Oxidative coupling of 5-membered heterocycles catalyzed by a Pd(II)-heteropolyacid system in dimethylformamide

Oxidative coupling of thiophene and 2-methylfuran to the corresponding dihetaryls in DMFA medium occurs in the presence of the homogeneous catalytic system Pd(II)-molybdovanodophosphoric heteropolyacid (HPA). The data obtained show that HPA may act as a reversible oxidant in polar aprotic media.

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, Pd(II)- 2- . , .

     

Reaction mechanism and principles of choosing catalysts for selective oxidation at C?H bonds

Reaction mechanism for selective oxidation of organic compounds at C–H bonds is discussed. The criteria of selecting catalysts for these reactions have been formulated; 1) fast heterolytic activation of C–H bonds; 2) relatively slow primary activation of oxygen; 3) fast diffusion of oxygen vacancies; 4) fast electron transfer from the adsorbed substrate to catalyst.

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C–H . : 1) C–H ; 2) ; 3) ; 4) .

     

Infrared study of the interaction of nitric oxide with CuY zeolites

Infrared studies of the interaction of NO with CuY–A zelites have been made over the temperature range from –100°C to 400°C. Several forms of NO adsorption have been found, in particular, a stable cis-dimer at low temperatures.

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- (–100+400°C) NO CuY–A . NO, ë - .

     

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.

     

Low-temperature ortho-para conversion of hydrogen on films of rare-earth metals and their copper alloys

Kinetic data for the ortho-para conversion of H₂ at 77 k rear earth metals (REM) and their Cu alloy films are given. Conversion on the surface of Sc, Y, La, Yb and Lu has been shown previously to follow a chemical mechanism, for the others it is magnetic. When alloyed with Cu, the specific catalytic activity (K_sp) of Sc, Y, La, Yb and Lu sharply increases. A sharp increase of K_sp is also observed on Cu alloys of Ce, Sm, Nd, Pr, Eu and Gd and the chemical conversion mechanism becomes predominant. On Tb, Dy, Er, Ho and Tm, K_sp rises only slightly and the magnetic mechanism preserves.

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- H₂ 77 P3M . , Sc, Y, La, Yb Lu , . Cu () Sc, Y, La, Yb, Lu, Ce, Sm, Nd, Pr, Eu Gd, . Ha Tb, Dy, Er, Ho Tm .

     

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.

     

Ein Beitrag zur thermischen Stabilität der Clathratverbindungen der Doppelcyanide in Abhängigkeit von ihrer Struktur

Zusammenfassung Die thermische Zersetzung zweier Hofmann'scher Clathratverbindungen, sowie der Verbindung Cd(NH₃)₂Hg(CN)₄·2 C₆H₆ wurde mittels des Derivatographen untersucht. Diese Clathratverbindungen sind bezüglich ihrer Struktur verschieden. Die Clathrate des Hofmann'schen Typs sind von höherer Stabilität. Die Gründe hierfür werden erörtert.

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The thermal decompositions of two Hofmann's clathrate compounds and the compound Cd(NH₃)₂Hg(CN)₄ · 2 C₆H₆ have been investigated by means of the derivatograph. These clathrate compounds are, as for their structure, different. Clathrate of the Hofmann's types represent the higher stability. The reasons are discussed in this paper.

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Résumé On a étudié, à l'aide d'un Derivatograph, la décomposition thermique de deux clathrates de type Hofmann ainsi que du composé Cd(NH₃)₂Hg(CN)₄·2 C₆H₆. Les clathrates étudiés possèdent des structures différentes. Les clathrates de type Hofmann sont les plus stables. Les raisons en sont discutées dans la présente communication.

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, 1,3,5,7--1,3,5,7- (), 1,5--3,7--1,3,5,7- (DADN), 1,5--3,7- -1,3,5,7- (D), 1,3,5--1,3,5- (-) 1,5--3,7- -1,3,5,7- (DNPT). , , DADN RDX . , R- DNPT, , . DPT.

     

Kinetics of thermal decomposition of MCO3 to MO (M=Ca,Sr and Ba)

The kinetics of the thermal decompositions of CaCO₃, SrCO₃ and BaCO₃ into their oxides were studied by thermogravimetry at constant and linearly increasing temperatures. The kinetics of the isothermal decompositions of calcium and strontium carbonates were described by the lawR _n =1–(1–)^1/n , wheren=1.8 and 1.2, respectively. The kinetics of the non-isothermal decompositions of the two carbonates, analysed by the Ozawa and Coats-Redfern methods, were in keeping with the isothermal kinetics. True kinetic compensation laws were established for each decomposition of the two carbonates, including the data under both isothermal and non-isothermal conditions.As concerns the decompositions of BaCO₃, however, there was some difference between the kinetic features relating the isothermal and non-isothermal conditions. A true kinetic compensation law was not established in this case.

