Reactions of C4?C6 alkanes on platinum and platium-gold films

Results are reported on the reactions of n-butane, n-pentane and n-hexane on Pt and Pt/Au alloy films. The results are compared with those obtained for Pt–Au alloys on a SiO₂ carrier. It is concluded that alloying can change the selectivity of the catalyst. No indication has been found for the possible role of oxygen in the high selectivity of Pt in non-destructive reactions.

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-, - - Pt . , Pt–Au SiO₂. , . - Pt .

     

Kinetic models of CO oxidation on Pd-containing catalysts (with and without SO2)

The effect of reactants and experimental conditions on the Pd/C catalyzed oxidation of DS at 110–150°C and 0.3–1.0 MPa in alkaline aqueous solution is described with emphasis on the maximal reaction rate, yield of DGA and catalyst deactivation. Oxygen causes practically irreversible deactivation of catalyst.

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DS Pd/C 110–150°C 0.3–1.0 . , DGA . .

     

CO and NO adsorption on photoreduced Mo/SiO2 catalysts

CO and NO adsorption on photoreduced Mo/SiO₂ catalysts has been studied by IR and mass-spectrometric methods. Products of interaction between adsorbed molecules and surface molybdates of various structures have been identified.

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- - CO NO CO Mo/SiO₂ . .

     

FTIR investigation of the structure of vanadium oxides on ZrO2 and oxidation of toluene on it

The oxidation of toluene has been studied on V₂O₅/ZrO₂ by both FTIR spectroscopy and pulse method. The results suggest that Lewis-acidic sites play a significant role in the formation of benzaldehyde from toluene.

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V₂O₅/ZrO₂ - , . .

     

Kinetics and selectivity of the oxidation of alkanes in Cl2?H2O and Cl2?Hg2+?H2O solutions

Relative oxidation rate constants of several normal, iso-, cyclo-and methylcycloalkanes have been measured in Cl₂–H₂O and Cl₂–Hg²⁺–H₂O solutions at 343K. The selectivity of C–H bond dissociation in both systems is the same. HOCl is assumed to be the active species for the two systems.

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Cl₂–H₂O Cl₂–Hg²⁺–H₂O 343 , -,- ; C–H . , HOCl.

     

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

     

Temperature dependences of hydrogen kinetic isotope effect in reactions of cyclohexane with Mn(VII), Cr(VI) and NO2+ in solutions

Temperature dependences of hydrogen kinetic isotope effect (KIE) in reactions of cyclohexane with Mn(VII), Cr(VI) and NO ₂ ⁺ in solutions have been studied. With increasing temperature from –10° to 140°C, KIE decreases and the equation k_H/k_D=A_H/A_Dexp(E/RT) is met.

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() Mn(VII), Cr(VI) NO ₂ ⁺ . –10° 140°C , k_H/k_D=A_H/A_Dexp(E/RT).

     

Effect of vanadium content on the character of acidic sites on V2O5/Al2O3 catalysts

By IR spectroscopy and TPD the effect of vanadium content on the relative proportion of strongly acidic sites of V₂O₅/Al₂O₃ catalyst was studied.

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- - V₂O₅/Al₂O₃.

     

Effects of tempering time and tempering temperature of caustic mercerization on the spectral and electrical properties of Egyptian cotton fibres

Several samples of Egyptian cotton fabric strips were subjected to various caustic mercerization conditions, varying in temperature and time. On these samples extensive measurements were undertaken, comprising X-ray diffraction, IR absorption spectra and the temperature-dependence of DC-electric conductivity.The phase constitution, % crystallinity, IR band assignment, activation energies for conduction and energy gap were evaluated as a function of caustic mercerization. The results obtained were correlated and discussed in detail, leading to valuable information of use in the cotton fabric strip industries.

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Zusammenfassung Verschiedene Proben von ägyptischen Baumwollstreifen wurden unter verschiedenen Bedingungen (Temperatur, Zeit) einer Laugung unterworfen. Die gelaugten Proben wurden eingehend durch Röntgendiffraktometrie, IR-Absorptionsspektroskopie und Messungen der Temperaturabhängigkeit der elektrischen Gleichstromleitfähigkeit untersucht. Phasenstruktur, Kristallinität, Zuordnung der Banden, Aktivierungsenergien für die Leitfähigkeit und verbotene Bänder wurden in Abhängigkeit von der Laugung ermittelt. Die erhaltenen Ergebnisse wurden miteinander verglichen und in Einzelheiten diskutiert, wobei für die Baumwollverarbeitungsindustrie wertvolle und empfehlenswerte Informationen erhalten wurden.

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. , . , , , . , .

