Studies on catalytically active surface compounds, IX. Formation of O2? radicals on VCl4/SiO2 catalysts

The conditions for the formation of O ₂ ^– on VCl₄/SiO₂ catalysts have been investigated. It is shown that thermal vacuum treatment (TVT) of unhydrolyzed catalysts leads to partial hydrolysis of the surface vanadium complex caused by the silanol groups of the support. The ability of the catalysts to generate O ₂ ^– radicals was found to depend on the degree of hydrolysis caused by thermal vacuum treatment.

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O ₂ ^– VCl₄/SiO₂. , , . , O ₂ ^– , .

     

Kinetics of SO2 oxidation on K2S2O7?V2O5 catalyst in non-steady conditions

Studies of SO₂ oxidation on a molten component of vanadium catalysts in non-steadystate conditions indicates that the kinetics agree fairly well with an oxidation-reduction mechanism. In the low temperature range (<790 K) tetravalent vanadium can be partially crystallized.

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. , - . ( 790 ) .

     

Catalytic oxidative hydrolysis of H2PO2? anions in the presence of RhCl3

Kinetics of H₂ evolution in the RhCl₃–NaH₂PO₂–HCl–H₂O system has been studied. As found by³¹P NMR, Rh(I) complexes with the Rh–P(OH)₂O^– bond are formed and play the role of catalysts in the subsequent H₂ evolution reaction.

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H₂ RhCl₃–NaH₂PO₂–HCl–H₂O. ³¹P Rh(I) Rh–P(OH)₂O^–, H₂.

     

ESR studies of T3+ complexes formed in the catalytic system TiCl2(acac)1+Et2AlCl and their interaction with ethylene, carbon monoxide and pyridine

Coordination state of Ti³⁺ions formed in the homogeneous catalytic systems TiCl₂(acac)₂+Et₂AlCl, and its changes upon interaction with ethylene, carbon monoxide and pyridine have been studied by ESR.

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Ti³⁺, TiCl₂(acac)₂=Et₂AlCl, , .

     

Mechanism of ascorbic acid oxidation by molecular oxygen in aqueous pyridine catalyzed by CO2+, Ni2+, Mn2+ and Zn2+

Data on the radical non-chain mechanism of ascorbic acid oxidation by molecular oxygen catalyzed by Co²⁺, Ni²⁺, Mn²⁺ and Zn²⁺ ions are reported.

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Co²⁺, Ni²⁺, Mn²⁺ Zn²⁺.

     

Hydrocarbon synthesis from methanol on erionite and mordenite catalysts synthesized in the presence of B3+, Ga3+ or Fe3+

Selectivity of erionite and mordenite type aluminosilicates synthesized in the presence of B³⁺, Ga³⁺ or Fe³⁺ has been studied in methanol conversion to hydrocarbons. The olefin to paraffin ratio in the product is proportional to the Al₂O₃ content of the zeolites.

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, B³⁺, Ga³⁺ Fe³⁺. , / Al₂O₃ .

     

Catalytic oxidation of ascorbic acid by molecular oxygen in aqueous pyridine in the presence of Co2+, Ni2+, Mn2+ and Zn2+ ions

In aqueous pyridine solutions, Co²⁺, Ni²⁺, Mn²⁺ and Zn²⁺ effectively catalyze the oxidation of ascorbic acid by molecular oxygen. A kinetic expression consistent with the experimental data is given and a possible mechanism proposed.

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- , , . , . .

     

Chemiluminescence and auto-oscillations in the (S?Cr2O72+?UO22+) system

Quasi-harmonic oscillations of chemiluminescence intensity at certain concentrations of the components for the (S–Cr₂O ₇ ^2– –UO ₂ ²⁺ ) system in concentrated sulfuric acid and chemiluminescence and dark stages with the participation of intermediates Cr(V), U(IV) and sulfur peroxide radicals (HS₂O₆ ^.) have been discovered. Chemiluminescence is attributed to the interaction of HS₂O₆ ^. compounds. The processes of deactivation of the excited states of uranyl involve the participation of Cr(V). A scheme for the oscillation chemiluminescence reactions is suggested.

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(S–Cr₂O ₇ ^2– –UO ₂ ²⁺ ) H₂SO₄ , . Cr(V), U(IV) (HS₂O₆ ^.) HS₂O₆ ^. Cr(V) . .

     

Catalysts for metathesis of olefins, prepared by anchoring of MoO2(acac)2 to Al2O3

New highly active catalysts for metathesis of olefins were obtained through the interaction of bis(acetylacetonato)dioxymolybdenum(VI) with surface OH groups of -Al₂O₃ and subsequent reduction in H₂ or CO.

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()(VI) OH -Al₂O₃ H₂ CO .

     

Specificity of states of Cu2+ ions in ZSM zeolites due to the cooperative Jahn-Teller effect

Crystalline silicate of ZSM zeolite structure was synthesized via hydrothermal crystallization at large contents of copper. ESR spectra of Cu²⁺ ions stabilized in this system are determined by the specific ordering due to the cooperative Jahn-Teller effect of Cu²⁺ ions with the d_x ²–y² ground state.

