Response studies of the mechanism of o-xylene oxidation over a vanadium-titanium oxide catalyst

A response method has been used to study the mechanism of o-xylene oxidation over a vanadium-titanium oxide catalyst. The products of partial and destructive oxidation are shown to be formed under the influence of molecular oxygen on the surface intermediates produced by the interaction between o-xylene and oxidized surface sites.

---

- . , , - .

     

Decomposition of cumene hydroperoxide in the presence of metal 1,2-dithiolate complexes

Metal 1,2-dithiolate complexes were studied as catalysts for decomposition of cumene hydroperoxide. Reaction proceeds by a two-stage process and the first stage, corresponding to destruction of the metal complex, is influenced by the type of metal and substituents on the dithiolate ligand. On average, almost two sulfur atoms in each metal chelate are oxidized to SO₂ or SO₃, which decompose the main part of hydroperoxide.

---

1,2- . : . SO₂ SO₃, .

     

Textural changes in alumina coked by toluene cracking in fluidized bed

The texture of an alumina coked at 873–923 K has been studied by specific area measurements and determination of pore size distributions. Two opposite textural changes have been observed: a strong plugging of the microporosity (r=18–30 Å) and an increase of the porous volume and surface area of the larger porosity (r=30–1000 Å).

---

, 873–923 , . : (r=18–30 Å) (r=30–100 Å).

     

Interaction of super-finely dispersed Al powders with water

Interaction of super-finely dispersed Al powders (SFDP) with water is characterized by the presence of a considerable section on the kinetic curves, where the conversion rate is maximum and its degree is as high as =0.5–0.7. It is suggested that the essential factor accounting for the conversion kinetics and the phase composition of its products is the self-heating of Al particles.

---

() , , () 0,5–0,7. , .

     

Reactions of C4?C6 alkanes on platinum and platium-gold films

Results are reported on the reactions of n-butane, n-pentane and n-hexane on Pt and Pt/Au alloy films. The results are compared with those obtained for Pt–Au alloys on a SiO₂ carrier. It is concluded that alloying can change the selectivity of the catalyst. No indication has been found for the possible role of oxygen in the high selectivity of Pt in non-destructive reactions.

---

-, - - Pt . , Pt–Au SiO₂. , . - Pt .

     

Decomposition of ammonia on rhenium I. Hydrogen adsorption on rhenium

Field emission microscopy and thermal desorption studies of hydrogen adosrption on a monocrystal tip and a polycrystalline rhenium wire indicate dissociative adsorption which proceeds with an initial sticking coefficient of S_o0.2 and an isosteric adsorption heat of about 138 kJ/mol.

---

. , , S_o0.2 138 /.

     

Active component of vanadium catalysts in oxidation of gases with low concentrations of SO2

EPR and NMR studies show that in oxidation of gases with low concentrations of SO₂ the molten active component of K/V and Cs/V catalysts becomes inhomogeneous and contains V⁵⁺ compounds having different activities.

---

, SO₂ K/V Cs/V , V⁵⁺.

     

Photocatalytic electron transfer across the membranes of lipid vesicles mediated by diglycylamide of mesoporphyrin-IX N-metylglycomate

A peculiarity of the photocatalytic action of porphyrin molecules with different localization inside lipid bilayers of lecithin vesicles has been studied. The influence of an electrostatic field in the lipid membrane on the efficiency of electron photocatalytic transfer across the membrane is discussed.

---

, - . . .

     

Effect of specific and nonspecific interactions on deutero-protium exchange in solution

The effect of electrostatic type interactions on the deutero-protium heteroexchange of dihydrogen with solutions catalyzed by bases, with the decisive role of hydrogen bonds and particularly of the H-bonds having increased strength, is discussed.

---

- .

     

Characterization of the interaction of CO and H2 at the ZnO surface by adsorption microcalorimetry

CO and H₂ are both chemisorbed by ZnO but H₂ is more sensitive than CO to the surroundings of adsorption sites. When the two gases are coadsorbed, a strong interaction occurs, ascribed to the formation of a possible precursor in methanol synthesis.

---

CO H₂ ZnO, H₂ , , CO. , , .

     

Effect of the medium on the oxidation of aliphatic monocarboxylic acids

Oxidation rates and k₂/k₆ ratios are given for some acids from propionic to lauric. The k₂/k₆ ratio is shown to be influenced by the electrostatic effect of the solvent. A linear dependence between the isodielectric values of k₂/k₆ and the number of methylene groups in the acid molecules is described.

---

k₂/k₆ . k₂/k₆ k₂/k₆ .

