Kinetics of oxidation of octacyanomolybdate(V) ion by thiosulfate

The oxidation of thiosulfate by octacyanomolybdate(V) in the pH range of 4,0 to 5,1 is catalyzed by alkali metal ions and shows first order dependence on the concentrations of thiosulfate, octacyanomolybdate(V) and alkali metal ions and is independent of the hydrogen ion concentration. A mechanism for the reaction is proposed.

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(V) pH=4,0–5,1 . , (V) . . .

     

Formation of N-butane in the pyrolysis of ethylene [1]

Yields of n-C₄H₁₀ have been measured from the flow pyrolysis of C₂H₄ at 897 (±7) K. From 77 to 720 Torr the order of n-C₄H₁₀ formation was found to be 2.0±0.3 The rate constant for the reaction, was estimated to be 2.4(±0.6)×10^–4l mol^–1s^–1.

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-C₄H₁₀ C₂H₄ 897 (±7) . -C₄H₁₀ 77 720 2.0±0.3. 2C₂H₄C₂H₃+C₂H₅ 2,4 (±0,6)×10^{–4 –1–1}.

     

Ultrasonic study of the molecular encapsulation and the micellization processes of dodecylethyldimethylammonium bromide-water solutions in the presence of β-cyclodextrin or 2,6-di-o-methyl-β-cyclodextrin

Aqueous solutions of -cyclodextrin (-CD) or 2,6-di-o-methyl--cyclodextrin (DM--CD) and dodecylethyldimethylammonium bromide (D₁₂EDMAB) have been studied from speed of sound (u) data at 298.15 K, using a pulse-echo-overlap technique. The molecular encapsulation process of the surfactant monomer into the cyclodextrin cavity and its effect in the micellization process of the surfactant have been analyzed from theu measurements: I) as a function of [D₁₂EDMAB] in the presence of several initial cyclodextrin concentrations (-CD or.DM--CD); II) as a function of [cyclodextrin] (-CD or DM--CD), for an initial micellar solution of D₁₂EDMAB and; III) as a function of the [cyclodextrin]/[surfactant] stoichiometric concentrations. Both inclusion complexes formed (-CDD₁₂EDMAB) and (DM--CDD₁₂EDMAB) have stoichiometries of 11, and their association constantK have been determined using a model proposed in this work, based on the additivity of the different contributions of the involved species to the speed of sound. The apparent critical micellar concentration, cmc^*, of D₁₂EDMAB is found to increase linearly upon the addition of cyclodextrin (-CD or DM--CD). The free surfactant concentration in the micellar region, [D₁₂EDMAB]_f, decreases in the presence of -CD and slightly increases in the presence of DM--CD. The influence of the parcial methylation of the -cyclodextrin (-CDDM--CD) and of the polar head of the surfactant (D₁₂TAB D₁₂EDMAB) on the complextion and micellar parameters are also discussed.Supplementary material available: Tables of speed of sound (14 pages) are available from the authors.     

Heterogeneous reactions of solid nickel(II) complexes

The influence of different modes of preparation on the stoichiometry of thermal decomposition of isothiocyanatonickel(II) complexes with ammonia was studied. It was found that the complex Ni(NCS)₂(NH₃)₄ (I) prepared by heterogeneous reaction undergoes decomposition in two steps (–2 NH₃, –2 NH₃), while for complex II, of the same composition but prepared by homogeneous reaction from solution, the decomposition proceeds in three steps (–1 NH₃, –1 NH₃, –2NH₃). Electronic and infrared absorption spectra were used for the study of the spectral properties of the starting complex. It was found that the different stoichiometries of thermal decompositions of complexes I and II do not cause differences in the bonding strength of the ammonia molecules (chemical factor); this effect is rather brought about by physical factors such as different imperfections of the crystal lattice.

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Zusammenfassung Der Einfluß der Herstellung auf die Stöchiometrie der thermischen Zersetzung von Amin-Komplexen des Isothiocyanatonickels wurde studiert. Der Zerfall des Komplexes Ni(NCS)₂(NH₃)₄ (I), hergestellt durch heterogene Reaktion, verlief in zwei Etappen (–2 NH₃, –2 NH₃). Beim selben Komplex (II), hergestellt durch homogene Reaktion in Lösung, wurden jedoch drei Etappen beobachtet (–1 NH₃, –1 NH₃, –2 NH₃). Die Eigenschaften des Ausgangsproduktes wurden durch Elektronen- und IR-Spektroskopie untersucht. Das unterschiedliche thermische Verhalten ist nicht auf eine verschiedene Bindungsstärke der NH₃ Moleküle, sondern auf physikalische Ursachen, wie z. B. Unregelmässigkeiten im Kristallgitter zurückzuführen.

