Effect of preparation method of nickel-zeolite catalysts on their catalytic properties

The effect of the carrier-gas (H₂, N₂, CO₂ and air) and the influence of additives (H₂S and water vapors) in the activation of Ni- and Cr-containing zeolites on their catalytic activity have been studied in toluene disproportionation.

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- (H₂, N₂, CO₂ ) (H₂S ) , Ni Cr, .

     

The energy of the N→O bond in 3-nitroisoxazoline N-oxide

The enthalpy of combustion of 3-nitroisoxazoline has been determined as H _c ^298.15 =–414±0.3 kcal/mole and that of 3-nitroisoxazoline N-oxide as H _c ^298.15 =–406.6±0.5 kcal/mole. From the values for the heats of combustion and evaporation, the standard enthalpies of formation have been calculated and the energy of the NO bond has been evaluated at 64±3 kcal/mole.     

Heterogeneous catalytic oxidation of ethanol: A new process for acetic acid

ESR investigations on ZnO doped with various amounts of -Al₂O₃ thermally treated, are reported. Experimental data are related to the electronic structure of ZnO--Al₂O₃ and to desulfurization specific activity for natural gas.

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ZnO, -Al₂O₃. ZnO/-Al₂O₃ .

     

Cumene hydroperoxide decomposition in the presence of metal complex catalysts supported on amorphous SiO2

By the method of molecular deposition, ions of CrO ₂ ²⁺ VO³⁺ and MoO ₂ ²⁺ were supported on a matrix of amorphous SiO₂. Different types of organic ligands were supported subsequently on the surface compounds so formed. The catalytic activity of the samples was studied in the decomposition of comene hydroperoxide.

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SiO₂ CrO ₂ ²⁺ , VO³⁺, MoO ₂ ²⁺ . . .

     

Kinetic studies on MeWO4-tungstates grown under mild hydrothermal conditions (Me=Mn2+, Fe2+, Zn2+)

The reaction mechanims and the kinetics of formation of MeWO₄-tungstates (Me=Mn²⁺, Fe²⁺, Zn²⁺) have been studied by reacting metal (II) chlorides and sodium tungstate at 493 K in a special autoclave, allowing continuous removal of the reactants.

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MeWO₄ ( Me=Mn²⁺, Fe²⁺, Zn²⁺) - (II) 493 , .

     

Reaction of succinonitrile with aliphatic amines

Conclusions The reaction of primary amines with succinonitrile leads to the formation of N,N,N,N-tetrasubstituted amidines and the liberation of 2 M of NH₃. The reaction of secondary amines with succinonitrile proceeds as an intramolecular condensation with the liberation of 1 M of NH₃ per mole of the dinitrile and the formation of the ^2,5–, -dialkylaminopyrrolene.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2722–2725, December, 1973.     

Thermal decomposition of Cu(I) phosphine complexes

The thermal decomposition of Cu(I) phosphine complexes of the general types (CuXPPh₃)₄, [CuX(PPh₃)₂] and [CuX(PPh₃)₃] was investigated.The thermal decomposition of (CuXPPh₃)₄, where X denotes Cl^–, Br^–, I^–, NO ₃ ^– and PPh₃=P(C₆H₅)₃, occurs with formation of a phosphine oxide intermediate. For the remaining complexes this intermediate was not proved in the thermal decomposition.

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Zusammenfassung Die thermische Zersetzung der Cu(I)-Phosphinkomplexe vom allgemeinen Typ (CuXPPh₃)₄ und [CuX(PPh₃)₂], wie auch [CuX(PPh₃)₃] wurde untersucht. Die thermische Zersetzung von (CuXPPh₃)₄, wobei X=Cl^–, Br^–, I^– und NO ₃ ^– bedeutet und PPh₃=P(C₆H₅)₃, verläuft unter Bildung eines Phosphinoxid Zwischenproduktes, bei den übrigen Komplexen konnte dieses im Laufe der thermischen Zersetzung nicht nachgewiesen werden.

