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  Subjects -> CHEMISTRY (Total: 837 journals)
    - ANALYTICAL CHEMISTRY (48 journals)
    - CHEMISTRY (586 journals)
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CHEMISTRY (586 journals)            First | 1 2 3 4 5 6 | Last

Journal of Catalysts     Open Access  
Journal of Chemical & Engineering Data     Full-text available via subscription   (Followers: 11)
Journal of Chemical and Biological Interfaces     Full-text available via subscription  
Journal of Chemical Education     Full-text available via subscription   (Followers: 16)
Journal of Chemical Health Risks     Open Access   (Followers: 2)
Journal of Chemical Information and Modeling     Full-text available via subscription   (Followers: 6)
Journal of Chemical Research     Full-text available via subscription   (Followers: 5)
Journal of Chemical Science and Technology     Open Access   (Followers: 3)
Journal of Chemical Sciences     Partially Free   (Followers: 16)
Journal of Chemical Theory and Computation     Full-text available via subscription   (Followers: 12)
Journal of Cheminformatics     Open Access   (Followers: 1)
Journal of Chemistry     Open Access   (Followers: 3)
Journal of Chemometrics     Hybrid Journal   (Followers: 10)
Journal of Chromatography A     Hybrid Journal   (Followers: 53)
Journal of Chromatography Library     Full-text available via subscription   (Followers: 5)
Journal of Clinical Toxicology     Open Access   (Followers: 1)
Journal of Colloid and Interface Science     Hybrid Journal   (Followers: 13)
Journal of Computational Chemistry     Hybrid Journal   (Followers: 15)
Journal of Coordination Chemistry     Hybrid Journal   (Followers: 1)
Journal of Dispersion Science and Technology     Hybrid Journal  
Journal of Encapsulation and Adsorption Sciences     Open Access   (Followers: 4)
Journal of Environmental Chemistry and Ecotoxicology     Open Access   (Followers: 2)
Journal of Flow Chemistry     Full-text available via subscription   (Followers: 1)
Journal of Fluorescence     Hybrid Journal   (Followers: 4)
Journal of Fluorine Chemistry     Hybrid Journal   (Followers: 6)
Journal of Fuel Chemistry and Technology     Full-text available via subscription   (Followers: 5)
Journal of Great Lakes Research     Hybrid Journal   (Followers: 7)
Journal of Heterocyclic Chemistry     Hybrid Journal   (Followers: 5)
Journal of Immunoassay and Immunochemistry     Hybrid Journal   (Followers: 3)
Journal of Inclusion Phenomena and Macrocyclic Chemistry     Hybrid Journal   (Followers: 1)
Journal of Inorganic Biochemistry     Hybrid Journal   (Followers: 2)
Journal of Labelled Compounds and Radiopharmaceuticals     Hybrid Journal   (Followers: 1)
Journal of Macromolecular Science, Part A: Pure and Applied Chemistry     Hybrid Journal   (Followers: 3)
Journal of Mass Spectrometry     Hybrid Journal   (Followers: 24)
Journal of Materials Chemistry A : Materials for Energy and Sustainability     Full-text available via subscription   (Followers: 22)
Journal of Materials Chemistry B : Materials for Biology and Medicine     Full-text available via subscription   (Followers: 5)
Journal of Materials Chemistry C : Materials for Optical, Magnetic and Electronic Devices     Full-text available via subscription   (Followers: 5)
Journal of Materials Physics and Chemistry     Open Access  
Journal of Materials Research     Full-text available via subscription   (Followers: 10)
Journal of Mathematical Chemistry     Hybrid Journal   (Followers: 5)
Journal of Medicinal Chemistry     Full-text available via subscription   (Followers: 75)
Journal of Membrane and Separation Technology     Hybrid Journal  
Journal of Membrane Science     Hybrid Journal   (Followers: 11)
Journal of Modern Chemistry & Chemical Technology     Full-text available via subscription   (Followers: 2)
Journal of Molecular Catalysis A: Chemical     Hybrid Journal   (Followers: 3)