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Résumé On a étudié l'influence des diverses méthodes de préparation sur la stoechiométrie de la réaction de décomposition thermique des complexes de l'isothiocyanate de nickel(II) avec l'ammoniac. On a établi que le complexe Ni(SCN)₂(NH₃)₄, (I), préparé rar réaction hétérogène, subit une décomposition en deux étapes (–2NH₃, –2NH₃), tandis que le complexe (II), de même composition, mais préparé par réaction homogène, à partir de solutions, se décompose en trois étapes (–1NH₃,–1NH₃, –2NH₃). Les propriétés spectrales du complexe initial ont été étudiées par absorption électronique et infrarouge. On a trouvé que les différences de stoechiométrie des réactions de décomposition thermique des complexes (I) et (II) n'apportaient pas de différences entre les énergies de liaison des molécules d'ammoniac (facteur chimique). C'est plutôt à des facteurs physiques, comme les différentes imperfections du réseau cristallin, que cet effet serait dû.

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(II) . , Ni(NCS)₂(NH₃)₄ (I), , (–2NH₃,–2NH₃). , II , , (–1 NH₃,–1 NH₃ –2NH₃). . , I II ( ), , .

     

Reaction of ammonium sulphate with aluminium oxide

The reaction between ammonium sulphate with aluminium oxide was studied. It was confirmed by X-ray diffraction and chemical analysis that three intermediate reaction products, (NH₄)₃Al(SO₄)₃, NH₄Al(SO₄)₂ and Al₂(SO₄)₃, are formed. The thermal decompositions of these three compounds were carried out. It has been shown that the same rate law is valid for them. The activation energies for (NH₄)₃Al(SO₄)₃, NH₄Al(SO₄)₂ and Al₂(SO₄)₃ are 95.9, 177.9 and 291.0 kj/mol, respectively.

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Zusammenfassung Die Reaktion von Ammoniumsulfat mit Aluminiumoxid wurde untersucht. Durch Röntgendiffraktion und chemische Analyse wurde bestätigt, daß drei Zwischenprodukte (NH₄)₃Al(SO₄)₃, NH₄Al(SO₄)₂ und Al₂(SO₄)₃ gebildet werden. Die thermische Zersetzung der drei Verbindungen wurde durchgeführt. Es wurde gezeigt, daß für alle drei dasselbe Geschwindigkeitsgesetz Gültigkeit hat. Die Aktivierungsenergien für (NH₄)₃Al(SO₄)₃, NH₄Al(SO₄)₂ und Al₂(SO₄)₃ sind 95.9, 177.9 und 291.0 kJ/Mol.

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. - : (NH₄)₃Al(SO₄)₃, NH₄Al(SO₄)₂ Al₂(SO₄)₃. , , . (NH₄)₃Al(SO₄)₃, NH₄Al(SO₄)₂ Al₂(SO₄)₃, , 95.9; 177.9 291.0 . ^–1.

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The authors are grateful to Dr. H. Osada and Mr. H. Nakamura, Department of Environmental Engineering, Kyushu Institute of Technology, for their helpful discussions.     

CO/H2 and CO2/H2 reactions with amorphous carbon-metal catalysts

By metal impregnation of selected naturally occurring organic materials followed by controlled carbonization, metal semicoke catalysts can be readily prepared. These catalysts have been tested in the synthesis of hydrocarbons and alcohols from CO/H₂ and CO₂/H₂ mixtures. Fe and Co preparations have been used. Relatively high temperatures are required when using these catalysts, which are quite active for synthesis using CO₂ and H₂. The pressure (5150 kPa) is very favorable both for the synthesis of liquid hydrocarbons (C₅–C₃₀) and alcohols (C₁–C₅).

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. CO/H₂ CO₂/H₂. Fe Co. , CO₂ H₂. 5150 ) (C₅–C₃₀) (C₁–C₅).

     

m-Xylene conversion over dealuminated Y zeolites studied by the pulse method

m-Xylene conversion was studied over dealuminated Y type zeolites in hydrogen forms, SiO₂ to Al₂O₃ ratios were varied from 4.86 to 12.95.

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- . SiO₂/Al₂O₃ 4,86 12,95.

