Free radical additions to the C=O bond of formaldehyde

The reactions between formaldehyde and n-propyl radicals were studied at 333 and 363 K. Addition to the C=O bond was found to be several times faster than abstraction of the formyl hydrogen atom. With a TST estimate of log(A/dm³ mol^–1 s^–1)=7.9±0.5, 28.0±2.1 kJ mol^–1 was obtained for the activation energy of the addition reaction.

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- 333 363 . C=O . 28.0±2.1 ^–1 , lg(A/ ^{–1 –1})=7.9±0.5 .

     

Influence of neodymium content on the catalytic properties of zeolite NDHNaY

The influence of neodymium content on the catalytic properties of a HNaY zeolite was investigated using the cracking of n-heptane as model reaction. Neodymium zeolites were found to be more active for cracking and hydrogen transfer reactions than zeolites containing lanthanum, cerium or praseodymium.

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HnaY . , , , .

     

Dependence of the catalytic properties of cobalt molybdate in propylene oxidation on the surface reduction and oxygen bond energy

The dependences of the tate of partial propylene oxidation and of oxygen bond energy on the degree of cobalt molybdate reduction has been investigated by pulse and caloremetric methods. It has been found that upon reduction, the selectivity to acrolein and the oxygen bond energy increase. The steady state under the conditions examined is characterized by 22% surface reduction and the presence of uniform oxygen with a bond energy of about 85 kcal/mol.

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. , . 22% 85 /.

     

Thermal decomposition of copper(II)phthalate monohydrate

The thermal dehydration and decomposition of copper(II) phthalate monohydrate was studied by isothermal and non-isothermal methods. The decomposition process consisted of three steps: two steps of dehydration and the third of decomposition. The kinetics of isothermal dehydration reactions follow (i) a unimolecular law up to the formation of copper(II) phthalate hemihydrate, and (ii) a phase boundary model giving anhydrous copper(II) phthalate, while the kinetics of isothermal decomposition reaction comply with the Erofeev-Avrami equation, [–ln(1–)]^1/n =Kt+C. The energies of activation for the formation of the decomposition products were calculated. The decomposition products were characterized by elemental analysis, photomicrographic observations, infrared and reflectance spectra and X-ray powder diffraction data.

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Zusammenfassung Die thermische Dehydratisierung und Zersetzung von Kupfer(II)Phthalat Monohydrat wurde durch isotherme und nichtisotherme Methoden untersucht. Der Zersetzungsvorgang bestand aus drei Stufen: zwei Stufen der Dehydratisierung und die dritte der Zersetzung. Die Kinetik der isothermen Dehydratisierungsreaktionen folgt (i) einem unimolekularen Gesetz bis zur Bildung von Kupfer(II)Phthalat Hemihydrat und (ii) einem Grenzflächen modell, das wasserfreies Kupfer(II)Phthalat ergibt, während die Kinetik der isothermen Zersetzungsreaktion der Erofeev-Avrami Gleichung, [–ln(1–)]^1/n =Kt+C genügt. Die Aktivierungsenergien für die Bildung der Zersetzungsprodukte wurden berechnet. Die Zersetzungsprodukte wurden durch Elementaranalyse, mikrophotographische Beobachtungen, Infrarot- und Remissionsspektra sowie Röntgen-Pulverdiffraktionsdaten charakterisiert.

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Résumé On a étudié, par des méthodes isothermes et non-isothermes, la déshydratation et la décomposition thermique du phtalate de cuivre(II) monohydraté. Le procèssus de décomposition consiste en trois étapes: deux étapes de déshydratation et la troisième de décomposition. La cinétique des réactions de déshydratation isotherme suit (i) une loi unimoléculaire jusqu'à la formation de phtalate de cuivre(II) hémihydraté, et (ii) un modèle de surfaces limites qui donne du phtalate de cuivre(II) anhydre, tandis que la cinétique de la réaction de décomposition isotherme satisfait l'équation d'Eroféev-Avrami: [–ln(1–)]^1/n =Kt+C. On a calculé les énergies d'activation de la formation des produits de décomposition. On a caractérisé les produits de décomposition par analyse élementaire, par des observations micrographiques, des spectres infrarouges et d'émission ainsi que par des données de diffraction sur poudre des rayons X.

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(II). : . (II) , (II). - : [-In(1-)]^1/n=Kt+. . , , , .

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One of the authors (C. M. K.) is grateful to the University of Jammu, Jammu, for the award of a Fellowship.     

