and consequently in polycyclic aromatic hydrocarbons and soot amounts induced by the hydrogen additive. The main objective of this work was to obtain fundamental understanding of the mechanisms, through which the hydrogen affects the acetylene yields. It was found that, at high temperatures hydrogen/benzene fuel mixtures displayed lower acetylene concentrations compared to the pure benzene fuel, whereas opposite trends were observed at low reaction temperatures.
      PubDate: 2017-05-01
       
  • One-pot solvothermal synthesis of hypercrosslinked porous ionic polymer
           and its catalytic activity
    • Abstract: The hypercrosslinked porous ionic polymer has been synthesized via one-pot polymerization and quaternization of vinyl pyridine and chloromethyl styrene under solvothermal condition. The effects of solvents and synthetic process on the polymer structure were investigated. Polymer from n-butanol showed the highest BET surface area of 555.6 m2/g. The catalytic activities were investigated though the aza-Michael addition and the results showed that the polymer owned even higher activity than homogenous ionic liquid. The high BET surface area, high catalytic activity and high stability made the polymer hold great potential for green chemical processes.
      PubDate: 2017-05-01
       
  • Reactivity of haloalkanes in their reactions with the chlorine atom
    • Abstract: Experimental kinetic data on reactions of the chlorine atom with halogenated derivatives of methane and ethane (37 reactions) have been analyzed by the intersecting-parabolas method. The following five factors have an effect on the activation energy of these reactions: the enthalpy of reaction, triplet repulsion, the electronegativities of the reaction center atoms, the dipole–dipole and multidipole interactions between the reaction center and polar groups, and the effect of π electrons in the vicinity of the reaction center. The increments characterizing the contribution from each factor to the activation energy of the reaction have been calculated. The contribution from the polar interaction, ΔE μ, to the activation energy depends on the dipole moment of the polar group and obeys the following empirical equation: ln(ΔE μ/Σμ) = −0.74 + 0.87(ΔE μ/Σμ) − 0.084(ΔE μ/Σμ)2.
      PubDate: 2017-05-01
       
  • Saturation kinetics and relative reactivity of the double bonds of
           alicyclic dienes in their hydrogenation
    • Abstract: The kinetics of the liquid-phase hydrogenation of cyclodienes with various structures (endo-tricyclo[ 5.2.1.02,6]decadiene-3,8 and cis,cis-1,5-cyclooctadiene) by hydrogen over a finely dispersed 1%Pd/C catalyst at atmospheric pressure has been studied. The catalyst provides the possibility for successive saturation of the double bonds of the dienes. The reactivities of the cyclodienes determined by their electron-donating properties have been compared. The solvent nature is the determining factor in the ratio of hydrogen absorption rates in the case of successive saturation of the double bonds of the hydrocarbons. The hydrogenation kinetics of cyclic dienes, including dicyclopentadiene, can be modeled using the Langmuir–Hinshelwood equation when the process is carried out in a perfectly mixed flow reactor.
      PubDate: 2017-05-01
       
  • Ignition induced the short-term action of UV light as possible evidence of
           chain branching in the reacting CH 3 Cl + Cl 2 mixture
    • Abstract: Ignition takes place in a mixture of chloromethane and chlorine at atmospheric pressure and room temperature 0.1 s after the irradiation of the mixture with a UV light pulse from a mercury quartz lamp. Temperature fields are presented, which demonstrate the development of the ignition process in the dark period. Calculations show that, after the initiation is stopped, the concentration of chlorine atoms decreases to a critical value within a time of the order of 0.02 s. The observed ignition can be explained by chains branching caused by the decay of the excited CCl 3 * radical that have accumulated energy upon the successive substitution of chlorine atoms for hydrogen in the chloromethane molecule.
      PubDate: 2017-05-01
       
  • Performance of a zeolite-containing catalyst and catalysts based on noble
           metals in intermolecular hydrogen transfer between С 6 hydrocarbons
    • Abstract: The activities of a zeolite-containing catalyst and catalysts containing a noble metal in intermolecular hydrogen transfer between С6 hydrocarbons are compared. The zeolite-containing catalyst is ineffective in hydrogen transfer from cyclohexane to 1-hexene and in cyclohexene conversion at <400°С. Cyclohexene disproportionation at Т < 200°С takes place only over catalysts containing a noble metal. The cyclohexene conversion selectivity depends strongly on the support type. Using deuterated compounds, it has been demonstrated that intermolecular hydrogen transfer via the dehydrogenation–hydrogenation mechanism involves only the initial cyclohexene.
      PubDate: 2017-05-01
       
  • Catalytic activity of iron hydroxides and manganese hydroxides in the
           deoxygenation of water
    • Abstract: Catalysts prepared by the modification of FIBAN K-4 and FIBAN X-1 fibrous ion exchangers with the hydroxides of iron and manganese were developed and tested in a water deoxygenation process. It was established that the samples obtained by the supporting of Fe(III) hydroxide onto the FIBAN X-1 ampholyte were most effective. The conclusion that the high activity of the catalytic system is caused by the formation of a mixed phase of Fe(II) and Fe(III) hydroxides of the spinel type containing mobile (weakly bound) lattice oxygen was made. A reaction scheme was proposed to explain the reaction mechanism.
      PubDate: 2017-05-01
       