     

Temperature programmed reduction and oxidation of Ir/Al2O3 catalysts

3 % Ir/Al₂O₃ catalysts have been studied by means of temperature programmed reduction and oxidation. With growing degree of metal oxidation (higher T_ox) reducibility of the catalysts at low temperatures decreases.

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3% Ir/Al₂O₃ . ( ) .

     

Kinetics of heterogeneous catalytic hydroformylation of propylene on rhodium-cobalt catalysts. Reaction mechanism

Steady-state kinetics of combined heterogeneous catalytic hydrogenation and hydroformylation of propylene on Rh–Co-containing catalysts has been studied at atmospheric pressure and T=140–170 °C. A reaction mechanism is suggested. The kinetic model adequately describes all observations.

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- Rh–Co- 140–170 °C. . , .

     

SIMS studies of water vapor adsorption on polycrystalline rhodium

Studies of water vapor adsorption on polycrystalline Rh at T>315 K and P=(2–4)×10^–2 Pa indicate that water is adsorbed dissociatively to O_ads and O_ads through a molecularly adsorbed species. Desorption activation energy is 46 and 69 kJ/mol for molecular and dissociative species, respectively.

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Rh (2–4)·10^–2 . , O OH - . 46 /, -69 /.

     

Pt?Fe2O3 catalytic system for hydrogenation reactions

The effect of Fe₂O₃ additives on crotonaldehyde hydrogenation over group VIII metals has been studied. Iron oxide added to platinum black exerts a modifying effect on the reduction of the carbonyl group of croton-aldehyde inhibiting hydrogenation of the C=C bond conjugated with a C=O group.

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Fe₂O₃ VIII -. , , - , C=C , C=O-.

     

Studies of Cu?Ni supported catalysts for enantioselective hydrogenation

The effect of support content and composition of supported metal phase on the crystallite size, phase composition and catalytic properties of supported Ni and Cu–Ni catalysts has been investigated. It has been established that with increasing metal content, crystallite sizes and enantioselectivity increase. Copper added to Ni catalysts decreases metal phase dispersity and enantioselectivity.

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, , - . , . є .

     

Analysis of thermal desorption spectra of oxygen desorbed from rhodium

Thermal desorption spectra of oxygen desorbed from rhodium have been analyzed in terms of models accounting for the effect of lateral interactions between adsorbed particles and of their diffusion into the bulk of metal on the desorption kinetics of O₂. Complex configuration of these spectra is ascribed to the processes of formation/decomposition of surface Rh oxides and the diffusion of particles into the near-surface layers of metal and back to the surface.

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- , O₂ . - O₂ Rh - .

     

Strong H2 chemisorption on Al2O3 or SiO2 supported group VIII metals

Following hydrogen treatments at high temperature a decrease in hydrogen chemisorption at room temperature is observed in almost all group VIII elements supported on SiO₂ or Al₂O₃. The effect is attributed to self inhibition by strongly chemisorbed hydrogen on the metals.

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VIII , SiO₂ Al₂O₃. .

     

Quantitative parameters by thermoanalytical methods

The conditions and premises of the kinetic evaluation of thermoanalytical curves on the basis of chemical kinetics are demonstrated, and the limits of their availability are pointed out. For reactions with an unclear structural and chemical course, some appropriate definitions of terms are proposed.The possibilities of the use of the inflection points of the reaction rate versus time curve are presented. New methods of determination of kinetic parameters are described, including the ratio of the degrees of reactionx, the ratio of the reaction ratesx and the ratio of the tangent slopesx at these points.

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Zusammenfassung Bedingungen und Voraussetzungen der kinetischen Auswertung thermoanalytischer Meßkurven auf der Basis der chemischen Kinetik werden dargestellt, gleichzeitig wird auf die Grenzen ihrer Gültigkeit hingewiesen. Für Reaktionen mit unklarem chemischem oder strukturellem Ablauf werden geeignete neue Bezeichnungen definiert.Die Möglichkeit zur Verwendung der Wendepunkte der Kurve Reaktionsgeschwindigkeit gegen Zeit vorgestellt. Neue Methoden werden beschrieben, die zur Bestimmung kinetischer Parameter das Verhältnis der Umsätzex ₁ x ₂, das Verhältnis der Reaktionsgeschwindigkeitenx ₁/x ₂, und das Verhältnis der Tangentensteigungenx ₁/x ₂ an den Wendepunkten verwenden.

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. . . — . , (x), () () .

