Preparation of a Ru/Al2O3 catalyst from Ru3(CO)12 infrared and XPS study

A supported ruthenium catalyst on alumina prepared from Ru₃(CO)₁₂ has been studied by infrared and X-ray photoelectron spectroscopy (XPS). The triatomic cluster is retained on the support but breaks down at 150°C. Complete elimination of the carbonyl groups requires heating at 350°C under vacuum. XPS studies show that the decomposed catalyst does not change on further reduction in H₂ at 400°C. The ruthenium atoms remain trapped within the pores of the support.

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Al₂O₃, Ru₃(CO)₁₂, (XPS). , 150°C . 350°C . XPS , H₂ 400°C . .

     

An alternating pulse current technique for potentiometric stripping analysis (APC-PSA)

The response signal in PSA measurements – the transition time – can be considerably amplified by using a special pulse technique which we call alternating pulse current (APC). The sensitivity of the method is thereby considerably increased. This is achieved by modulating the current with a high frequency in a square wave mode during the stripping phase in such a way, that cathodic and anodic pulses alternate, so that the species to be determined is stripped and – at least partially – redeposited during the procedure. The transition time is not affected by the absolute values of the currents and of the times they flow. The amplification is determined by their respective ratios only. The equations holding are derived and proven experimentally by measurements on very dilute Pb solutions. The APC-PSA technique has also been applied for systems termed irreversible such as U and Tc, where also a considerable amplification could be achieved. The probable reasons are discussed and future developments and investigations are depicted.     

Electronic spectral study of the interaction of CoNaX zeolite with C1?C5 hydrocarbons

Interaction of both satured and unsaturated hydrocarbons with tetrahedral Co²⁺ ion complexes lodged in the zeolite skeleton is reported on the basis of diffuse reflectance spectra. While saturated hydrocarbons do not affect the coordination sphere of the Co-complex, the unsaturated hydrocarbons change considerably the distortion of the tetrahedral Co-complex.

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- Co²⁺ - . - Co-, - - Co-.

     

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, . . .

     

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, , .

     

Structure sensitivity and coke formation on Pt/Al2O3 catalysts

The initial rate of carbon formation during cyclopentane reaction has been studied on different Pt/Al₂O₃ catalysts of varying metal dispersity. It has been shown that coke deposition on the metal is a structure sensitive reaction which is preferably produced on large metallic particles. On the other hand, coke deposition on the whole catalyst is relevant to cyclopentadiene formation and is a structure insensitive reaction since the initial rate of coke deposition on the whole catalyst is proportional to the metallic surface area.

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Pt/Al₂O₃ . , , . , , , .. .

     

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 ) .

     

Kinetic studies of Pt/Al2O3 catalyst pellets with nonuniform activity

Catalysts with nonuniform distribution of the catalytically active component (Pt) over their porous support (Al₂O₃) have been studied. A nonuniform activity distribution changes not only the reaction rate but also the kinetics can be different on these catalysts.

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(Pt) (Al₂O₃). , , .

     

Chlorination of V2O5 by CCl4. The proposed reaction mechanism

Initial stage of the reaction of CCl₄ with V₂O₅ has been studied by MS and XPS techniques. According to the proposed mechanism dissociatively chemisorbed CCl₄ transforms to CO₂ via adsorbed COCl₂, while surface vanadium atoms involved are gaining step by step two chlorine atoms before the formation of the volatile end-product VOCl₃.

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CCl₄ V₂O₅ . - CCl₄ CO₂ COCl₂, VOCl₃.

     

Temperature-programmed reduction of bimetallic Ir?Fe/Al2O3 catalysts

Investigations on the temperature-programmed reduction of 3% Ir–Fe/Al₂O₃ catalysts after their oxidation at different temperatures T_ox have been carried out. A substantial promoting effect of iridium on the reducibility of iron has been observed for all the investigated catalysts, at T_ox applied.

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- 3% Ir–Fe/Al₂O₃ (T_ox). T_ox.

     

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.

     

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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. , .

     

Thermal decomposition of tetraamineplatinum(II) chloride by simultaneous TG/DTG/DTA/MS and direct insertion probe mass spectrometry

Simultaneous thermogravimetry (TG), derivative thermogravimetry (DTG), differential thermal analysis (DTA), and evolved gas analysis (EGA) by mass spectrometry (MS) have been used to determine the decomposition path for tetraamineplatinum(II) chloride and cis- and trans-diamineplatinum(II) chloride. Unequivocal identification of the evolved gases was done by direct insertion probe mass spectrometry.The thermal decomposition of (NH₃)₄PtCl₂ occurred in two steps. The first was endothermic loss of two moles of ammonia producing a mixture of cis- and trans-diaamineplatinum(II) chloride. The second step was decomposition of the diamine complex to metallic Pt and N₂, HCl, and NH₄Cl. Reduction of Pt(II) to metallic Pt was coupled with oxidation of ammonia to molecular nitrogen and protons.

