Cyclohexanol conversion of Pt-and Co-promoted molybdena-alumina; Effect of S-uptake

The uptake of sulfur reduces the overall activity of PtMo/Al₂O₃ and enhances that of CoMo/Al₂O₃ in conversion of cyclohexanol. Significant changes in selectivity indicate the existence of different active sites of the initial catalyst for hydro-dehydrogenation and dehydration. The differences in catalytic activity expressed in terms of overall TOF decrease with increasing sulfur treatment like for Ru and Ir promoted catalysts.

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PtMo/Al₂O₃ CoMo/Al₂O₃. - . Ru .

     

Combination and disproportionation of methyl and 2-propyl radicals with 1,1,2-trimethylallyl radicals

The combinations and disproportionations of the CH₃ and 2-propyl (iP) radicals with the 1,1,2-trimethylallyl (TMA) radical have been studied in the gas phase in the temperature interval of 389–451 K and 490–540 K, respectively. For the ratios of the terminal (t) and non-terminal (n) combinations of the CH₃ and iP radicals with the TMA radical, values of 1.9±0.1 and 2.84±±0.10 were obtained, respectively. The ratios of the tt and tn and nn to tn combinations of the TMA radical were 1.59 and 0.46, respectively. The disproportionation-combination rations were (CH₃ , TMA)=0.022±±0.012 and (iP, TMA)=0.026±0.011.

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CH ₃ 2- (iP) 1,1,2- (TMA) : 389–451 K 490–540 K. (t) (n) TMA 1,9±0,1 2,84±0,10, . tt tn nn tn TMA 1,59 0,46, . (CH ₃ , TMA)=0,022±0,012 (iP, TMA)=0,026±0,011.

     

Structure and reactivity of vanadium-phosphorus oxides

The contribution of thermal methods of analysis to the study of the structure and reactivity of vanadium-phosphorus oxides is examined. In particular, data are reported on the solid-state reaction VOHPO₄·1/2H₂O(VO)₂P₂O₇+2 H₂O for VOHPO₄·1/2H₂O prepared in different ways, on the redox properties of oxidation and reduction of vanadium for catalysts prepared with different PV atomic ratios in the range 0.9–1.3, and on the surface properties determined by TPD of catalysts with different PV ratios. The relationship between these properties and the catalytic properties in the selective oxidation ofn-butane and but-1-ene is discussed.

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Zusammenfassung Der Beitrag thermischer Analysenmethoden zur Untersuchung der Struktur und Reaktivität von Vanadin-Phosphor-Oxiden wird erörtert. Insbesondere werden sich auf die Festkörperreaktion 2VOHPO₄.1/2H₂O(VO)₂P₂O₇+2H₂O für auf verschiedene Weise dargestelltes VOHPO₄.1/2H₂O, auf die Redox-Eigenschaften von Vanadin in Katalysatoren mit P/V-Atomverhältnissen im Bereich 0.9–1.3 und auf durch TPD bestimmte Oberflächeneigenschaften von Katalysatoren mit unterschiedlichen P/V-Verhältnissen beziehende Angaben gemacht. Zusammenhänge zwischen diesen Eigenschaften und den katalytischen Eigenschaften bei der selektiven Oxydation von n-Butan und N-Buten werden diskutiert.

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- . , VOHPO₄ · 1/2H₂O, VOHPO₄ · 1/2H₂O(VO)₂P₂O₇ + 2H₂O, - PV 0,91,3. - 1-.

     

Etude thermoanalytique de quelques steroides I — Monovalerianate d'estradiol et estriol

A thermoanalytical study of estradiol monovalerate (a) and estriol (b) revealed the thermal stability, the decomposition kinetics, and the temperatures and intervals of fusion. The degree of purity was calculated only for estradiol monovalerate: 99.72 ± 0.11 mol %. The fusion enthalpy (29.45±0.47 kJ mol^–1) and entropy for this compound were evaluated by differential scanning calorimetry. It was also possible to detect the polymorphism and the pseudopolymorphism of (a) and (b) after recrystallization from several solvents.

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Zusammenfassung Die thermische Stabilität, die Zersetzungskinetik sowie die Schmeiztemperaturen und -intervalle von Estradiol-Monovalerianat (a) und Estriol (b) wurden thermoanalytisch ermittelt. Nur der Reinheitsgrad von (a) wurde berechnet (99,72 ± 0,11 mol %). Die Schmelzenthalpie (29,45±0,47 kJ · mol^–1) und Schmelzentropie dieser Verbindung wurden mittels DSC bestimmt. Nach Rekristallisation in verschiedenen Lösungsmitteln konnten Polymorphie und Pseudopolymorphie für (a) und (b) nachgewiesen werden.

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, . 99,72±0,11 %. (29,45±0,47 · ^–1) . , .

     

Physico-chemical transformations during heating of phosphorites

The thermal behaviour of phosphorites in an oxygen or helium atmosphere was studied by means of simultaneous TG-DTG-DTA-gas titrimetric EGA. Thermal oxidation and/or decomposition steps of the contaminating organic materials, carbonate minerals and pyrite, and of the fluorocarbonate-apatite were identified. The evolution of CO₂ from the latter has its maximum at 750–850 °C and is accompanied by an increase in the lattice parametera ₀.

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Zusammenfassung Das thermische Verhalten von Phosphoriten in Sauerstoff- oder Heliumatmosphäre wurde durch simultane TG-DTG-DTA-EGA (mittels Gastitrimetrie) untersucht. Thermische Oxidations- und/oder Zersetzungsschritte der Verunreinigungen (organische Materialien, Carbonatminerale und Pyrit) und des Calcium-fluoro-carbonat-apatit wurden identifziert. Die CO₂-Abspaltung aus dem letzteren hat ihr Maximum bei 750–850 °C, sie ist begleitet von einer Vergrösserung des Gitterparametersa ₀.

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, , - . ( , , . 750–850° ₀.

     

Kinetics of CO2 formation in thermal destruction of brown coals

The previously suggested approach to the problem of kinetic system identification /1/ was used for the system of independent first order reactions. The analysis of the curves of CO₂ formation in thermal destruction of brown coal indicates that both structure and model parameters of real processs can be identified in terms of the continuity concepts.

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(I) ë . CO₂ , , .

     

Evaluation of quantum yields in the presence of an absorbing additive

A method is proposed for the evaluation of quantum yields of photochemical reactions studied in the presence of absorbing additives using cylindrical sample tubes.

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.

     

Preparation and characterization of Ru?Pb supported catalysts

Decomposition of Mn₃Mo₂TeO₁₂ during oxidation of toluene to benzaldehyde was observed. Depending on the surface composition of the initial catalyst, the decomposition leads to less active but highly selective MnMoTeO₆ or to MnMoO₄ which is not selective in toluene oxidation.

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Mn₃Mo₂TeO₁₂ . , MnMoTeO₆, MnMoO₆.

     

Oxidative elongation of lower paraffins

It is shown that the oxidative condensation of ethane on CoMo/-Al₂O₃ catalysts is in principle possible. The conceivable paths of this reaction are analyzed.

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- .

     

Catalytic reaction of methane with carbon dioxide

High activities and selectivities of Ni on SiO₂ catalysts producing CO in the reaction of CH₄ with CO₂, have been obtained at relatively low temperatures. These aspects are considerably different from the activities or selectivities of other catalysts, and have been explained by assuming that the Ni on SiO₂ catalyst markedly suppresses carbon deposition.

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CO Ni SiO₂ CH₄ CO₂. , Ni SiO₂.