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Zusammenfassung Die Kinetik der thermischen Zersetzung von CaCO₃, SrCO₃ und BaCO₃ zu den Oxiden wurden durch Thermogravimetrie bei konstanter und linear ansteigender Temperatur untersucht. Die Kinetik der isothermen Zersetzung von Calcium- und Strontium-carbonat folgt dem GesetzR _n =1–(1 –)^1/n, won=1,8 bzw. 1,2. Die Kinetik der nichtisothermen nach den Methoden von Ozawa und Coats-Redfern analysierten Zersetzung der zwei Carbonate ist in Übereinstimmung mit der isothermen Zersetzung. Wahre kinetische Kompensationsgesetze wurden für die Zersetzung der beiden Carbonate erhalten, einschließlich der sich sowohl auf isotherme als auch auf nichtisotherme Bedingungen beziehenden Daten. Was die Zersetzung von Bariumcarbonat betrifft, so wurden einige Unterschiede im kinetischen Verhalten bei der Zersetzung unter isothermen und nichtisothermen Bedingungen festgestellt. Ein wahres kinetisches Kompensationsgesetz konnte in diesem Falle nicht ermittelt werden.

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, . R _n =1–(1–)^1/n , , , 1,8 1,2. , -, . « » , . , , . - «» .

     

Dehydroxylation and catalytic activity of dealuminated Y zeolites

Dehydroxylation and catalytic conversion of m-xylene over dealuminated zeolites were studied.

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- .

     

Acetylene adsorption on a clean iridium surface

The interaction of C₂H₂ with a polycrystalline iridium surface at 140 KT500 K has been studied by AES, XPS and UPS. A model of the bonding between C₂H₂ and Ir by the 1 orbitals of the hydrocarbon is proposed. The more pronounced energy splitting between the orbitals of acetylene during adsorption compared to that in the gas phase is ascribed to deformation of the acetylene molecule.

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C₂H₂ . 140 KT500 K AES, XPS UPS. C₂H₂ Ir 1- . - , , .

     

Studies on the catalytic oxidation of propylene on ferric molybdate

Ferric molybdate is less selective in the partial oxidation of propylene than bismuth molybdate. Its catalytic behavior is similar to that observed on other transition metal molybdates. The intrafacial nature of the reaction is established through kinetic and adsorption measurements.

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, . . .

     

The autocatalytic character of the reaction methanol to hydrocarbons over amorphous silica-alumina catalysts

Conversion of methanol to hydrocarbons was studied on an amorphous silica-alumina over the 330–420°C temperature range and contact times up to 8 h. The reaction was confirmed as autocatalytic from the results of varying both contact time and temperature.

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330–420°C 8 . , , , .

     

Reduction of NO by carbon monoxide on tin dioxide

The reduction of NO by carbon monoxide on SnO₂ has been studied in the temperature range from 90 to 450°C. The complicated temperature dependence of the reaction rate is due to the interaction of CO an CO₂ with the catalyst.

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NO SnO₂ 90–450°C. , CO CO₂ .

     

Effects of radioactivity on surfaces: I. Influence of Cr-51 on the catalytic activity of chromium catalysts

Chromium catalysts were prepared on monolith supports, some of them with radioactive Cr-51 in the surface. The dehydrogenation-hydrogenation reaction of cyclohexene was used to compare the catalytic activities of the radioactive and inactive catalysts. Differences were observed in the distribution of the main products at low temperatures and of the byproducts also at high temperatures.

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, Cr-51. - . , — , .

     

Creep compliance measurements by thermomechanical analysis—Parallel plate rheometry (TMA-PPR)

A method is described for measurement of creep compliance and apparent viscosity of thermoplastic materials above their glass transition temperatures. The method utilizes a standard thermomechanical analyzer (TMA) with minor modifications. Small samples in the shape of a flat-ended cylinder are compressed isothermally between parallel plates consisting of a special probe and the base of the sample platform. Previously derived physical relationships and experimental restraints are employed. Results are reported for a polystyrene standard and an electrophotographic toner at several temperatures. Standard time-temperature superposition techniques were used to construct creep compliance master curves for the toner. It is demonstrated that TMA is ideally suited for this type of measurement.

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Zusammenfassung Eine Methode zur Messung der Kriechnachgiebigkeit und der scheinbaren Viskosität von thermoplastischen materialien oberhalb deren Glasumwandlungstemperaturen wird beschrieben. Es wurde ein thermomechanischer Standardanalyzer (TMA) mit geringfügigen Abänderungen benutzt. Kleine Proben in Form eines Zylinders mit ebenen Enden werden zwischen einer speziellen Sonde und der Basis der Probenplatte isotherm gepreßt. Vorausgehend abgeleitete physikalische Beziehungen und experimentelle Einschränkungen werden berücksichtigt. Ergebnisse werden für einen Polystyrolstandard und einen elektrophotographischen Toner und verschiedene Temperaturen angegeben. Standard-Techniken der Zeit-Temperatur-Überlagerung werden herangezogen, um Kriechnachgiebigkeitskurven für den Toner zu konstruieren. Es wird gezeigt, daß TMA für diesen Typ von Messungen ideal geeignet ist.