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423° ZSM . Cu(II), , - Cu²⁺ cdx²–y²— .

     

Electronic influence of water adsorbed on ZnO in H2 and Co oxidation

In this paper we calculate the effect of surface OH/OH^– on the simultaneous adsorption of H₂ and O₂ on ZnO. A quantitative comparison between H₂ and CO oxidation rates shows that the two mechanisms are similar for the same water recovery on ZnO.

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OH/OH^– H₂ O₂ ZnO. H₂ CO , ZnO.

     

Interpretation of energy stability for Ti27+ and Ti26+ dimers

By using the interacting bonds method (IBM), it has been established that for the chloride Ziegler systems (TiCl₄+AlR₃) for polymerization the formation of Ti ₂ ⁷⁺ and Ti ₂ ⁶⁺ pairs is a thermodynamically favorable process.

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(TiCl₄+AlR₃) () , Ti ₂ ⁷⁺ Ti ₂ ⁶⁺ .

     

H2O? radicals trapped in Y-type zeolites

The results of CHDO/SP calculations do not support the detection of H₂O^– ions in MgY and CaY zeolites.

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CNDO/SP H₂O^– MgY CaY.

     

Stopped-flow study of the oxidation of ascorbic acid by the oxo-bridged trinuclear ruthenium complex [(NH3)5RuORu(NH3)4 ORu(NH3)5]7+

The kinetics of the oxidation of ascorbic acid by [(NH₃)₅RuORu(NH₃)₄ORu(NH₃)₅]⁷⁺ has been studied by the stopped-flow method. The activation parameters have been calculated and a possible mechanism is suggested.

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[(NH₃)₅RuORu(NH₃)₄ORu·(NH₃)₅]⁷⁺ . .

     

Partial oxidation of methane on Cr2O3/Al2O3

The oxidation of methane on supported chromia was studied at temperatures varying between 423 and 743 K and CH₄/O₂ ratios between 1 and 9 in a differential reactor. The main reaction products observed were carbon monoxide and formaldehyde. The rates of reaction obey a power law expression.

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, 423 743 CH₄/O₂ 1 9, . . .

     

Cyclohexene skeletal isomerization activity of sepiolites modified with B3+ or Al3+ ions

The effect of sepiolite modification by B³⁺ and Al³⁺ ions on catalytic performance were investigated in cyclohexene skeletal isomerization (CSI) reaction. Catalytic activity to 1- and 3-methylcyclopentenes (1- and 3-MCP) fit the Bassett-Habgood kinetic model for first order processes. These ions induced strong acidity in the sepiolite and the best results (greater activity and selectivity to 1-MCP) were found when the sepiolite was exchanged with an BF₃/methanol solution which contained 3 wt.% of the B³⁺ ion.

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B³⁺ Al³⁺ . 1- 3- - . . - 1-- , BF₃/, 3 . % B³⁺.

     

Decomposition of dimethyl sulfide in the presence of Al2O3, and catalyst deactivation

The catalytic decomposition of dimethyl sulfide has been studied over the temperature range of 400–500 °C. The main reaction products are methylmercaptane, H₂S and methane. Catalyst deactivation is due to its coking during the reaction. The possibility of oxidative catalyst regeneration at 550 °C has been shown.

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400–500°C. , . , . 550°C.

     

Coke deposits on Pt/Al2O3 catalysts of varying dispersities

Coke deposition during cyclopentane reaction was investigated on Pt/Al₂O₃ catalysts of varying dispersity. For all working pressures the higher the metallic accessibility, the higher the amount of coke deposited on the catalyst. Nevertheless, coke deposited on the less dispersed catalysts is more toxic for the metallic function. An increasing metal accessibility improves the graphitization of coke on the support and so, prevent the deactivation of the metal of a bifunctional catalyst.

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Pt/Al₂O₃ . , , , . , , , . , .

     

Liquid phase CO+H2 reactions in presence of ruthenium catalysts

Several effects on the hydrogenation of carbon monoxide in propanol in presence of ruthenium catalysts are examined. The homologation reaction is not observed, only propyl formate and propyl acetate are produced with any ruthenium catalyst. The pH-value is an important parameter: in acid media, the yield of propyl formate is noticeably increased indicating different catalytic active species. The addition of cesium salts is also benefitial for formate formation. This is not the case when water is associated with propanol as solvent. Finally, no ethylene glycol is detected. The process is found to be homogeneous and methanol seems to be the precursor of methyl formate.

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, . , . : , . . , . . , -, .

     

Synthesis and studies of catalysts prepared by supporting Hf(CH2Ph)4 on SiO2 and Al2O3

Catalysts prepared by supporting Hf(CH₂Ph)₄ on silica and alumina were studied. Their catalytic activity in ethylene polymerization was shown to increase considerably upon heating in hydrogen. IR spectroscopic studies of catalysts heated in hydrogen show the formation of surface Hf hydrides.

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, Hf (CH₂Ph)₄ . , . .