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Résumé On a étudié la décomposition thermique des complexes phosphine-Cu(I) de formule générale (CuXPPh₃)₄, [CuX(PPh₃)₂], [CuX(PPh₃)₃]. La décomposition thermique de (CuXPPh₃)₄, où X désigne Cl^–, Br^–, I^– et NO ₃ ^– , et PPh₃=P(C₆H₅)₃, s'effectue avec formation d'un oxyde de phosphine intermédiaire; avec les autres complexes, cet intermédiaire n'a pas été mis en évidence au cours de la décomposition thermique.

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(CuXPPb₃)₄ [CuX(PPh₃)₂] [CuX(PPh₃)₃]. (CuXPPh₃)₄, X=Cl^–, Br^–, I^–, NO ₃ ^– , PPh₃=(₆₅)₃ . .

     

The quest for a stable silyne, RSi ≡ CR′. The effect of bulky substituents [1]

The two major fundamental obstacles which so far have prevented theisolation of stable silynes, RSiCR (1), are: (a)the existence of more stable isomers, e.g., RRC=Si: (2) and(b) their extremely facile (exothermic) dimerication. The steric andelectronic effects of various substituents R and R (R = alkoxy,alkyl, aryl and silyl; R = alkyl and aryl groups) on the stability ofRSiCR relative to the isomeric RRC=Si:(E(1-2)), and on the energy of dimerization tothe corresponding 1,3-disilacyclobutadienes (E(D)), werestudied computationally using density functional theory (DFT) and theONIOM method. The goal was to find a combination of substituents thatwill make RSiCR more stable than RRC=Si: and whichwill also prevent its dimerization. For R = R = H,E(1-2)) = 40.7 kcal/mol (i.e., 2 islower in energy than 1), and E(D) = –104.0kcal/mol. 1, R = OH, R = m-Tbt 2,6-bis[bis(silyl)methyl]phenyl, is by 11.1 kcal/mol morestable than the isomeric silylidene 2. However, thedimerization of 1, R = OH, R = m-Tbt remains highlyexothermic (by 101 kcal/mol). 1, R = R = m-Tbt and1, R = (t-Bu)₃Si, R = m-Tbt, are by 5.8 and 2.0kcal/mol, respectively, less stable than the corresponding 2.However, the dimerization of 1, R = (t-Bu)₃Si, = m-Tbt is exothermic by only 12 kcal/mol. For1, R = (t-Bu)₃Si, and R = Tbt 2,6-bis[bis(trimethylsilyl)methyl]phenyl, the corresponding1,3-disilacyclobutadiene dimer 3, dissociates spontaneously.Thus, (t-Bu₃Si)SiCTbt is predicted to be kineticallystable towards both, isomerization to (t-Bu₃Si)TbtC=Si: anddimerization to 3, making it a viable synthetic target. Thereported energies were calculated atB3LYP/6-31G^**//B3LYP/3-21G^*; good agreement is found betweenthe DFT and the ONIOM results.     

Coordination compounds of manganese(II) with 1,10 phenanthroline

TG and DTA of the compounds Mn(phen)₂X₂ (where X=CN^–,CNO^–, NCS^– and NCSe^–), Mn(phen) (NCS)₂, Mn(NCS)₂ and Mn(NCSe)₂ (wherephen=1,10 phenanthroline) are reported and discussed. Decomposition schemes are proposed based on TG and DTA results and, where possible, the analysis and properties of intermediates formed during thermal breakdown. The decomposition of thiocyanate and selenocyanate ligands is observed to lead to an apparent slight increase in sample weight. This phenomenon is discussed in relation to buoyancy changes resulting from the release of sulphur or selenium vapours.

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Zusammenfassung TG und DTA Untersuchungen der Verbindungen Mn(phen)₂X₂ (X=CN^–, CNO^–, NCS^– und NCSe^–), Mn(phen) (NCS)₂, Mn(NCS)₂ und Mn(NCSe)₂ (phen =1.10 Phenantrolin) werden beschrieben. Anhand der TG- und DTA-Ergebnisse werden Zerzetzungsschemata vorgeschlagen und wenn möglich, Analyse und Eigenschaften der im Laufe der thermischen Zersetzung entstandenen Zwischenprodukte angegeben. Es wurde beobachtet, da\ die Zersetzung der Thiocyanat- und Selenocyanatliganden zu einer scheinbaren schwachen Zunahme des Probengewichts führt. Dieses PhÄnomen wird im Zusammenhang mit infolge der Abspaltung von Schwefel- oder SelendÄmpfen auftretenden Änderungen des Auftriebs diskutiert.

