Factors determining selectivity of ethylene conversion to butadiene over aluminosilicate catalyst

A study has been made of the influence of temperature, partial pressure of C₂H₄, and contact time on the selectivity of direct conversion of ethylene to butadiene over an aluminosilicate catalyst. A critical analysis has been made of the competing directions of C₂H₄ conversion, which determine the selectivity of C₄H₆ formation under conditions of a heterogeneous-homogeneous mechanism in carrying out the process. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of the Ukraine, 31 Nauka Prospect, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 33, No. 2, pp. 78–82, March–April, 1997.     

Effect of the iron content on the properties of a zirconium dioxide catalyst in the hydrogenation of carbon monoxide

The hydrogenation of Co on zirconium dioxide catalysts containing from 0 to 10 mass % iron was studied. Small additions of iron up to about 0.5 mass % promote the ZrO₂ catalysts relative to the formation of C₂–C₄ olefins. In the presence of large iron additives, the catalyst operates as a complex metal-oxide system featuring interaction of its components. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, 252039 Kiev, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 33, No. 3, pp. 153–158, May–June, 1997.     

Effect of the nature of the support on the activity of palladium catalysts for oxidation of carbon monoxide

We have studied the catalytic activity of TiN_0.65, TiO₂, Al₂O₃, and palladium catalysts supported on them in the oxidation of carbon monoxide. The order in which the activities of the supported catalysts vary, Pd/Al₂O₃>Pd/TiO₂>Pd/TiN_0.65, is the reverse of the activity series for the supports. This is explained by the effect of transfer of electron density from the palladium to the substrate. Taras Shevchenko Kiev University, 64 Vladimirskaya ul., Kiev 252033, Ukraine, G. V. Kurdyumov Institute of the Physics of Metals, National Academy of Sciences of Ukraine, 36 Akademika Vernadskogo bul’var, Kiev-142 252642, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 34, No. 2, pp. 118–121, March–April, 1998.     

Kinetics and mechanism of the oxidation of arenes in the presence of heteropoly acids and palladium(II) complexes supported on silica gel

Pd(II) complexes and twelfth-series heteropoly acids (HPA) H₉[PMo₆V₆O₄₀] and H₃[PMo₁₂O₄₀] supported on silica gel oxidize benzene and toluene at 95°C. The formation of methyldiphenylmethane in the oxidation of toluene on HPA/SiO₂ and (PdCl₂−HPA)/SiO₂ catalysts, KIE>1 for the toluene/toluene-d₈ pair, and greater rate for toluene than for benzene are in accord with a one-electron transfer mechanism. L. M. Litvinenko Institute of Physical Organic and Coal Chemistry, National Academy of Sciences of Ukraine, 70 R. Lyuksemburg ul., Donetsk 340114, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 4, pp. 249–252, July–August, 1999.     

Electrochemical oxidation of sulfodifluoroacetic acid in the presence of halogens

The electrochemical oxidation of sulfodifluoroacetic acid (HOSO₂CF₂CO₂H) in the presence of Cl₂ or Br₂ gives halodifluoromethanesulfonic acid. The anodic oxidation of sulfodifluoromethanecarboxylate ion to form the sulfodifluoromethyl radical as an intermediate is proposed as the rate-determining step. Institute of Organic Chemistry, National Academy of Sciences of Ukraine, 5 Murmanskaya ul., Kiev 253094, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 4, pp. 246–248, July–August, 1999.     

Isothermal Reduction Behaviour of Some Metal Molybdates. Selective light alkane oxydehydrogenation and/or olefins partial oxidation

The reduction profile of several unpromoted and promoted metal molybdate catalysts was investigated correlating their reducibility with the reactivity in catalysis. Using the stoichiometric α- and β-nickel molybdate compounds it was observed that the reduction rate was significantly affected by the nature of the phase. The results show thatβ-NiMoO₄ phase led to a significant increase in the reduction rate with respect to α phase. The increased resistance to reduction by hydrogen due to the structure of the catalytic system is reported. It was found that there is a relationship between the reducibility of the catalysts and selectivity to dehydrogenation products, indicating that the lattice oxygen plays an important role in the reaction. The effect of MoO₃, TeO₂ and Te₂MoO₇ added to NiMoO₄ systems onthe reducibility of the catalyst and on the propylene oxidation were also studied. It wasobserved that the reduction rate was significantly affected by the nature of the doping element. The results show that NiMoO₄–MoO₃ combination led toa significant increase of the reduction resistance of the nickel molybdate while TeO₂ or Te₂MoO₇ addition increases its oxygen depletion rate.Ni–Mo–O systems (Mo/Ni>1) were found to favour low CO_x selectivity, high selectivity to C₃H₄O and C₃H₄O₂ and good propylene conversion. In presence of TeO₂ and Te₂MoO₇ doped Ni–Mo–O system both acrolein and propylene conversion were increased with respect to the undoped system. Ni–Mo–Te–O catalysts have been found to have a reducibility trend which fits well with the acrolein and acrylic acid formation from propylene oxidation in presence of molecular oxygen. This revised version was published online in July 2006 with corrections to the Cover Date.     