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Zusammenfassung Simultane Thermogravimetrie (TG), derivative Thermogravimetrie (DTG), Differentialthermoanalyse (DTA) und Analyse der entwickelten Gase (EGA) durch Massenspektrometrie (MS) wurden zur Bestimmung des Reaktionsverlaufs bei Zersetzung von Tetraminplatin(II)-chlorid sowie cis- und trans-Diaminplatin(II)-chlorid herangezogen. Die eindeutige Identifizierung der entwickelten Gase erfolgte durch Massenspektrometrie mit direkter Probeneinführung. Die thermische Zersetzung von (NH₃)₄PtCl₂ erfolgt in zwei Schritten. Der erste ist die endotherme Abspaltung von zwei Mol Ammoniak unter Bildung eines Gemisches von cis- und trans-Diamin-platin(II)-chlorid. Der zweite Schritt ist die Zersetzung des Diaminkomplexes zu metallischem Pt, H₂, HCl und NH₄Cl. Die Reduktion von Pt(II) zu metallischem Pt ist mit der Oxydation von Ammoniak zu molekularem Stickstoff und Protonen gekoppelt.

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-, -, -, - - (II) - (II) . (II). -. (NH₃)₄PtCl₂ . - -(NHN₃)₂PtCl₂. , , . .

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The technical assistance of G. J. Dechert is gratefully acknowledged.     

Structure of Pt/ZnAl2O4 catalysts

The effect of the support preparation technique (solgel and coprecipitation) on the final Pt/ZnAl₂O₄ catalyst is presented. The structural properties of the solids obtained are correlated to the selectivity and activity for isobutane dehydrogenation in H₂ and He reaction media. If a highly dispersed catalyst is suitable, the support has to be prepared by the sol-gel method.

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( — ) Pt/ZnAl₂O₄. H₂ He. , — .

     

51V NMR studies of systems V2O5-KHSO4 and V2O5?K2SO4

Systems V₂O₅–KHSO₄ and V₂O₅–K₂SO₄ have been studied by the⁵¹V NMR method. The first system demonstrates the same states of vanadium as the previously studied V₂O₅–K₂S₂O₇, in this system a compound with an equimolar ratio of components has been found. In V₂O₅–K₂SO₄ the state of vanadium differs from the above systems and the formation of a compound with V/K=4 is observed.

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⁵¹V KHSO₄–V₂O₅ K₂SO₄–V₂O₅. , K₂S₂O₇–V₂O₅, . K₂SO₄–V₂O₅ V/K4.

     

Thermal activation of Al2O3 supported MoO3 and WO3 metathesis catalysts

Alumina-supported MoO₃ and WO₃ catalysts were activated for the metathesis of propene by thermal treatment in Ar. Temperatures up to 1140 K are required for catalysts with low metal contents. These exhibit the highest specific activities though they are known to be highly resistant to reduction. It is proposed that the active sites are formed from Mo(VI) and W(VI) species under the conditions employed.

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MoO₃ WO₃, Al₂O₃, . 1140 . , , . , , Mo W.

     

Liquid phase oxidation of benzene to phenol over K2Cr2O7/SiO2

MoO₃/Al₂O₃ is reduced at least partly by sulfur which is formed from H₂S in sulfidation with H₂S/N₂ mixture. SO₂ formation during TPD of MoO₃/Al₂O₃ with presorbed H₂S provides evidence for the explanation.

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MoO₃/Al₂O₃ , H₂S/N₂. SO₂ MoO₃/Al₂O₃, H₂S, .

     

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-. , - .

     

Influence of the preparation method on the pore spectrum of Pt?Cr/Al2O3 and Pt?Sn/Al2O3 catalysts

It is shown that, in contrast to classical impregnation methods, in bimetallic catalyst production the texture of the carrier is stabilized by introducing the promoting ion on the surface of Pt/Al₂O₃ with vapors of CrO₂Cl₂ or SnCl₄. This is shown by a relatively slower decrease of the specific area and the volume of the pores upon calcination.

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, Pt/Al₂O₃- CrO₂Cl₂ SnCl₄ . .

     

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, .