Journal of Molecular Graphics and Modelling     Hybrid Journal   (Followers: 4)
Journal of Molecular Liquids     Hybrid Journal   (Followers: 1)
Journal of Molecular Modeling     Hybrid Journal   (Followers: 3)
Journal of Molecular Recognition     Hybrid Journal   (Followers: 2)
Journal of Molecular Spectroscopy     Hybrid Journal   (Followers: 7)
Journal of Molecular Structure     Hybrid Journal   (Followers: 3)
Journal of Nanoparticles     Open Access  
Journal of Nanostructure in Chemistry     Open Access   (Followers: 3)
Journal of Natural Gas Chemistry     Full-text available via subscription   (Followers: 2)
Journal of Nepal Chemical Society     Open Access  
Journal of Nucleic Acids Investigation     Open Access   (Followers: 2)
Journal of Ocean University of China (English Edition)     Hybrid Journal   (Followers: 1)
Journal of Organometallic Chemistry     Hybrid Journal   (Followers: 13)
Journal of Photochemistry and Photobiology A: Chemistry     Hybrid Journal   (Followers: 4)
Journal of Photochemistry and Photobiology C: Photochemistry Reviews     Full-text available via subscription   (Followers: 3)
Journal of Polymer & Composites     Full-text available via subscription   (Followers: 3)
Journal of Polymer and Biopolymer Physics Chemistry     Open Access   (Followers: 2)
Journal of Polymer Science Part A: Polymer Chemistry     Hybrid Journal   (Followers: 117)
Journal of Polymers     Open Access   (Followers: 1)
Journal of Porphyrins and Phthalocyanines     Hybrid Journal   (Followers: 2)
Journal of Pure and Applied Chemistry Research     Open Access   (Followers: 1)
Journal of Raman Spectroscopy     Hybrid Journal   (Followers: 11)
Journal of Research Updates in Polymer Science     Hybrid Journal  
Journal of Saudi Chemical Society     Open Access  
Journal of Solid State Chemistry     Hybrid Journal   (Followers: 14)
Journal of Solution Chemistry     Hybrid Journal   (Followers: 4)
Journal of Structural Chemistry     Hybrid Journal  
Journal of Sulfur Chemistry     Hybrid Journal   (Followers: 2)
Journal of Superhard Materials     Hybrid Journal   (Followers: 1)
Journal of Surfactants and Detergents     Hybrid Journal   (Followers: 5)
Journal of Systems Chemistry     Open Access  
Journal of Taibah University for Science     Open Access  
Journal of the American Chemical Society     Full-text available via subscription   (Followers: 203)
Journal of the American Society for Mass Spectrometry     Hybrid Journal   (Followers: 21)
Journal of the American Society of Brewing Chemists     Full-text available via subscription   (Followers: 1)
Journal of the Bangladesh Chemical Society     Open Access  
Journal of the Chilean Chemical Society     Open Access   (Followers: 1)
Journal of the Iranian Chemical Society     Hybrid Journal  
Journal of the Korean Society for Applied Biological Chemistry     Hybrid Journal   (Followers: 1)
Journal of the Mexican Chemical Society     Open Access   (Followers: 1)
Journal of Theoretical and Computational Chemistry     Hybrid Journal   (Followers: 8)
Journal of Theoretical Chemistry     Open Access  
Journal of Wood Chemistry and Technology     Hybrid Journal   (Followers: 7)
JPC - Journal of Planar Chromatography - Modern TLC     Full-text available via subscription   (Followers: 5)
Jurnal Penelitian Sains (JPS)     Open Access  
Jurnal Teknologi Informasi     Open Access   (Followers: 3)
Karbala International Journal of Modern Science     Open Access  
Kinetics and Catalysis     Hybrid Journal   (Followers: 3)
Korea-Australia Rheology Journal     Hybrid Journal  
Langmuir     Full-text available via subscription   (Followers: 40)
Latvian Journal of Chemistry     Open Access   (Followers: 1)
Lebensmittelchemie     Hybrid Journal   (Followers: 1)
Lipid Insights     Open Access  
Luminescence     Hybrid Journal   (Followers: 1)
Macromolecular Materials & Engineering     Hybrid Journal   (Followers: 5)