The effect of the modification conditions of natural mordenite on their catalytic characteristics in the selective reduction of NOx

The results of a search for optimum conditions for the modification of natural mordenites and the results of an investigation of their acidic characteristics by temperature programmed desorption of ammonia for the purpose of producing active and sulfur-resistant catalysts for the selective reduction of NO_x by lower hydrocarbons (C₁−C₄) are presented. It was shown that during the chemical modification of samples of mordenite-bearing rock, including acid treatment with 0.25–0.5 N sulfuric acid solutions, recationization, and subsequent decationization, the concentration of strong acid centers increases. Here the activity of the catalysts and the resistance to the effect of SO₂ in the selective reduction of NO_x to nitrogen by a propane-butane mixture are increased. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 2, pp. 125–129, March–April, 1999.     

Influence of the composition of Co-containing perovskites on their catalytic properties in the conversion of methane into higher hydrocarbons in non-stationary conditions

The oxidative coupling of methane in a periodic regime was studied using Co-containing perovskites as solid oxidants. Partial substitution of strontium with alkali metals in the perovskite SrCoO₃ increased the activity and selectivity of the catalyst with respect to higher hydrocarbons. The substituted catalysts continued to work after many oxidation-reduction cycles. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 36, No. 1, pp. 47–52, January–February, 2000.     

Kinetics, substrate selectivity and mechanisms of the first step in the oxidation of alkylbenzenes in the HVO3−H2SO4 system

The kinetics, kinetic isotope effects, and substrate selectivity were studied for the oxidation of alkylbenzenes in the HVO₃−H₂SO₄ system at 30°C. The reaction proceeds by an electrophilic substitution mechanism through a slow step involving formation of a charge transfer complex between the arene and VO ₂ ⁺ cation and is similar to nitration by the NO ₂ ⁺ cation. L. M. Litvinenko Institute of Physical Organic and Coal Chemistry, National Academy of Sciences of Ukraine, 70 R. Lyuksemburg ul., Donetsk 340114, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 6, pp. 349–353, November–December, 1999.     

Stereochemical features of the synthesis and the structure of fullerenes

Details of the design of decaplet fullerenes are discussed. A model of the cluster assembly of C₆₀, C₇₀, and C₈₀ monomers from mono-, bi-, and trihexacyclic compounds of carbon was developed on the basis of the described structural and stereochemical concepts. The autoadhesion in the supermolecular structure, the cluster macrorecombination of the π radicals, and the contribution from spin-polymerization effects to regulation of the organic synthesis of C_n fullerenes were examined. V. N. Bakul Institute of Superhard Materials, National Academy of Sciences of Ukraine, 2 Avtozavodskaya ul., Kiev 254074, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 3, pp. 145–149, May–June, 1999.     

Effect of mechanochemical treatment on the structure and physicochemical properties of MoO3

Using X-ray phase analysis, IR spectroscopy, and derivatography we have shown that when molybdenum(IV) undergoes mechanochemical treatment in a planetary mill, along with an increase in the specific surface area changes also occur in the chemical composition and structure. The Mo−O−Mo bonds of the oxide lattice and the terminal Mo=O bonds are weakened and lengthened, evidence for which comes from IR spectroscopy data. Partial reduction of the molybdenum ions occurs with formation of the phase MoO_2.8 in water, water-benzene, and water-alcohol medium. In the presence of ethanol, the Magnéli phase χ-Mo₈O₂₃ can be formed for a certain energy load according to a crystallographic shift mechanism. The presence of reduced phase and the increase in specific surface area promote an increase in the activity of the oxide in oxidation of benzene. Selective oxidation of benzene to maleic anhydride is favored by an increase in the relative content of the (020) crystallographic face. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 4, pp. 257–261, July–August, 1999.     

Liquid-phase noncatalytic butene oxidation with nitrous oxide

The kinetics and mechanism of noncatalytic liquid-phase oxidation of but-1-ene and but-2-ene with nitrous oxide in a benzene solution in the temperature range from 180 to 240°C were studied. Oxidation proceeds via the 1,3-dipolar cycloaddition mechanism to form carbonyl compounds. Both of these reactions occur with close rates and activation energies and have the first orders with respect to the alkene and N₂O. A considerable fraction (39%) of but-1-ene involved in oxidation undergoes cleavage at the double bond yielding propanal and an equivalent amount of methylene, the latter producing ethylcyclopropane and cycloheptatriene. The oxidation of but-2-ene proceeds with a minimum bond cleavage and affords methyl ethyl ketone with 84% selectivity. Regularities of the oxidation of terminal and internal alkenes C₂—C₈ with nitrous oxide were analyzed using the previously published data. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 925–933, April, 2005.     