     

Differential thermal analysis of the phase transition of dicalcium orthosilicate Ca2SiO4 under a reducing atmosphere

The transformation of Ca₂SiO₄ was investigated with regard to the disintegration of the sinter in alumina manufacturing. DTA was applied to study the effect of the reducing atmosphere upon the course of the polymorphic transitions of Ca₂SiO₄, and particularly the self-disintegration process. Pure synthetic dicalcium orthosilicate and blends of pure components from the system CaO-Al₂O₃-SiO₂-Fe₂O₃ were compared with technological mixtures of limestone and fly ash. Data obtained from the DTA runs allowed the specification of technical parameter for both firing and cooling of the sinter.

---

Zusammenfassung Die -Umwandlung in Ca₂SiO₄ wurde im Hinblick auf den Zerfall von Sinter in der Tonerdeproduktion untersucht. Mittels DTA wurde der Einfluß einer reduzierenden Atmosphäre auf den Verlauf der polymorphen Umwandlungen von Ca₂SiO₄ und insbesondere auf den Zerrieselungsprozeß verfolgt. Reines synthetisches Ca₂SiO₄ und Gemische reiner Komponenten des Systems CaO-Al₂O₃-SiO₂-Fe₂O₃ wurden mit technischen Mischungen aus Kalk und Flugasche verglichen. Die Ergebnisse von DTA-Versuchen erlauben die Spezifizierung der technischen Bedingungen für das Brennen und Abkühlen des Sinters.

---

. , , . -l₂₃-SiO₂-F23 . .

     

Recent progress in titration calorimetry

Research developments in titration calorimetry over the past ten years by personnel at the Thermochemical Institute have resulted in new techniques and instrumentation that have greatly increased the usefulness of calorimetry in the study of chemical problems. During this time, problems associated with the components of the calorimeter (i.e., constant temperature bath, constant rate buret, reaction vessel, temperature sensing circuit, and data analysis procedure) have been solved so that the continuous titration method now gives results comparable in accuracy to those obtained with conventional solution calorimeters. These developments have opened new avenues of research in the fields of biochemistry, microbiology, and environmental analysis.

---

Zusammenfassung Die Fortschritte der Forschung auf dem Gebiete der Titrationskalorimetrie, welche in den vergangenen Jahren von Mitarbeitern des Thermochemischen Instituts erreicht worden sind, führten zu neuen Techniken und neuer Instrumentation, die die Einsatzfähigkeit der Kalorimetrie zur Untersuchung chemischer Probleme wesentlich erhöhten. Während dieser Zeit wurden Probleme in Zusammenhang mit den Bestandteilen des Kalorimeters (d.h. Konstanttemperaturbad, Burette mit konstanter Geschwindigkeit, Reaktionsbehälter, Temperatur, Wärmefühler-Stromkreis und Datenverarbeitungsvorgang) gelöst, so daß die kontinuierliche Titrationsmethode jetzt Ergebnisse von einer Genauigkeit liefert, welche mit der in herkömmlichen Lösungskalorimetern erhaltenen vergleichbar ist. Diese Entwicklungsarbeit eröffnet neue Wege der Forschung auf den Gebieten der Biochemie, Mikrobiologie und Umweltschutzanalyse

---

Résumé Les recherches effectuées durant les dix dernières années par le personnel de l'Institut de Thermochimie ont eu pour résultat la mise au point d'appareils nouveaux qui augmentent, considérablement l'applicabilité de la calorimétrie à l'étude des problèmes chimiques. Ainsi les problèmes associés aux composants d'un calorimètre (c'est-à-dire bain à température constante, burette à vitesse constante, récipient réactionnel, circuit détecteur de température et procédés d'analyse des données) ont été résolus. C'est pourquoi la technique du titrage en continu donne maintenant des résultats d'une exactitude comparable à celle obtenue avec les calorimètres en solutions conventionnels. Ces développements ont ouvert de nouvelles perspectives de recherche dans les domaines de la biochimie, de la microbiologie et des analyses liées à la protection de l'environnement.

---

, , , . , : , , , - . , , , . , .

     

Thermal stabilities of copolymers of styrene and acrylic acid and their salts

The thermal stabilities of copolymers of styrene and acrylic acid and their alkali metal salts have studied.The thermal stability properties T_i and T_s, and the kinetic parametersn, E, S andZ were determined and the results are discussed. It was found that the thermal stabilities of the investigated copolymers of styrene and acrylic acid are somewhat lower than that of polystyrene and decrease with increase of the quantity of acrylic acid introduced into the copolymers.The thermal stabilities of the sodium salts of these copolymers are somewhat higher than those of the initial copolymers, and are almost equal to that of polystyrene.The thermal stabilities of the investigated ionomers depend on the nature of the alkali metal introduced into the copolymer.