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Résumé On décrit et discute la TG et l'ATD des composés Mn(phén)₂X₂ (X=CN^–, CNO^–, NCS^– et NCSe^–), Mn(phén) (NCS)₂, Mn(NCS)₂ et Mn(NCSe)₂ (oùphén=1,10 phénantroline). On propose des schémas de décomposition à partir des résultats de TG et d'ATD et, si possible, on donne l'analyse et les propriétés des produits intermédiaires formés lors de la décomposition thermique. On a observé que la décomposition des ligands de thiocyanate et de sélénocyanate entraine une faible augmentation apparante du poids du prélèvement. On explique ce phénomène par les variations de poussée résultant du dégagement de vapeurs de soufre ou de sélénium.

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()₂₂, () (NCS)₂, Mn(NCS)₂ Mn(NCSe)₂, X=CN^–, CNO^–, NCS^–, NCSe^– =1.10. , , - , . . - , .

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We wish to express our thanks to Professor S. C. Bevan for helpful advice, particularly in connection with the buoyancy effect noted for thiocyanate and selenocyanate complexes.     

Statistical estimation of the results of differential thermal analysis of cement materials

The paper describes the results of statistical analysis of DTA diagrams. A connection is found between the second and third endothermal effects. An analysis of geometrical characteristics of theT, S andh values of DTA diagrams confirms the absence of reliable connections. The rank correlation coefficients are determined according to Spearman. Non-linear programming is formulated to obtain the kinetic dependencies of the process of hydration of cement studied by DTA.

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Zusammenfassung Es wurden die Ergebnisse von statistischen Analysen der DTA Kurven besprochen, und ein Zusammenhang zwischen dem zweiten und dritten endothermischen Effekt gefunden. Durch Untersuchung der geometrischen Kennzeichen derT, S undh Werte der DTA Diagramme konnten keine verlÄ\lichen ZusammenhÄnge festgestellt werden. Die Koeffizienten der Rangkorrelation wurden nach Spearman bestimmt. Zur KlÄrung der kinetischen ZusammenhÄnge der Zementhydratation durch DTA wurde eine nichtlineare Programmaufgabe formuliert.

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Résumé On décrit les résultats de l'analyse statistique des courbes d'ATD. On a trouvé une connexion entre le second et troisième effet endothermiques. L'analyse des caractéristiques géométriques des effets des valeursT, S eth qui apparaissent sur les courbes d'ATD confirme l'absence de connexions sûres. On a déterminé les coefficients de la corrélation de rang suivant Spearman. On propose un programme non linéaire pour obtenir les dépendances cinétiques du processus d'hydratation du ciment étudié par ATD.

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. . T, S h . . , .

     

Mechanism of non-catalytic proton exchange in aprotic low-polar solvents

The kinetics of proton exchange for the CD₃OH–(CH₃)₃COH and CD₃OH–CH₃COOH systems in various solvents have been studied by dynamic¹H and²H NMR. The mechanism of the process is discussed.

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¹H ²H CD₃OH–(CH₃)₃COH CD₃OH–CH₃COOH . .

     

The thermal decomposition reactions of bis-(pyridine-2-aldoxime)-copper(II) complexes

The thermal properties of some complexes of copper(II) with pyridine-2-aldoxime (HPAO), where the ligand appears either as the ion (PAO^–) or as a neutral molecule, were determined in vacuo and in dynamic nitrogen and oxygen gas atmospheres. The study was carried out by thermoanalytical (TG, DTG. DTA), spectroscopic and spectrometric (UV-visible, IR, diffuse reflectance, mass) techniques.The initial decomposition temperature is influenced by the number of acid hydrogens in the complex; the thermal stability sequence in vacuo is: [Cu(PAO)₂H]Cl > [Cu(PAO)₂H₂]Cl₂ > [Cu(PAO)₂]The thermal decomposition reactions occur in several separate steps, the first of which gives rise to partial ligand decomposition, the reduction of copper(II) to copper(I), and the conversion of the residual pyridine-2-aldoxime into acid amide.