  First | 1 2 3 4 5 6 | Last

Journal Cover   Kinetics and Catalysis
  [SJR: 0.367]   [H-I: 21]   [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  [2290 journals]
  • Highly efficient procedure for biodiesel synthesis using polypyrrole
           functionalized by sulfonic acid
    • Abstract: Abstract A novel polypyrrole functionalized by sulfonic acid was synthesized by the polymerization of N-butanesulfonic acid pyrrole using chemical oxidation. The catalytic activity of the solid acid was investigated in the transesterification of rapeseed oil. The results showed that the solid acid was very efficient in this reaction with a yield of 99%. Both the free fatty acids and triglycerides could be transformed to the methyl esters using the solid acid. Moreover, the water content in the raw material had little effect on the catalytic activity of the solid acid. The solid acid was characterized by operational simplicity, low cost, high acidity and good catalytic activity, indicating potentiality for using in “green” chemistry.
      PubDate: 2015-05-01
       
  • Calculating the rate constant for the NH 2 • + CO ⇄ NH 2 CO
           • ⇄ H + NHCO reactions and thermodynamic properties of NH 2 CO
           •
    • Abstract: Abstract The Δ f H 298 0 (NH2CO•) = −8.6 ± 1 kJ/mol and S 298 0 = 260.6 ± 5.2 J mol−1 K−1 values have been obtained using the energies of isodesmic reactions within the CBS-Q approximation. Use of the CBS-Q, UMP2, UBHandHLYP, and UB3LYP approaches has afforded the most substantiated entropy value, S 298 0 = 258.2 ± 2.8 J mol−1 K−1. The energetics of the NH2CO• ⇄ NH 2 • + CO and NH2CO• ⇄ H + NHCO reactions and their rate constants (k 1 and k 2, respectively) have been calculated using the UMP2, UBHandHLYP, and UB3LYP approaches. The rate constant values k 1, ∞ = 8.2 × 1010(T/298)1.18e−115/RT s−1, which were obtained within the UB3LYP approach, are in closest agreement with available experimental data. The constants k 2, ∞ = 4.0 × 107(T/298)1.7e−149/RT s−1, obtained using the UMP2 approach, are best consistent with indirect experimental evidence. The UB3LYP value of the rate constant of the NH 2 • + CO reaction at P = 1 atm and T = 304 K (k −1 = 2.2 × 10−18 cm3 molecule−1 s−1) suggests that this reaction should make a significant contribution to the removal of NH 2 • from the atmosphere under pre-abiogenesis conditions. The resulting NH2CO• adduct is a fairly stable compound capable of participating in the formation of the chemical composition of the prebiogenic atmosphere. This conclusion is supported by the small rate constant values k 1 = 3.3 × 10−7 s−1 and k 2 = 5.8 × × 10−18 s−1 at P = 1 atm and T = 304 K, which were calculated using the UB3LYP and UMP2 approaches. In addition, the k −2 = 2.8 × 10−21 cm3 molecule−1 s−1 value (P = 1 atm) for the NHCO + H reaction, calculated using the UMP2 approach, indicates that this reaction makes an insignificant contribution to the disappearance of H atoms and to the formation of NH2CO• under the abiogenesis conditions.
      PubDate: 2015-05-01
       
  • Kinetics of the reduction of orthorhombic and tetragonal lead oxides to
           lead with hydrogen
    • Abstract: Abstract The kinetics of the reduction of orthorhombic and tetragonal lead oxides to lead with hydrogen has been investigated in the temperature range from 450 to 525°C. The degree of reduction of lead in the orthorhombic oxide as a function of the reaction time is described by the Erofeev equation in which the exponent n is unity. No significant difference in reactivity toward hydrogen between orthorhombic and tetragonal lead oxides has been revealed. The activation energy of the lead oxide reduction reaction is 85.8 ± 8.3 kJ/mol for the orthorhombic phase and 93.1 ± 5.0 kJ/mol for the tetragonal phase, so these values are equal within the activation energy determination error.
      PubDate: 2015-05-01
       
  • Catalytic decomposition of light hydrocarbons over a Ni-Cu-Fe/Al 2 O 3
           catalyst for development of an associated petroleum gas utilization
           technology
    • Abstract: Abstract The decomposition of light hydrocarbons with use of a Ni-Cu-Fe/Al2O3 catalyst and the production of carbon nanomaterials and hydrogen as the main process products is proposed in this work for the utilization of associated petroleum gas in small and distant oil fields. It was found that a 70% Ni-10% Cu-10% Fe/Al2O3 catalyst is most effective in the decomposition of a propane-butane mixture in a temperature range of 700–725°C; under these conditions, to 700–750 L of H2 per gram catalyst can be obtained. The concentration of hydrogen at the reactor outlet was 70–75 mol %.
      PubDate: 2015-05-01
       