Effect of reduction temperature and support on the surface electronic state of supported Pd catalysts

The effect of metal precursor, support and reduction temperature on the surface reduction of Pd on -Al₂O₃ and SiO₂ has been studied. For catalysts prepared from PdCl₂, temperatures as high as 450 °C are necessary to obtain surface Pd⁰.

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, Pd -Al₂O₃ SiO₂. , , PdCl₂, Pd^o - 450°C.

     

Spectroscopic studies of the state of Cu2+ ions in Cu?Zn?Al oxide catalysts

ESR and electronic spectroscopy have reveled that in low-temperature ZnO the copper ions form Cu–O–Cu type cluster structures with highly covalent bonds and strong exchange interaction between the ions. The nearer environment of the Cu²⁺ ions is an octahedron with distortion towards square planar coordination.

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, ZnO Cu–O–Cu . Cu²⁺- , .

     

Formation of alkyl peroxides in oxidation of alkanes by H2O2 catalyzed by transition metal complexes

Some reactions between alkanes and H₂O₂ in the presence of transition metal compounds, e.g. Cr(VI), V(V), Mn(III), Pd(II), Fe(II), yield alkyl hydroperoxides as main products.

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H₂O₂ , , Cr(VI), V(V), Mn(III), Pd(II), Fe(II), .

     

Specific activity of ruthenium for hydrogenation and hydrogenolysis of benzene in relation to metal dispersity

The specific activity V_sp of ruthenium supported on -alumina (0.084–0.84 wt.%, average particle size 1=1–7 nm) has been investigated for hydrogenation and hydrogenolysis of benzene at 80–320°C and compared with that of Ru powder of 1>1400 nm. A decrease of V_sp with increasing Ru dispersity was found for both reactions, the decrease having been more pronounced for hydrogenolysis. The effect is considered to be due mainly to an influence of dispersity of supported metal on the mode and extent of benze chemisorption.

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(V_Sp) , - (0,084–0,84 .%, 1=1–7 ), 80–320°C - 1>1400 . V_Sp , . , -, - .

     

Calculation of the mass transfer coefficient with a chemical reaction in a gas-liquid system

A solution of the problem of mass transfer in a turbulent boundary layer has been obtained with a first-order chemical reaction occurring in the liquid phase. The dependence of the enhancement factor for absorption and of the mass transfer coefficient on the model parameters can be used for building up a hierarchic model of the gas-liquid reactor.

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. .

     

The influence of CSH phase nuclei on Ca3SiO4Cl2 hydration

The influence of CSH phase nuclei on calcium chlorosilicate hydration has been studied by means of calorimetry, QXRD, DTA and TG methods.

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Zusammenfassung Mittels kalorimetrischen, QXRD-, DTA- und TG-Verfahren wurde der Einfluß von CSH Phasenkörpern auf die Hydratierung von Kalziumchlorosilikat untersucht.

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, , .

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C=CaO, S=SiO₂, H=H₂O     

Modelling of self-oscillations in the combustion of n-heptane-isooctane mixtures

A mathematical model has been constructed to describe the self-oscillation regime of the cool-flame combustion of an n-heptane-isooctane mixture. The character of the dependence of the amplitude and oscillation period on the temperature and mixture composition is in a qualitative agreement with the similar experimental data.

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, --. .

     

Synthesis of triterpene glycosides

Summary The acyl -D-glucopyranoside, the acyl -D-xylopyranoside, the acyl D- and L--arabinopyranosides, and the acyl -D-lactoside of 18-glycyrrhetic acid, and also the acyl -D-lactoside of 18-glycyrrhetic acid have been synthesized. The acid and alkaline hydrolysis of the compounds obtained has been studied.Khimiya Prirodnykh Soedinenii, Vol. 4, No. 1, pp. 13–19, 1968     

Non quasi-stationary state pyrolysis. Induction period of neopentane pyrolysis

The principle of an apparatus using an isothermal continuous flow stirred tank reactor to study homogeneous gas phase reactions at space times of the order of 1 sec is given. With this apparatus, the induction period of neopentane pyrolysis (as an example) has been clearly shown.

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, , 1 . , , .

     

Ag(I) solid solutions in zirconium dihydrogen phosphate. Thermal behaviour and phase changes

The thermal and redox behaviours of some Ag-low-converted zirconium phosphates have been investigated by thermoanalytical and X-ray methods: the conditions for obtaining Ag solid solutions in phases are reported.