---

Zusammenfassung Es wurde die thermische Stabilität von Kopolymeren aus Styrol und Acrylsäure bzw. Acrylsäurealkalimetallsalzen untersucht. Die Werte T_i und T_s für die thermische Stabilität sowie die kinetischen Parametern, E,S undZ wurden bestimmt und die Ergebnisse diskutiert. Man fand, daß die thermische Stabilität der untersuchten Kopolymere aus Styrol und Acrylsäure etwas niedriger ist als die von Polystyrol und daß sie mit einer Zunahme des Anteiles an Acrylsäure an den Kopolymeren absinkt. Die thermische Stabilität der Natriumsalze dieser Kopolymere erwies sich als etwas höher als die die ursprünglichen Kopolymere, erreicht aber nur die von Polystyrol. Die thermische Stabilität der untersuchten Ionomere hängt von der Art der in die Kopolymere eingebrachten Alkalimetalle ab.

---

. T _i ,T _s , E, n, S Z. , , . , , . , .

     

Synthesis and thermal stability of the adducts of rare earth element β-diketonates with macrocyclic polyethers

Synthesis methods for the adducts of lanthanoid pivaloyltrifluoroacetonates with 1,4,7,10,13,16-hexaoxacyclooctadecane are described. The applicability of thermal analysis at quasi-equilibrium conditions for coordination compounds of this type is demonstrated for the first time. Based on experimental results the effect of the starting reactants on the structure of the adducts, on their volatility and thermal stability is established.

---

Zusammenfassung Methoden zur Synthese von Addukten von Lanthanoidpivaloyltrifluoracetonaten mit 1,4,7,10,13,16-Hexaoxacyclooctadekan werden beschrieben. Die Anwendbarkeit der thermischen Analyse unter Quasi-Gleichgewichtsbedingungen zur Untersuchung von Koordinationsverbindungen wird erstmals aufgezeigt. Basierend auf die Versuchsergebnisse wird die Beziehung zwischen der Natur der Reaktanten und der Struktur, der Flüchtigkeit und der thermischen Stabilität der Addukte aufgezeigt.

---

1,4,7,10,13,16- . , .

     

The thermoanalytical determination of deactivation types of cation-exchanger catalyst's

The dependence of the thermal decomposition of a cation-exchanger catalyst on its deactivation type has been ascertained, and thermal analysis has been suggested as a diagnostic method for the determination of the condition of such a catalyst.

---

Zusammenfassung Die Abhängigkeit der thermischen Zersetzung eines Kationaustauscher-Katalysators von seinem Inaktivierungstyp wurde bewiesen und die Thermoanalyse als diagnostische Methods für die Bestimmung des Zustandes eines solchen Katalysators vorgeschlagen.

---

. , .

     

“In situ” EPR studies of interaction between benzene and ZSM-5 zeolites

The effect of the state of adsorbed layers on the formation of monomeric and dimeric benzene cation-radicals (CR) on ZSM-5 zeolites has been studied. Removal of benzene is shown to be accompanied by disappearance of CR, which is reversible and takes place with preservation of the sites for their stabilization.

---

- (KP) ZSM-5. , KP, .

     

Observations on the acetone-malonic acid mixed substrate hydrogen peroxide-iodate-manganese(II) oscillating system

The acetone-malonic acid mixed substrate hydrogen peroxide-iodate-manganese(II) oscillating system has been examined under fixed conditions where two oscillatory phases are separated by a lengthy iodine production and consumption period. The intermediate period is considered to result from oxidation of malonic acid-iodomalonic acid.

---

- — — (II) , . - .

     

Mechanism of action of sulfur-containing complexes in oxidation processes

A mechanism of the inhibiting action of Cu(II), Ni(II), Pb(II), Zn bis(N, N-dialkyldithiocarbamates) and Cu(II) bis (-thiopicolineanilides) in the AIBN initiated oxidation of ethylbenzene, styrene and nonene-1 is proposed. Inhibition is due to the deactivation of free radicals upon interaction with the chelate active center consisting of a metal with coordinated ligand atoms. As supported by the experimental data, the reaction occurs by an electron transfer mechanism.

---

-(N,N-) Cu(II), Ni(II), Pb(II), Zn -(-) Cu(II) , -1. . . .

     

Selective formation of propylene by acid-base catalyzed conversion of methyl alcohol over MgZSM-5

A reaction scheme for propylene formation from methyl alcohol over ZSM-5-based catalysts is proposed which involves two vicinal acidic-basic sites.

---

ZSM-5. - - .