  • Mechanism of the reaction between N , N ′-diphenyl-1,4-benzoquinone
           diimine and thiophenol in n -propanol
    • Abstract: Abstract We studied the kinetics of the reaction between N,N′-diphenyl-1,4-benzoquinone diimine and thiophenol in n-propanol at 343 K and compared the results with the same data for the chlorobenzene medium. The replacement of chlorobenzene with n-propyl alcohol increases the reaction rate by one order of magnitude. The order of the reaction with respect to thiophenol was determined to be 1.0 in both solvents, and the order of the reaction with respect to quinone diimine decreases from 1.5 to 1.2 on passing from chlorobenzene to n-propanol. In contrast to the reaction in chlorobenzene, where the radical chain mechanism is realized, the reaction in n-propanol simultaneously proceeds via a radical chain channel and a heterolytic channel. In the absence of an initiator and at equal reactant concentrations of ∼10−4 mol/L, the reaction rates in both pathways are commensurable. The chain reaction is characterized by short chains whose length is a few units. Chain generation in the absence of an initiator occurs by the direct bimolecular reaction between the reactants, whose rate constant in n-propanol is one order of magnitude higher than that in chlorobenzene, which is explained by the high polarity of the transition state in this endothermic homolytic reaction. The reaction mechanism was proposed, and, for this mechanism, the rate constants of elementary steps were determined.
      PubDate: 2015-05-01
       
  • High-temperature ammonia oxidation over a platinum catalyst under
           conditions of the parallel formation of nitrogen-containing products
    • Abstract: Abstract Experimental data on the effect of the temperature of air containing low ammonia concentrations on the temperature and rate of catalytic ammonia combustion over a platinum catalyst as a function of the NH3 concentration and catalyst particle diameter are analyzed with account taken of thermal radiation under the assumption that nitrogen and nitric oxide form in parallel. At relatively low air temperatures (near the combustion extinction point), the ammonia combustion temperature is determined by the nitrogen formation reaction (which releases a larger amount of heat and is characterized by a lower activation energy). At higher air temperatures and ammonia concentrations, the combustion temperature is determined by the nitric oxide formation reaction (which releases a smaller amount of heat and is characterized by a higher activation energy). The dependence of the critical temperature of the gas mixture on the catalyst particle diameter under conditions of the catalytic autoignition of the combustible gas and combustion extinction (at low ammonia concentrations) has been determined and analyzed for the case in which there is radiative heat transfer between the gas and the cold walls of the reactor.
      PubDate: 2015-05-01
       
  • Kinetics and mechanism of photochromic transformations of a
           2,3-diarylcyclopentenone
    • Abstract: Abstract Photochemistry of recently synthesized 2,3-bis-(2,5-dimethylthiophen-3-yl-cyclopent-2-en-1-one) (diarylcyclopentenone, 1A) as a characteristic representative of photochromic 2,3-diarylcyclopent-2-en-1-ones (DCPs) was examined by means of stationary an nanosecond laser flash photolysis. Quantum yields of forward and backward photochemical reactions and molar absorption coefficient of the closed form were measured. Contradictions in the literature values of these parameters were eliminated. In laser flash photolysis experiments the formation of the 1A open form triplet state was exhibited, and the rate constants of the reactions of its decay were measured. 1A demonstrates rather low fatigue resistance, as any of other DCPs. In spite of the triplet state formation, photodegradation of 1A is not caused by the reactions of singlet oxygen.
      PubDate: 2015-05-01
       
  • The promoter action of CeO 2 for the Ni/Al 2 O 3 -catalyzed methanation of
           CO 2
    • Abstract: Abstract By adding 2 wt % CeO2 to the active metal (Ni) or to the Al2O3 support, the catalysts for CO2 methanation were prepared and the effect of the promoter on the catalytic performance was studied. For the sake of comparison, the 15 wt % Ni/Al2O3 catalyst was prepared via impregnation method. The CO2 methanation was carried out in a fixed-bed reactor under atmospheric pressure with a weight hourly space velocity (WHSV) 30000 mL/(g cat −1 h). It was found that addition of 2 wt % CeO2 either to the active metal or to the support of the 15 wt % Ni/Al2O3 catalyst both increased CO2 methanation performance. The catalysts were characterized by BET, XRD, H2-TPR, CO2-TPD, XPS and TEM techniques. When CeO2 was added to Ni the interaction of Ni with Al2O3 became stronger to decrease the Ni particle size and increase the degree of the Ni dispersion. As a result, the amounts of CO2 adsorbed on the active sites and the CO2 conversion considerably increased. When CeO2 was added into Al2O3 to form the composite supports, CO2 conversion was also increased but the effect was not as high as that observed when CeO2 was added to Ni.
      PubDate: 2015-05-01
       
