Kinetic study of the oxidation of alcohols by cetyltrimethylammonium permanganate

Kinetics of the oxidation of 2-propanol, 1-butanol, 2-butanol and 1-pentanol by cetyltrimethylammonium permangenate oxidant have been investigated. The reactions are autocatalytic, colloidal manganese dioxide as one of the reaction products has been identified as the auto-catalyst.

---

2-, 1-, 2- 1- . . , , .

     

Photocatalyzed decomposition of potassium permanganate solution

A tentative mechanism is suggested for the photocatalysed decomposition of KMnO₄ solution. The catalytic activity could not be correlated with the catalysts' band gap. First order kinetics was observed using ZnO catalyst. The effects of the mass of ZnO and of different treatments of rutile are reported.

---

KMnO₄. . ZnO . ZnO .

     

Nature of intermediates in the synthesis of hydrocarbons from methanol

According to the GC-MS analysis of the composition of liquid hydrocarbons obtained in methanol conversion on ZSM-5 zeolites and the selectivity of cyclohexene conversion on these catalysts, the sequence of the aromatization reaction steps is discussed.

---

-- , ZSM-5, .

     

Toluene steam dealkylation over Rh/Al2O3. Effect of the support

Rh catalysts supported on different -aluminas were prepared and tested under identical conditions. Both catalytic activity and selectivity seem to depend on the surface concentration of acid sites. The bifunctional character of the catalyst and the role played by the support in activating the reactants are confirmed.

---

, - . , . , .

     

Oxidizing properties of alumina towards alcohols. Possible reaction scheme

By chemical trapping, an acyl species has been evidenced in the oxidation of alcohols to carboxylate on an alumina surface. A possible reacton scheme is discussed.

---

. .

     

Differential thermal analysis study of various oxalates in oxygen and nitrogen

Differential thermal analysis (DTA) of some 25 oxalates are reported in atmospheres of oxygen and nitrogen. It is shown that in some cases in nitrogen the metal is formed, in other cases the oxide of lowest valency state is produced, while a third group give the same oxide product in nitrogen and oxygen. The production in oxygen of the oxide for the first group, and of a higher oxide in the second group is a phenomenon which in the first case involves a further reaction of the metal with the oxygen atmosphere. Another group of oxalates produce characteristic DTA curves due to the formation of carbonate as the initial decomposition product. The dehydrations of these oxalates are marked by endothermic peaks.

---

Zusammenfassung Es wurden 25 verschiedene Oxalate durch DTA in Stickstoff- und Sauerstoffatmosphäre untersucht. In einigen Fällen wurde in Stickstoff das Metall gebildet, in anderen das Oxyd von niedrigster Wertigkeit. Es kommt auch vor, daß das gleiche Produkt in beiden Gasen entsteht. Beide erwähnten Produkte werden in Sauerstoff entsprechend oxydiert. Bei einigen Oxalaten erhielt man charakteristische Spitzen, die zeigten, daß das erste Zersetzungsprodukt Karbonat war. Die Dehydration dieser Oxalate zeigte sich durch endothermische Spitzen.

---

Résumé On communique les résultats de l'étude de 25 oxalates par analyse thermique différentielle, dans l'oxygène et dans l'azote. On montre que pour certains d'entre eux, dans l'azote, le métal se forme, et que pour d'autres l'oxyde correspondant à la valence la plus faible apparaît; d'autres encore donnent le même oxyde dans l'azote et dans l'oxygène. Dans l'oxygène, et pour le premier groupe, il se forme l'oxyde, tandis que l'oxyde supérieur apparaît pour le second groupe; dans le premier cas, une réaction ultérieure du métal avec l'oxygène de l'atmosphère est mise en jeu. Un autre groupe d'oxalates donne des enregistrements d'ATD caractéristiques en raison de la formation de carbonate comme produit de décomposition initial. Ces oxalates se déshydratent en donnant des pics endothermiques.

---

() 25 . , , , . , , , , , , . , , . .