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Zusammenfassung Das thermische und Redoxverhalten einiger Zirkoniumphosphate niedriger Ag-Konversion wurde durch thermoanalytische und Röntgenmethoden studiert; über die Bedingungen zum Erhalten von Ag-Festphasenlösungen in HH-Phasen wird berichtet

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Résumé On a étudié le comportement thermique et oxydo-réducteur de quelques phosphates de zirconium faiblement converti par Ag, en se servant des méthodes d'analyse thermique et des rayons X: on communique les conditions permettant d'obtenir des solutions solides d'Ag dans les phases .

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- Ag- . HH.

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Paper in part presented at the 6th ICTA, in Bayreuth (Germany), July 1980.

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We thank Dr. M. A. Massucci, of our Institute, for helpful discussions and suggestions.     

Frequencies, anharmonicities, and dissociation energies of OH groups in H-mordenite

Harmonic frequencies, anharmonicities and dissociation energies of surface hydroxy groups in H-mordenite have been determined. The application of the Lippincott-Schroeder potential function for similar problems is proposed.

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, -. - .

     

A comparative study of uncatalyzed and catalyzed oscillatory behavior of different mono-and dihydroxybenzoic acids in acidic bromate

Optimum and boundary conditions for uncatalyzed and catalyzed temporal oscillations in the redox potentials in the oxidation of mono- and dihydroxybenzoic acids in acidic bromate (H₂SO₄) have been established and compared. The number and relative positions of the functional groups, in the aromatic ring have been found to influence the oscillatory behavior. Ferroin has been found to enhance the oscillatory behavior considerably as compared to Ce(IV) and Mn(II). A probable explanation of the oscillatory behaviour of these system is suggested.

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- - (H₂SO₄). . , Ce(IV) Mn(II), . .

     

NO adsorption on tin(IV) oxide

The adsorption of NO on SnO₂ has been studied in the temperature range from 0 to 86°C, at pressures from 0.4 to 3.5 Torr. The adsorption isotherms are described by the Freundlich equation. The rate of adsorption obeys the Roginskii-Zeldovitch equation and decreases with increasing temperature. The reduction of SnO₂ with carbon monoxide results in a drop in the adsorption rate and in the amount of adsorbed NO.

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NO SnO₂ 0°–86°C 0,4–3,5 . . - . SnO₂ NO.

     

Kinetics of the thermal destruction of styrene-divinylbenzene copolymers,computed from thermoanalytical data

The process of thermal destruction of styrene-divinylbenzene copolymers, studied in a derivatograph, proceeds in one stage, as indicated by the mass loss accompanied by a characteristic endothermic peak in the range 380–400°. The determined values of the kinetic characteristicsn, E, InA, E andT ₀ allow the conclusion that an increase in the divinylbenzene content of the monomer blend used to synthetize the divinylbenzene copolymers does not result in an increased thermal stability as compared to that of polystyrene.

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Zusammenfassung Der in einem Derivatographen untersuchte thermische Zersetzungsvorgang von Styroldivinylbenzolkopolymeren verläuft in einer Phase, welche durch Massenverlust angezeigt und durch einen charakteristischen endothermen Peak im Bereich von 380 ... 400° angewiesen wird. Die ermittelten kinetischen Charakteristikan, E, lnA, E, T ₀ gestatten die Schlußfolgerung, daß die Zunahme des Divinylbenzolgehalts in dem zur Synthese der Divinylbenzolkopolymeren verwendeten Monomergemisch im Vergleich zu der des Polystyrols, keine erhöhte Thermostabilität herbeiführt.

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- 380 ÷ 400°. (, , ln, , ₀) , .

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The authors are grateful to V. L. Bogatyrev and V. I. Firsov for raising the subject and for supplying the copolymer samples with fixed divinylbenzene contents.     

Acid strength distributions in the Mo?Al?Si and the Ni?Mo?Al oxide systems determined by ammonia adsorption

Acid strength distributions of Mo–Al–Si and Ni–Mo–Al oxide systems have been found by means of a relationship that gives pK_a values from amounts of ammonia adsorption. Molybdenum is suggested to cause a homogenization in the acid strength distribution of alumina but a heterogenization in silicaalumina, whereas nickel is found to neutralize strong acid sites inherent to molybdenum.

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Mo–Al–Si Ni–Mo–Al , . , , .