  • Investigation of the mechanism of the inhibited oxidation of 1,4-dioxane
           by mathematical modeling
    • Abstract: Abstract The free-radical chain oxidation of 1,4-dioxane in the presence of an inhibitor has been investigated by mathematical modeling. The forward kinetic problem has been solved, and complete kinetic information about the reaction has been gained, including the variation of the concentrations of all reaction participants. The inverse kinetic problem has also been solved to determine the rate constants of all elementary steps.
      PubDate: 2015-05-01
       
  • Effect of the mechanical activation of a mixture of MnCO 3 · m Mn(OH)
           2 · n H 2 O and AlOOH as a stage of the preparation of a MnO x -Al 2
           O 3 catalyst on its phase composition and catalytic activity in CO
           oxidation
    • Abstract: Abstract The effect of the mechanical activation of a mixture of MnCO3 · mMn(OH)2 · nH2O and AlOOH as a stage in the preparation of a MnO x -Al2O3 catalyst on the characteristics of the resulting samples was studied. It was found that the catalytic activity of MnO x -Al2O3 increased even after mechanical activation for 5 min. It was established that a decrease in the concentration of manganese hydroxocarbonate within the limits of the tested ratios between the components exerted the greatest positive effect of mechanical activation on catalytic activity. This was likely because the dispersion of this compound increased and interactions between the components strengthened in the course of mechanical activation. This was evidenced by a considerable increase in the amount of the α-Al2O3 phase relative to δ-Al2O3 in the catalyst calcined at 950°C. According to the results of temperature-programmed reduction with hydrogen, the formation of a larger number of catalytically active, fine MnO x particles after high-temperature heat treatment was responsible for the strengthening of interactions between the initial components upon mechanical activation. Transmission electron-microscopic data also indicated an increase in the dispersity of manganese oxide particles with the use of mechanical activation as a stage of the preparation of the MnO x -Al2O3 catalyst.
      PubDate: 2015-05-01
       
  • Kinetic analysis of the hydroxyl mechanism of the antimalarial effect of
           fluorinated artemisinin derivatives
    • Abstract: Kinetic schemes of intramolecular oxidation are constructed for 13 derivatives of 10-dihydroartemisinin containing fluorine substituents (F and CF3). Each step of the kinetic scheme is characterized by its enthalpy. The activation energy and rate constant of each step are calculated using the intersecting parabolas model. The competition between mono- and bimolecular radical reactions is taken into account. In the case of H abstraction from the α-hydroperoxy-C-H bond, the fragmentation of the molecule with the formation of hydroxyl radicals concerted with the abstraction is taken into account. The antimalarial efficiency of each drug due to the hydroxyl radicals only is calculated from the empirical dependence of the antimalarial activity IC50 on the number of hydroxyl radicals n OH generated by the compound. The compounds whose antimalarial activity is additionally caused by other factors are revealed.
      PubDate: 2015-05-01
       
  • Methyl methacrylate polymerization involving a cobalt ortho
           -iminobenzosemiquinone complex: Determination of the chain transfer
           constant
    • Abstract: Abstract We studied the effect of bis[4,6-di-tert-butyl-N-(2,6-dimethylphenyl)-ortho-iminobenzosemi-quinono]cobalt(II) on the kinetics of the bulk polymerization of methyl methacrylate at 70°C and on the molecular-weight characteristics of the polymer synthesized. The effective chain transfer constant in the polymerization of methyl methacrylate in the presence of the complex in benzene at 70°C was determined by the Mayo method and by linearizing the macromolecule chain length distribution. The constants obtained were compared with the same parameters available from the literature for a number of known chain-transfer agents, viz., dodecyl mercaptan and cobalt porphyrin and oxime complexes.
      PubDate: 2015-05-01
       