     

Structural studies of nickel-based Raney catalysts

Electron microscopy and Mössbauer spectroscopy studies of nickel-based Raney catalysts have revealed that the catalysts are formed through the successive aggregation of their structural elements. Catalyst particles are covered by a thin layer of nickel oxide.

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. , . .

     

Effect of magnetic order on the conductivity in Co-Zn ferrites

A series of samples in the system Co_1–xZn_xFe₂O₄ (x=0.3, 0.4, 0.6, 0.8 and 1) were prepared by the usual ceramic technique. The D. C. electrical resistivity and thermoelectric power were measured in the temperature range from room temperature up to about 600 K. Transition from the ferrimagnetic region to the paramagnetic region is accompanied by an increase in the activation energy by an amountE, which varies in the range 0.052–0.090 eV. The large values ofE obtained may be due to the fairly strong B-B exchange interaction in Co-Zn ferrites.

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Zusammenfassung Mittels üblicher Keramiktechniken wurden Proben des Systemes Co₁–xZn_xFe₂O₄ unterschiedlicher Zusammensetzung (x=0,3, 0,4, 0,6, 0,8, 1,0) dargestellt. Im Temperaturbereich Raumtemperatur-600 K wurde der elektrische Widerstand gegenüber Gleichstrom sowie die Thermospannung dieser Proben ermittelt. Der Übergang von der ferrimagnetischen zur paramagnetischen Region wird von einem Anwachsen der Aktivierungsenergie um den BetragE=0,052–0,090 eV begleitet. Den so erhaltenen grossen E-Werten liegen wahrscheinlich die ziemlich starken B-B Austausch Wechselwirkungen in Co-Zn Ferriten zu Grunde.

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_1–xZn_xFe₂₄ =0,3;0,4;0,6;0,8 1, 600 . E, 0,052–0,090 . E - - .

     

On theC p toC v conversion of solid linear macromolecules II

A modification is proposed for the Nernst-Lindemann equation that is used to convert calculated heat capacities at constant pressure (C _p ) to heat capacities at constant volume (C _v ) for solid, linear macromolecules. the constant A₀ per mole of repeating unit in this equation is derived by taking into account the variable number of vibrators excited at different temperatures. With the new equation it is possible to calculateC _p for solid polymers over a wider temperature range. The constant is calculated for solid polymers from experimental thermal expansivity, isothermal compressibility and heat capacity data obtained from the literature. An average value of (3.9±2.4)×10^–3(K mol)/J was obtained for A₀ (new) from data on 22 solid polymers. This average value may be used as a universal constant in case no experimental data on compressibility and expansivity are available for computation ofA ₀. The remaining variation of A₀ (new) with temperature is discussed and example calculations are shown for polyethylene. Effects of premelting and possibly large-amplitude motion are discovered for polyethylene in the temperature range 290 to 410 K.

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Zusammenfassung Es wurde eine Abänderung der Nernst-Lindemann Gleichung vorgeschlagen, mit deren Hilfe für feste, lineare Makromoleküle errechnete Wärmekapazitäten bei konstantem Druck (C _p ) in Wärmekapazitäten bei konstantem Volumen (C _p ) umgerechnet werden können. Zur Ableitung der molaren Konstanten A₀ in dem sich wiederholenden Teil der Gleichung wurde die variable Anzahl der erregten Schwinger bei verschiedenen Temperaturen berücksichtigt. Mit der neuen Gleichung wird es möglich, dieC _p fester Polymere für einen breiten Temperaturbereich zu errechnen. Die Konstante wurde für die festen Polymere auf Grund des ermittelten thermischen Ausdehnungsvermögens und der isothermen Kompressibilität sowie der der Literatur entnommenen Wärmekapazitätsangaben berechnet. Aus Angaben von 22 festen Polymeren wurde für A₀(neu) ein Durchschnittswert von (3,9±2,4)×10^–3 (K mol)/J erhalten. Verfügt man zur Berechnung von A₀ über keine experimentellen Werte für Kompressibilität und Ausdehnungsvermögen, so kann dieser durchscnittswert als universale Konstante angewendet werden. Die verbleibende Temperaturabhängigkeit von A₀(neu) wird besprochen und Beispielrechnungen für Polyäthylen gegeben. Für Polyäthylen wurden im Temperaturbereich 290 bis 410 K Effekte durch Vorschmelzen und Bewegungen mit großer Amplitude festgestellt.

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-, (C _p ) (C _v ) , . A ₀ , . C _p . A ₀ , , . 22 , A ₀ () (3,9±2,4)· 10^–3 ·/. A ₀ . A ₀ , . 290–410 .