     

Reactions of isoflavone and 2-hydroxyisoflavanone with sodium ethoxide in anhydrous ethanol

Recent observation /1,4/ on the existence and unreactivity of IV under basic conditions, as well as its part in the inhibitory effect on the decomposition into deoxybenzoin is unequivocally proved by comparing the decompositions of I and VI. It is also shown that the decomposition of I is detemined neither by the character of the solvent nor by the nucleophilic character of the reactant, but by the possibility of the formation of IV.

---

IV , I VI. , I . , , IV.

     

Kinetic dependences foro-xylene oxidation to phthalic anhydride over V?Ti?O catalysts

In accordance with structural data and numerical analysis of relaxation curves, a detailed scheme for the reaction of o-xylene oxidation is suggested.

---

-.

     

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.

---

, 3% Ir–Fe/Al₂O₃ . , , .

     

Characterization and thermoanalytical investigations of silver tellurite

Silver tellurite, prepared by precipitation, crystallized in tetragonal form and DSC studies show that it undergoes phase transformations on heat-treatment in the temperatuae ranges 578–604 K and 695–717 K. X-ray diffractometry suggests that in the first transformation, which is irreversible, the tellurite transforms to monoclinic form. The second transformation is reversible and the high temperature phase reverts back to the monoclinic form on cooling. The reversible phase transformation could be ascertained by electrical resistivity and reflectance spectrum measurements. The kinetic parameters, computed from the DSC data, show that the energy of activation, entropy of activation and the frequency factor are high. This is attributed to the effectiveness of a large number of vibrations.

---

Zusammenfassung Durch Ausfällen hergestelltes Silbertellurit kristallisiert tetragonal und DSC-Untersuchungen zeigen, daß es bei Einwirken von Wärme in den Temperaturbereichen 578–604 K und 695–717 K Phasenumwandlungen vollzieht. Röntgendiffraktometrische Untersuchungen lassen vermuten, daß sich das Tellurit bei der ersten Phasenumwandlung, die eine irreversible ist, in die monokline Form umwandelt. Die zweite Umwandlung ist umkehrbar und die Phase bei höherer Temperatur wandelt sich bei Abkühlen wieder in die monokline Form um. Die reversible Phasenumwandlung konnte mittels Messung des elektrischen Widerstandes und durch Aufnahme des Reflexionsspektrums festgestellt werden. Die aus den DSC-Daten berechneten kinetischen Parameter zeigen eine hohe Aktivierungsenergie, eine hohe Aktivierungsentropie und einen großen Frequenzfaktor. Dies wird der Wirksamkeit der großen Anzahl an Schwingungen zugeschrieben.

---

, 578–604 695–717 . , , . 712 . . . , , , .

---

---

The authors are thankful to the University Grants Commission, New Delhi for the financial assistance. Thanks are also due to Professor K. N. Goswami for help in computer programming.     

Effect of Ga on catalytic behavior of Pt catalyst

Platinum-gallium/alumina supported catalysts have been studied. With gallium loadings increasing, the catalysts show very different catalytic performance in n-hexane conversion due to gallium effect on the bifunctionality.

---

-, . -, .

     

IR study of adsorbed piperidine dehydrogenation on oxidic or sulfided Ni?W/Al2O3 catalysts

IR spectroscopy has been used to follow the transformation at different temperatures of piperidine chemisorbed on oxidic or sulfided Ni–W/Al₂O₃ catalysts. Formation of an intermediate species, possibly tetrahydropyridine, and pyridine is evidenced. Their formation temperature on the sulfided samples accounts for the catalyst activity in pyridine hydrogenation under H₂ pressure.

---

- , Ni–W/Al₂O₃, . , , . .

---

---

This work was supported by the Groupement scientifique Hydrotraitement catalytique (CNRS-IFP, TOTAL. ELF).     

Kinetics of catalyst regeneration by coke combustion. II. Influence of temperature rise in the catalyst particles

A grain-pellet model has been used to study the effect of high reaction rates upon the temperature profiles developed during regeneration of coked catalyst particles. The possibility of falsification of kinetic data is discussed in view of the results obtained.

---

- , . .

     

Kinetics of propylene oxidation to acrolein on an Fe?Sb oxide catalyst

The kinetics of propylene oxidation to acrolein and CO₂ on a Fe–Sb oxide catalyst have been studied in an integral reactor. A satisfactory rate equation has been derived with the assumption of a linear dependence of the activation energy and heats of adsorption of oxygen and water on the degree of reduction of the catalyst.