  • Support pretreatment effect on the catalytic properties and reusability of
           silica-supported titania catalysts in 2,3,6-trimethylphenol oxidation with
           hydrogen peroxide
    • Abstract: Abstract The effects of some variants for silica support pretreatment on the catalytic properties and reusability of silica-supported titania in the liquid-phase oxidation of 2,3,6-trimethylphenol (TMP) into 2,3,5-trimethyl-1,4-benzoquinone (TMBQ) with hydrogen peroxide, a green oxidizer, have been investigated. The support pretreated with aqueous ammonia and then evacuated demonstrates the optimal activity, selectivity, and reusability of catalysts. The TMBQ selectivity reaches 93% at a TMP conversion of 90% in at least four cycles for the catalyst prepared.
      PubDate: 2015-05-01
       
  • Role of PdAg interface in Pd-Ag/SiO 2 bimetallic catalysts in
           low-temperature oxidation of carbon monoxide
    • Abstract: Abstract An approach to the development of bimetallic nanoparticles with the separated but interacting phases of silver and palladium was proposed to effectively separate the active sites of silver, which possess high activity in activation of molecular oxygen, and the sites of palladium-containing phases, which are responsible for CO adsorption. The structure of PdAg particles was determined using X-ray diffraction analysis, electronic diffuse reflectance spectroscopy, and temperature-programmed reduction. It was found that the introduction of silver led to easier reduction of palladium from oxidized states in an atmosphere of CO. The activity of the bimetallic PdAg catalysts in the oxidation of CO increased, as compared with that of the Pd/SiO2 catalyst. The oxidized bimetallic catalyst, in which palladium occurred in an oxide state, was even more effective in the oxidation of CO; this can be related to the better cooperation of the active sites of silver and palladium oxide, which are responsible for the activation and conversion of CO and oxygen at the Ag-PdO interfacial boundary.
      PubDate: 2015-05-01
       
  • Alkaline KMnO 4 oxidation of reducing sugars in microemulsions: Inhibition
           effect of surfactants
    • Abstract: Abstract The kinetics of oxidation of reducing sugars viz. D-glucose and D-fructose by alkaline KMnO4 in microemulsion media was investigated. The aqueous, cationic microemulsion was prepared from cetyl trimethyl ammonium bromide, n-butanol, n-hexane and water, whereas n-decane, aerosol-OT and water were used to prepare the anionic microemulsion. The order of reaction in oxidant was always found to be unity, while that in substrate and alkali was decreased from unity to zero at higher concentrations substrate and alkalirespectively. On decreasing [H2O]/[Surfactant] ratio (increasing surfactant content) in microemulsion, the observed rates constants of oxidation (k obs) were decreased. The inhibition effect on the rate of oxidation was greater in cationic microemulsion. A mechanism consistent with kinetic data is proposed.
      PubDate: 2015-05-01
       
  • Gas-phase oxidation of alcohols with dioxygen over an Au/TiO 2 catalyst:
           The role of reactive oxygen species
    • Abstract: Abstract The activity of the (3% Au)/TiO2 catalyst with an average gold particle size of 3.6 ± 1.0 nm in the gas-phase oxidation of lower aliphatic alcohols (ethanol, propanol, isopropanol, and butanol) into the corresponding carbonyl compounds (acetaldehyde, propanal, acetone, and butanal) has been studied. A two-peak profile of the activity of the catalyst as a function of temperature has been observed in all of the reactions. The first peak falls within the temperature range from 120 to 130°C, while the complete conversion of the alcohols is achieved at 200–300°C. It is hypothesized that the low-temperature activity is due to the generation of a thermally unstable reactive oxygen species on the catalyst surface.
      PubDate: 2015-05-01
       
  • Advantages of two-dimensional gas chromatography
    • Abstract: Abstract The potential of two-dimensional gas chromatography (GC × GC) for the investigation of complex mixtures of organic compounds is briefly reviewed. Various designs of modulators for GC × GC are considered. Requirements for the equipment necessary for the successful implementation of the GC × GC method are formulated. The main advantages of GC × GC over classical one-dimensional gas chromatography are listed. Typical separation problems that are solvable by GC × GC are considered.
      PubDate: 2015-05-01
       