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. (). , . . . — . , .

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Presented at the 7th ICTA in Kingston, Ontario, Canada.

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Its is a pleasure to acknowledge Dr. Thor Smith of IBM Research for his guidance and many helpful discussions. Mel Astrahan, an exceptional summer student, deserves credit for many of the creep compliance measurements and for the computer program.     

Influence of pore diffusion on the kinetics of catalytic oxidation of ethylene

Internal diffusion influences the kinetics of ethylene oxidation on an industrial silver catalyst at temperatures higher than 240°C. This influence is completely eliminated when the diameter of the catalyst grains is decreased by a factor of 1/2.

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, 240°C. .

     

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.

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- .

     

Gel-immobilized catalytic systems for propylene dimerization containing organophosphorus ligands

Catalytic dimerization of propylene in the presence of macromolecular nickel complexes containing organophosphorus ligands has been studied. It has been established that the substitution of alkoxy groups of phosphorus atoms in the polymeric ligands does not affect the dimer composition but permits, within certain limits, to control catalyst activity.

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, . , , .

     

Studies on the thermal decompositions of As-triazine derivatives and their compounds with metal ions

The thermal decompositions of the new complex salts of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) with 5,6-diethoxyearbonylmethyl-3-seleno-1,2,4-triazine (HSeTEK) and 5,6-diethoxycarbonylmethyl-3-thio-1,2,4-triazine (HTTEK) were investigated on the basis of the respective thermal curves. The thermoanalytical investigations indicate that HSeTEK, HTTEK, and their complexes with metal ions all undergo three-stage changes as the temperature is raised. The stages of pyrolysis established from the thermal data were compared, and the rates and stages of pyrolysis were related to the structures of the compounds.

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Zusammenfassung Die thermische Zersetzung der neuen Komplexsalze von Mn(II), Co(II), Ni(II) und Cu(II) mit 5,6-Diäthoxycarbonylmethyl-3-seleno-1,2,4-triazin (HSeTEK) und 5,6-Diäthoxycarbonylmethyl-3-thio-1,2,4-triazin (HTTEK) wurden auf der Grundlage der entsprechenden thermischen Kurven untersucht. Die thermoanalytischen Untersuchungen zeigen, daß HSeTEK, HTTEK und deren mit Metallionen gebildeten Komplexe bei Temperaturerhöhung einer jeweils dreistufigen Umwandlung unterliegen. Die auf der Basis der thermischen Daten festgestellten Pyrolysestufen wurden verglichen und Geschwindigkeit und Abschnitte der Pyrolyse mittels der Struktur der Verbindungen erläutert.

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, , 5,6- -3--1,2,4- 5,6 5,6 -3--1,2,4-. , . . - .

     

IR and thermal studies on lithium oxomolybdenum(VI) oxalate

A new molybdenum(VI) complex, Li₂[Mo₂O₆(C₂O₄)] · 2 H₂O (LMO), was prepared and characterized by chemical analysis and IR spectral studies. Its thermal decomposition was studied by using TG and DTA techniques. LMO loses its two moles of water between 75 and 170° to give the anhydrous product, which decomposes in three stages between 240 and 380°. The first two stages occur in the temperature ranges 240–280° and 280–305°, to give intermediates with the tentative compositions Li₆[Mo₆O₁₉(C₂O₄)₂] and Li₆[Mo₆O₂₀(C₂O₄)], respectively. In the third stage, which extends up to 380°, Li₆[Mo₆O₂₀(C₂O₄)] decomposes to give the end-product, Li₂Mo₂O₇.

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Zusammenfassung Ein neuer Molybdän(VI)-Komplex der Formel Li₂[Mo₂O₆(C₂O₄)] · 2 H₂O (LMO) wurde dargestellt und durch chemische Analyse und IR-spektroskopisch charakterisiert. Die thermische Zersetzung dieses Komplexes wurde mittels TG und DTA untersucht. LMO verliert die zwei Wassermoleküle zwischen 75 und 170° unter Bildung des wasserfreien Produktes, das zwischen 240 und 380° in drei Stufen zersetzt wird. Die in den Temperaturbereich von 240–280° und 280–305° verlaufenden ersten zwei Reaktionsschritte ergeben Intermediäre der tentativen Zusammensetzung Li₆[Mo₆O₁₉(C₂O₄)₂] bzw. Li₆[Mo₆O₂₀(C₂O₄)]. In dem sich bis 380° erstreckenden dritten Reaktionsschritt wird Li₆[Mo₆O₂₀(C₂O₄)] unter Bildung des Endproduktes Li₂Mo₂O₇ zersetzt.

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Li₂[MO₂O₆(C₂O₄] · 2 ₂ . . - 70–170° , , 240–380°. 240–280° 280–305° - Li₆[Mo₆O₁₉(C₂O₄)₂] Li₆[Mo₆O₂₀(C₂O₄)]. - 380° Li₂Mo₂O₇.

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The authors are grateful to Prof. S. N. Tandon, Head of the Chemistry Department, for providing the research facilities.