Influence of alkaline earth metals on the activity and sulfur stability of zeolites in the Nox−C3−C4 hydrocarbon selective reduction of no to nitrogen (SKV) process

The results of the influence of alkaline earth metal and magnesium cations on the activity and sulfur stability of catalysts based on synthetic mordenites and high-silicon zeolites with pentasil structures on the selective reduction of nitrogen oxides with C₃−C₄ hydrocarbons are presented. Doping the H-form of mordenite and pentasils with Ca, Sr, Ba, and Mg cations increased their activity and stability with respect to sulfur dioxide in the selective reduction of NO_x with a propane-butane mixture. L. V. Pisarzhevskii Institute of Physical Chemistry, Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 5, 317–321, September–October, 1999.     

Catalytic properties of the carbides of transition metals in oxidation reactions

It was shown that the carbides of transition metals are effective catalysts of oxidation reactions on account of their metal-like nature, combined with their high chemical and thermal stability. The results from systematic investigations into the catalytic characteristics of the carbides in the oxidation of hydrogen, carbon monoxide, and ammonia and in the oxidative coupling of methane (OCM) are examined. The first two reactions are total oxidation processes, and the oxidation of ammonia is a selective oxidation process. The oxidative coupling of methane is a heterogeneous-homogeneous process and represents a prospective method for the direct transformation of methane into higher hydrocarbons. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 34, No. 5, pp. 265–281, September–October, 1998.     

Platinum nanoparticle size effect on specific catalytic activity in <Emphasis Type="Italic">n</Emphasis>-alkane deep oxidation: Dependence on the chain length of the paraffin

The specific activity of 0.8% Pt/Al₂O₃ catalysts in the deep oxidation of C₁–C₆ n-alkanes increases with an increase in the Pt particle size from 1 to 3–4 nm. Further coarsening of the particles insignificantly changes the specific activity. The size effect was studied for a series of catalysts containing platinum nanoparticles 1 to 11 nm in diameter. The specific catalytic activity variation range depends on the size of the reacting hydrocarbon molecules. As the platinum particle size increases, the specific catalytic activity increases 3–4 times for the oxidation of CH₄ and C₂H₆ and by a factor of 20–30 for the oxidation of n-C₄H₁₀ and n-C₆H₁₄.     

Dehydrocondensation of methane to higher hydrocarbons on bifunctional catalysts in the absence of oxidizing agents in the gas phase

A study was carried out on the effect of the chemical nature of M_xL_y on the activity and selectivity of bifunctional M_xL_y/zeolite catalysts, where M_xL_y are metal-like transition metal compounds, M is a metal atom (Co, Mo, or W), and L is a nonmetal atom (B or Si), in the dehydrocondensation of methane to give higher hydrocarbons in the absence of gas-phase oxidizing agents. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, 252039 Kiev, Ukraine. Translated from éksperimental’naya i Teoreticheskaya Khimiya, Vol. 33, pp. 243–247, July–August, 1997.     

Separation of C1–C4 hydrocarbon gases on impregnated liquid membranes

Diffusion plays an important role along with complexation in the separation of C₁–C₄ hydrocarbon gases on copper-containing impregnated liquid membranes. The partition factor changes as the process goes from nonsteady-state to steady-state. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 34, No. 3, pp. 191–195, May–June, 1998.     

Principal relationships of the heterogeneous catalytic oxidation of benzene and its derivatives

The results of investigations into the processes involved in the heterogeneous catalytic oxidation of benzene and its derivatives at the L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, are summarized. The mechanisms of the full and partial oxidation of benzene, toluene, and their halogen derivatives are discussed. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, Kiev. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 34, No. 3, pp. 133–147, May–June, 1998.     

Spectral characteristics and redox behavior of the polynuclear managanese(III,IV) complex [Mn12O12(CH3COO)16(H2O)4] in liquid-phase oxidation of benzene

We have shown that benzene is oxidized to phenol by the polynuclear manganese complex [Mn₁₂O₁₂(CH₃COO)₁₆(H₂O)₄] in acetonitrile solution at room temperature and atmospheric pressure, with better than 80% selectivity. We have established that introduction of oxygen from the air into the reaction mixture as the reoxidant does not make it a catalytic process. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 252039, Ukraine. Translated fromTeoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 2, pp. 99–102, March–April, 1999.     

Effect of the extent of oxidation of activated carbons by O2 and HNO3 on the acidity and composition of surface functional groups and their ion-exchange properties

We have studied the effect of the extent of oxidation of carbon sorbents KAU and SKN by different oxidizing agents on the acidity of the surface functional groups and their qualitative composition, and also the selectivity of sorption of copper and lead ions from drinking water under static and dynamic conditions. We propose a mechanism for the formation of different types of acid groups on the carbon surface during its progressive oxidation. Institute for Sorption and Problems of Endoecology, National Academy of Sciences of Ukraine, 32/34 Akademika Palladina Prosp., Kiev-142, Ukraine 252680. Loughborough University, Loughborough, Great Britain. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 34, No. 1, pp. 27–31, January–February, 1998.