51V-NMR spectra of vanadates and oxosulfato-vanadates of alkali metals

A relation between the type of vanadium environment and the chemical shift anisotropy in the⁵¹V-NMR spectra has been established. The results obtained are compared with spectra of real catalysts.

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⁵¹V , .

     

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 ) .

     

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, . . .

     

Catalytic conversion of 2-propanol on La2MnZnO6

The perovskite La₂MnZnO₆ has been synthesized by a ceramic technique and its catalytic activity has been tested for 2-propanol decomposition. The catalyst is totally selective to dehydrogenation of the alcohol. A possible mechanism for the reaction is proposed.

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La₂MnZnO₆ 2-. . .

     

Observation conditions and thermal stability of O2? on SnO2

A sharp change in the relaxational characteristics of O ₂ ^– anion radicals on SnO₂ is observed under physical adsorption of O₂ molecules in an amount less than 10¹⁶ m^–3. The thermal stability of sites for O ₂ ^– stabilization on SnO₂ is analyzed. Molecular oxygen, forming O₂, is shown to desorb with increasing temperature without participating in reoxidation of the oxide.

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O ₂ ^– SnO₂ O₂ 10¹⁶ M^–2. O ₂ ^– SnO₂. , O₂, O ₂ ^– , .

     

Application of the Singh-Jha equation in the evaluation of b* of the Laidler-Landskroener equation

The least distance of the closest approach, b^*, of the Laidler-Landskroener equation has been evaluated by application of the Singh-Jha equation in case of acid catalyzed hydrolysis of benzyl formate in water-DMSO solvent system. The values obtained are quite reasonable.

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- , -. .

     

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.

     

Catalytic decomposition of N2O on La2Cu0.5M0.5O4 (M=Co, Ni, Cu and Zn)

Decomposition of N₂O has been studied over La₂Cu_0.5M_0.5O₄ (M=Co, Ni, Cu and Zn) between 380 and 485°C at 50 torr initial pressure of N₂O to understand the mutual interaction of two different active metal ions of the same concentration and valence in deciding the physico-chemical and catalytic properties. A multicenter type of adsorption of N₂O has been visualized and it is found that the rate is governed by the electronic factor.

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N₂O La₂Cu_0,5M_0,5O₄ (M=Co, Ni, Cu Zn) 380–485°C N₂O, 50 . , - . N₂O. .

     

Effect of iron on the behavior of Fe2O3?MoO3/SiO2 ammoxidation catalysts

Catalytic ammoxidation of propylene was studied using Fe₂O₃–MoO₃/SiO₂ catalysts, which have been prepared following a special method. Interaction of ammonia with the catalysts was studied by means of IR spectroscopy and gravimetrically using a McBain balance. Introduction of iron into MoO₃/SiO₂ catalysts modifies acidic as well as redox properties.

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Fe₂O₃–MoO₃/SiO₂ . . - . MoO₃/SiO₂ , .

     

Sensitization of the photoadsorption of O2 and NO on SnO2

Photoadsorption activity of SnO₂ with respect to O₂ and NO after CO chemisorption has been revealed to be drastically increased. Photoadsorption is suggested to be sensitized by surface carbonates formed due to CO chemisorption.

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. , .

     

Hydrogenation of CO2

The hydrogenation of CO₂ has been studied on three different series of catalysts: Fe/MgO, Ni/Ti, Cr/Zn doped with potassium. Reaction was carried out in a conventional flow microreactor system at 15 bar at 250–350°C. Three independent competing reactions: Reverse gas-water shift (RGWS), Fischer-Tropsch (FT) and methanol synthesis were observed.

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CO₂ : Fe/MgO, Ni/Ti, Cr/Zn . 15 250–350°C. : RGWS, F.T. .

     

Comparison of the sulfurization of CoMoK/Al2O3 catalyst with H2S and CS2

Only H₂S consumption and H₂O formation was found in the sulfurization of CoMoK/Al₂O₃ water gas shift catalyst with H₂S/H₂, but CO₂ was formed first, then CH₄, H₂O and H₂S appeared in the later part of TPS with CS₂/H₂. Carbon deposition on the catalyst during the sulfurization with CS₂/H₂ caused a lower activity than the catalyst sulfurized with H₂S but could be removed in the run of WGS reaction.

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, CoMoK/Al₂O₃, H₂S/H₂ H₂S H₂O, CS₂/H₂ CO₂ CH₄, H₂O H₂S. CS₂/H₂ H₂S, , .

     

Electroconductivity changes of Na-modified TiO2 and Pt/TiO2 films

Electrolytic supporting of metallic sodium on the surface of TiO₂ and Pt/TiO₂ films is shown to change significantly the Fermi level of the semiconductor substrate already at small concentrations of sodium. The steady-state catalytic activity changes only at high concentrations of supported sodium, varying the chemical composition of the active phase. The contact process does not play any significant role in the catalytic process.