---

CO₂ Fe–Sb . , .

     

Transalkylation of phenols over heteropoly acids

Transalkylation of 2,6-di-tert-butyl-4-R-phenols over solid heteropoly acids (H₃PW₁₂O₄₀, H₄SiW₁₂O₄₀, H₃PW₁₂O₄₀/SiO₂, H₄SiW₁₂O₄₀/SiO₂) in the presence of toluene or o-xylene as acceptors of a tert-butyl group at 100–140 °C produces 4-R-phenols with 92–98% yield (R = H, alkyl, aryl, etc.). HPAs are effective catalysts for the transalkylation of p-cresol and 2, 6-ditert-butyl-4-methylphenol.

---

2,6----4-R- (H₃PW₁₂O₄₀, H₄SiW₁₂O₄₀, H₃PW₁₂O₄₀/SiO₂, H₄SiW₁₂O₄₀/SiO₂) 0- - 100–140°C 4-R- 92–98% (R = H, , ..). - 2,6----4-.

     

Kinetics of charge transfer complex formation with alicyclic n-donors

Kinetic investigations on the formation of charge transfer complexes with three alicyclic n-donors (piperidine, piperazine and morpholine) in chloroform, using chloranil and bromanil as acceptors, have been carried out spectrophotometrically. A mechanism consiestent with the experimental results is proposed. Activation parameters evaluated are in correlation with the pKa values of the donors.

---

- (, ) , , . , . .

     

Influence of lanthanum on K/Fe/silicalite-2 catalyst in CO+H2

The promotion of a K/Fe/silicalite-2 catalyst with lanthanum increases the selectivity of C₂–C₄ olefin and conversion of carbon monoxide. The influence of lanthanum on the catalyst has been characterized by TPR, TPD and XPS techniques. The suitable lanthanum content in the chemical composition of the catalyst is determined.

---

K/Fe/-2 C₂–C₄ . , . .

     

Kinetics of reduction of an iron catalyst for ammonia synthesis

The kinetics of reduction of an iron catalyst have been studied at 450–550 °C. The overall kinetic equation was of the mixed-control type. The equation of the surface reaction was of the Langmuir-Hinshelwood type with the adsorption of only water vapor taken into account.

---

450–550°C. . - .

     

Mechanism of thermal decomposition of lead thiosulphate

The thermal decomposition of lead thiosulfate (LTS) was studied by various methods: X-ray phase analysis, IR and ESR spectroscopy, etc. A mechanism of thermal decomposition is suggested, including rupture of the S-S bond and the formation of radicals. According to the mechanism, the reaction rate can be enhanced in the presence of the PbS phase. The formation of PbS is the cause of the topochemical character of the reaction. The composition of the thermolysis products of LTS containing a radioactive isotope of sulfur is predicted.

---

Zusammenfassung Die thermische Zersetzung von Bleithiosulfat PbS₂O₃ wurde durch Röntgenphasenanalyse, IR- und ESR-Spektroskopie und Thermogravimetrie untersucht. Ein Mechanismus der thermischen Zersetzung wird angegeben, der über die Trennung von S-S-Bindungen und die Bildung von Radikalen verläuft. Nach diesem Mechanismus wird die Reaktionsgeschwindigkeit in Gegenwart der PbS-Phase beschleunigt, was den topochemischen Charakter der Reaktion bedingt.Für die Verteilung radioaktiven Schwefels auf die Zersetzungsprodukte unterschiedlich markierten (PbS^*SO₃ bzw. PbSS^*O₃) Bleithiosulfats wird eine Vorhersage gemacht.

---

, - . , S—S . , . . , .

     

On the problem of predicting the activity of oxide and carbonate catalysts in some reactions of petrochemical synthesis

The problem of predicting the activity of oxide and carbonate catalysts for some reactions of petrochemical synthesis (vapor phase conversion of carboxylic acids, catalytic oxidation of asphaltic tar to bitumen) according to the established dependence of thermal stability variations of intermediates on the formation enthalpy of metal oxides or standard ele.trode potentials is discussed.

---

, ( , ) .