  • Effect of support modification on the physicochemical properties of a
           NiPd/Al 2 O 3 catalyst for the autothermal reforming of methane
    • Abstract: Abstract For the development of effective catalysts for the autothermal reforming of methane, the NiPd catalysts were synthesized based on modified aluminum oxide and their physicochemical properties were studied using X-ray diffraction analysis, low-temperature nitrogen adsorption, transmission electron microscopy, and temperature-programmed reduction with hydrogen. It was found that the variation of modifying components (CeO2, ZrO2, La2O3, Ce0.5Zr0.5O2, and La2O3/Ce0.5Zr0.5O2) and their concentrations (10–30 wt %) makes it possible to regulate the particle size of NiO, the composition of a Ni-containing phase (NiO, La2NiO4, NiAl2O4, or Ni-La-Al-O) and the redox properties of nickel ions. It was shown that the average particle size of NiO increased from 6.7 to 17.5 nm in the following order of supports: La2O3/Al2O3 < La2O3/Ce0.5Zr0.5O2/Al2O3 < Al2O3 < Ce0.5Zr0.5O2/Al2O3 < CeO2/Al2O3 < ZrO2/Al2O3. On the introduction of the modifying oxides CeO2 and ZrO2 into aluminum oxide, the fraction of nickel in the composition of NiAl2O4 decreased and, therefore, the fraction of difficult-to-reduce Ni2+ decreased. The addition of La2O3 and La2O3/Ce0.5Zr0.5O2 strengthened the interaction of nickel cations with the support up to the formation of Ni-La-Al-O and La2NiO4 phases and increased the fraction of difficult-to-reduce Ni2+ ions. The resulting NiPd catalysts are promising in the catalysis of the autothermal reforming of methane.
      PubDate: 2015-05-01
       
  • Physicochemical properties and photocatalytic activity of H 3 PW 12 O 40
           /TiO 2
    • Abstract: Abstract For enhancing its photocatalytic activity, titanium dioxide P25 has been modified by adsorption of the heteropoly acid (HPA) H3PW12O40 from aqueous solution at an HPA concentration of 0.2 to 5 mmol/L. The deposition of the HPA does not alter the phase composition or morphology of the photocatalyst but only causes a slight change in its diffuse reflectance spectrum. IR spectroscopic and XPS studies have confirmed that the HPA molecules on the TiO2 surface are intact. The adsorption of the HPA increases the photovoltage and hydroxyl radical yield under UV irradiation. These characteristics reach their maximum values upon the adsorption of the HPA from its 0.5 mmol/L solution. Electrochemical measurements have demonstrated that the HPA increases the rate of interfacial electron transfer. The deposition of the HPA accelerates the gas-phase oxidation of acetaldehyde and the degradation of phenol and triethyl phosphate in the aqueous medium. The highest activity is shown by the catalyst obtained by the adsorption of H3PW12O40 from its 0.5 mM solution. The results of this study suggest that the HPA is promising for modifying the surface of the TiO2 photocatalyst.
      PubDate: 2015-05-01
       
  • Structural and textural characteristics of systems based on layered Mg-Al
           hydroxides
    • Abstract: Abstract Hydrotalcite-type layered Mg-Al hydroxides with Mg/Al ≥ 2 and related oxide systems have been synthesized and characterized. During the synthesis of the Mg-Al hydroxides with Mg/Al = 2 and 3, the interplanar spacings decrease because of the replacement of the interlayer NO 3 − anion by the CO 3 2− anion. Morphologically, the initial materials are aggregates of ∼1-μm oblong planar particles with a layered structure. The transverse dimension of the plates is 50–100 nm, and their thickness is 10–30 nm. As a rule, these planar particles are heavily distorted. Heat treatment of the Mg-Al hydroxides in the temperature range from 450 to 600°C causes the separation of the layered structures into planar domains of epitaxial MgAl2O4/MgO structures, which survive heat treatment at 900°C. During this heat treatment at 900°C, the greater part of the sample breaks down into two-dimensional particles of defective MgO and MgAl2O4 phases whose size is up to 100 nm. The oxide compositions synthesized from the layered Mg-Al hydroxides have a large pore volume and a fairly high specific surface area, which are retained upon heat treatment at 1000–1100°C.
      PubDate: 2015-05-01
       
 
 
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