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, TiO₂ Pt/TiO₂ . , . .

     

Effect of rare earth ions on the catalytic activity of Ln2MnNiO6 perovskites

Abstract A series of rare earth transition metal perovskites has been synthesized and the catalytic activity tested for 2-propanol decomposition. The effect of rare earth ions on the catalytic activity can been understood from the correlations obtained between the physico-chemical properties and the catalytic activity of the perovskites.

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, , 2-. , - .

     

Non-catalyzed oscillation reaction in aniline-KBrO3?H2SO4 system, I. Potentiometric study of oscillations

The non-catalyzed oscillation reaction of the aniline-KBrO₃–H₂SO₄ system has been followed potentiometrically. The concentration regions of the beginning of oscillation are given in a triangular diagram. Also studied was the dependence of the induction period on concentration of the participants, which was described by a kinetic equation. The oscillation region extends to lower KBrO₃ concentrations, the number of the oscillation jumps increases, and the induction period is shortened with increasing acidity.

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-KBrO₃–H₂SO₄. . . KBrO₃, .

     

Stereoselectivity observed in cross metathesis of cis- and trans-2-butene with 1-butene over Re2O7/Al2O3 catalyst

Cross metathesis of cis- and trans-2-butene with 1-butene was studied over Re₂O₇/Al₂O₃ catalyst in a recirculation system at 313 K. Formation of ethylene and hexenes was inhibited by 2-butenes; formation of propene and pentene proceeded without induction from trans- and with induction from cis-2-butene and 1-butene. Selective formation of trans-2-pentene was observed from trans-2-butene, but no such selectivity was characteristic for cis-isomers.

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- -2- 1- Re₂O₇/Al₂O₃ 313 . 2-; - -2- 1-. -2 -2-, , - .

     

On the deactivation of Fe2O3?MoO3/SiO2 catalysts in the oxidation of methanol to formaldehyde

The deactivation behavior of Fe₂O₃–MoO₃/SiO₂ catalysts with different Fe₂O₃+MoO₃ content in the oxidation of methanol to formaldehyde is investigated. A simplified reaction-deactivation kinetic model is presented and used to compare and discuss the different behaviors.

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Fe₂O₃–MoO₃/SiO₂ Fe₂O₃+MoO₃ . : -.

     

Effect of the metal atom of acetylacetonates on the autoxidation of cumene

The oxidation of cumene and a cumene-nitrobenzene (12) mixture at 60°C in the presence of AIBN and acetylacetonates of Co(II), Cu(II), Fe(II), Fe(III), V(III), Cr(III), Mn(III) and MoO ₂ ²⁺ has been investigated.

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(12) 60°C - Co(II), Cu(II), Fe(II), Fe(III), V(III), Cr(III), Mn(III), MoO ₂ ⁺² .

     

Polarity of the transformation processes in thermal measuring systems

The temporal relativistic principle, recently established for calorimetric systems in the framework of the theory of the topoenergetic behaviour of composite systems, is extended to general thermal measuring systems. A thermal measuring system is defined as a measuring system in which the conversion of a response function is measured as a result of a stepwise perturbation in temperature. The process of crystallization revealed by different thermal measuring systems is considered for a series of compounds for which the processes are identical in nature, but differ in amplitude, so that an external affine relationE=n K + m is verified between the activation energyE and the amplitude termK. It results that the polarity of a transformation process is a characteristic proper to the temporal reference system of the considered measuring system and can be expressed by the signs of the parametersE and/orn.

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Zusammenfassung Das gemäßigte relativistische Prinzip das unlängst für die kalorimetrischen Systeme im Rahmen der Theorie des topoenergetischen Verhaltens der zusammengesetzten Systeme festgelegt worden ist, wird auf allgemeine thermische Meßsysteme ausgedehnt. Ein thermisches Meßsystem wird als ein Meßsystem definiert, in dem die Umwandlung einer Antwortfunktion als Ergebnis einer stufen weisen Temperaturstörung gemessen wird. Der durch verschiedene thermische Meßysteme bestimmte Kristallisationsverlauf wird als eine Serie von Mischungen betrachtet, für welche die Beschaffenheit des Vorganges identisch, jedoch die Amplituden verschieden sind, so daß eine externe AffinitätsbeziehungE=n K + m zwischen der AktivierungsenergieE und dem AmplitudenausdruckK erfüllt werden kann. Es ergibt sich, daß die Polarität eines Umwandlungsprozesses charakteristisch für das temporale Bezugs-system des betreffenden Meßsystems ist und durch das Zeichen der ParameterE und/odern ausgedrückt werden kann.

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, , . . , , , , . - E=nK+m . , E ( ).