     

Dispersity and reducibility of the molybdenum oxide phase in SiO2, SiO2?Al2O3 and γ-Al2O3 supported molybdena catalysts

XRD, isothermal and temperature-programmed reduction (TPR) experiments were carried out with SiO₂, SiO₂–Al₂O₃ and -Al₂O₃ supported catalysts. Molybdena is in a more disperse state on supports containing more alumina and it is more reducible on SiO₂–Al₂O₃ than on SiO₂ or -Al₂O₃. TPR curves were shown to reflect connections between reduction kinetics and dispersity.

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-, , SiO₂, SiO₂–Al₂O₃ -Al₂O₃. , , SiO₂–Al₂O₃ SiO₂ -Al₂O₃. .

     

Studies of the reactions of Br(2P3/2) and Br(2P1/2) with SiH4

Photobromination of SiH₄ under uv-irradiation at various wavelengths has been studied. Rate constants for the elementary reactions Br(²P_3/2)+SiH₄HBr+SiH₃ (k=3.2×10^–11 exp(–21.8±2.5)/RT, cm³/s) and Br^* (²P_1/2)+SiH₄HBr+SiH₃ (k^*=(3±1)×10^–13 cm³/s) have been determined in the temperature range from 300 to 415 K.

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- . Br(²P_3/2)+SiH₄HBr+SiH₃, k=3,2×10^–11 exp (–21,8±2,5)/RT ³/ Br^*(²P_1/2)+SiH₄HBr+SiH₃, k^*=(3±1)×10^{–13 3}/ 300–415 K.

     

HCN synthesis from NH3 and CH4 on Rh and Ir

The synthesis of hydrocyanic acid from methane and ammonia on Rh and Ir wires was studied at temperatures varying between 1200 and 1500 K at one atmosphere. Activation energies and preexponential factors are reported.

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1200–1500K . .

     

Influence of chemical non-steady-state on SO2 conversion in fluidized catalyst bed

The effect of the influence of catalyst non-steady-state on SO₂ conversion ion a fluidized catalyst bed has been studied depending on the ratio of relaxation time for the catalytic reaction step to the characteristic time of particles diffusion.

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.

     

Valence state and coordination number of molybdenum supported on SiO2 or MgO during the oxidation of propylene

The nature of the species occurring during the oxidation of propylene on molybdenum oxides supported on silica or magnesia has been investigated by diffuse reflectance spectroscopy. The reaction was performed in the uv cell itself. The oxidation occurs on partially reduced solids and the selectivity for acrolein is related to tetrahedral Mo⁵⁺.

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, , . . . Mo⁺⁵.

     

Catalytic activity of perovskite-type oxides LaMeO3

Catalytic activities for CO oxidation of a series of LaMeO₃(Me³⁺=V³⁺, Cr³⁺, Mn³⁺, Fe³⁺, Co³⁺, Ni³⁺) perovskite-type oxides were measured. Maxima for Mn³⁺ and Co³⁺ were found. The relation between local symmetry of solid surfaces and chemisorption and catalysis is discussed.

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, LaMeO₃ (Me⁺³=V⁺³, Cr⁺³, Mn⁺³, Fe⁺³, Co⁺³, Ni⁺³) CO. Mn⁺³ Co⁺³. , .

     

Temperature-programmed hydrogen desorption from water on bimetallic catalysts Ir?Fe/Al2O3

Desorption of hydrogen liberated in the process of water decomposition on bimetallic catalysts (3% Ir–Fe/Al₂O₃) at linear temperature growth was observed. In the case of iridium the amounts of desorbing hydrogen are relatively small, whereas for iron they are many times greater.

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, 3% Ir–Fe/Al₂O₃ . , , .

     

Unsteady-state performance of NOx catalytic reduction by NH3

Experimental results of studying NO_x catalytic reduction by NH₃ under periodic reversals in the direction of filtration of the mixture purified in a catalyst bed are discussed.

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NO_x .

     

CO oxidation over CuCr/Al2O3 catalysts in presence of SO2

Poisoning of variously prepared CuCr/Al₂O₃ catalysts having different compositions by sulfur dioxide has been studied. Comparative values for a decrease in the catalyst activities have been obtained.

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CO .

     

[Fe(phen)3]2+ aquation in aqueous polyacrylamide solution

The aquation of tris(1, 10-phenanthroline) iron(II) has been studied in aqueous polyacrylamide solutions. The rate increases up to 2.8 times at low polymer concentrations, and subsequently decreases. These effects are attributed to changes in the local water activity in the region of the complex.

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(1, 10-) (II) . 2,8 , . .

     

Calculation of recombination rate constants in (H2?O2) system

Rate constants of the three-body recombination for the elementary three-molecule stages in hydrogen oxydation have been calculated.

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, .