  • Computational fluid dynamics study of the dry reforming of methane over
           Ni/Al 2 O 3 catalyst in a membrane reactor. Coke deposition
    • Abstract: This work investigates the dry reforming of CH4 as an important process for the conversion of greenhouse gases to synthesis gas. The mixture of methane and CO2 is readily available in the greenhouse gas which makes realization of dry reforming of methane process more convenient. The paper is an attempt to numerically analyse by computational fluid dynamics (CFD) the coking and gasification mechanisms in the lab-scale membrane module with a fixed-bed supported nickel catalyst (Ni/Al2O3). The concentrations and molar fluxes obtained by the simulation are compared with the experimental profiles to validate the CFD model. It was found that working in a catalytic fixed-bed membrane reactor, in the case of the dry reforming of methane and under specific conditions, was not critical, from the point of view of catalyst deactivation.
      PubDate: 2017-05-01
       
  • UV laser synthesis of nanoparticles in the gas phase
    • Abstract: This review deals with the UV laser photodissociation of metal carbonyls, ferrocene, carbon suboxide, and other precursors. The formation of supersaturated atomic vapors followed by the formation of carbon, metal, and metal–carbon nanoparticles is discussed. Application of UV laser synthesis to preparation of catalytic nanomaterials is considered.
      PubDate: 2017-05-01
       
  • CO oxidation by oxygen of the catalyst and by gas-phase oxygen over
           (0.5–15)%CoO/ZrO 2
    • Abstract: CO adsorption on (0.5–15)%CoO/ZrО2 catalysts has been investigated by temperature-programmed desorption and IR spectroscopy. At 20°С, carbon monoxide forms carbonyl and monodentate carbonate complexes on Co m 2+ O n 2- clusters located on the surface of crystallites of tetragonal ZrO2. With an increasing CoO content of the clusters, the amount of these complexes increases and the temperature of carbonate decomposition, accompanied by CO2 desorption, decreases from 400 to 304°С. On the 5%CoO/ZrО2 sample, the carbonyls formed on the Со2+ and Со+ cations and Со0 atoms decompose at 20, 90, and 200–220°С, respectively, releasing CO. At 20°С, they are oxidized by oxygen to monodentate carbonates, which decompose at 180°С. Adsorbed oxygen decreases the temperature of their decomposition on oxidation sites by ~40°C, and the sample remains in an oxidized state ensuring the possibility of subsequent CO adsorption and oxidation. The rate of the oxidation of 5%CoO/ZrО2 containing adsorbed CO by oxygen is higher than the rate of the oxidation of the same sample reduced by carbon monoxide, because the latter reaction is an activated one. In view of the properties of the complexes, it can be concluded that the carbonates decomposing at 180°С are involved in CO oxidation by oxygen from the gas phase in the presence of hydrogen, a process occurring at 50–200°С. The rate-limiting step of this process the decomposition of the carbonates, which is characterized by an activation energy of 77–94 kJ/mol.
      PubDate: 2017-05-01
       
  • Kinetics of n -hexane isomerization over supported palladium catalysts
    • Abstract: The steady- and unsteady-state kinetics of n-hexane isomerization over Ni- or Co-promoted Pd/HZSM-5 catalysts in the presence of hydrogen has been investigated. The kinetics of the reaction is described by similar fractional rational rate equations differing in the values of their constants. Hydrogen exerts a favorable effect on the isomerization rate. The catalysts have been characterized by the BET-N2 method, X-ray diffraction, transmission electron microscopy, H2-TPR, and NH3-TPD. The introduction of a promoter (Ni or Со) strengthens the adsorption of the reactants and increases the amount of reactants adsorbed.
      PubDate: 2017-05-01
       
  • Dioxovanadium(V) complexes of Schiff and tetrahydro-Schiff bases
           encapsulated in zeolite-Y for the aerobic oxidation of styrene
    • Abstract: A series of dioxovanadium(V) complexes of Schiff and tetrahydro-Schiff bases were encapsulated into the supercages of zeolite-Y and were characterized by X-ray diffraction, SEM, N2 adsorption/desorption, FT-IR, UV-vis spectroscopy, ICPAES, pair distribution function (PDF) and X-ray absorption near edge structure (XANES) measurements. The encapsulation is achieved by a flexible ligand method in which the transition metal cations were first ion-exchanged into zeolite-Y and then complexed with ligands. The dioxovanadium-exchanged zeolite, dioxovanadium complexes encapsulated in zeolite-Y plus non-encapsulated homogeneous counterparts were all screened as catalysts for the aerobic oxidation of styrene under mild conditions. It was found that the encapsulated complexes showed better activity than their respective nonencapsulated counterparts in most cases. All encapsulated dioxovanadium tetrahydro-Schiff base complexes showed much higher activity in aerobic oxidation of styrene than their corresponding Schiff base complexes.
      PubDate: 2017-05-01
       
  • Kinetics of the catalytic reforming of gasoline
    • Abstract: The main routes of catalytic gasoline reforming are considered. A kinetic model is chosen, substantiated, and modified to adequately describe the most important chemical reactions occurring in the process. The kinetic model is used to construct a mathematical model taking into account the nonisothermal character of the process. To reconcile calculated data with the corresponding industrial data, kinetic parameters (activation energies of reactions and preexponential factors of the Arrhenius equation) have been corrected for basic reactions of the process and have been redetermined for some ones. Process stages and concentration profiles of groups of reactants have been analyzed. Foundations have been laid for modeling of the entire chemical technological system of the catalytic reforming process.
      PubDate: 2017-05-01
       
 
 
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