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Zusammenfassung Die thermischen Eigenschaften einiger Komplexe von Kupfer(II) mit Pyridin-2-aldoxim (HPAO), in denen der Ligand entweder als Ion (PAO^–) oder als neutrales Molekül vorliegt, wurden im Vakuum und in dynamischer N₂- und O₂-Atmosphäre ermittelt. Zur Untersuchung wurden thermoanalytische (TG, DTG, DTA) und spektrometrische (UV-sichtbar, IR, diffuse Reflektionsspektrophotometrie, Massenspektrometrie) Techniken herangezogen. Die Temperatur, bei der die Zersetzung beginnt, wird durch die Zahl der sauren Wasserstoffatome im Komplex beeinflußt; für die thermische Stabilität im Vakuum gilt die Reihenfolge [Cu(PAO)₂H]Cl > [Cu(PAO)₂H₂]Cl₂ > [Cu(PAO)₂]. Die thermischen Zersetzurigsreaktionen verlaufen in mehreren diskreten Schritten, wobei der erste von diesen eine partielle Zersetzung des Liganden, die Reduktion von Kupfer(II) zu Kupfer(I) und die Konversion des verbleibenden Pyridin-2-aldoxims in das Säureamid in sich einschließt.

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-2- ( ), (-), . (, , ) , - , , - . , [Cu(PAO)₂H]CI > [Cu(PAO)₂H₂]Cl₂ > [Cu(PAO)₂] , , -2- .

     

IR study of 1-hexene isomerization on HZSM-5 zeolites

In the IR spectra of 1-hexene adsorbed on HZSM-5 zeolites with different Si/Al ratios, a new band at 1510 cm^–1 has been observed. The cis/trans-2-hexene and trans-2-hexene/1-hexene ratios were determined.

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1-, HZSM-5 Si/Al, 1510 cm^–1. /-2- -2-/1-.

     

Interaction of PM12?nVnO40?(3+n) (M=Mo, W) heteropoly complexes with nitrogen oxide

In aqueous solution, PM_12–nV_nO₄₀ ^–(3+n) (M=Mo,W) hetero-polyanions provide a much faster oxidation of NO than mononuclear VO ₂ ⁺ ions, yielding HNO₂, NO ₃ ^– and reduced HPA.

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, PM_12–nV_nO₄₀ ^–(3+n) (M=Mo,W) , VO ₂ ⁺ , NO HNO₂ NO ₃ ^– .

     

Kinetics of methanol synthesis in the presence of low-temperature catalyst

The kinetics of methanol synthesis performed in a flow circulation installation in the presence of low-temperature copperzinc-aluminium catalyst has been investigated. The application of a power kinetic equation describing the surface chemical interaction on an exponentially inhomogeneous surface is established. The effect of the volume rate and the temperature is studied and the presence of a compensation effect is proved. A possibility of determination of the temperature and the volume rate, under which conditions the side-reactions do not affect the main one, is shown on the basis of the kinetic investigations.

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-- - . - - . . , .

     

Optical and electrical measurements on CO2 covered copper films

Thin polycrystalline copper films are deposited in a special UHV cell on glass substrates and are covered step by step with CO₂. The optical and electrical properties of the films are studied in-situ by means of ellipsometry and resistivity measurements. The properties of the clean films correspond to literature data. In the case of monolayer adsorption of CO₂, the changes in the ellipsometrical angles are +1° and +0.1°, similar to the Cu/O and Cu/CO systems. Three-dimensional island growth leads to a drastical increase of and by several orders of magnitude. The resistivity first quickly decreases and then slowly reapproaches the initial value. This marked kinetics is quantitatively interpreted on the basis of a diffusion model.     

Thermal behaviour of transition metal complexes of dithiocarbazic esters. II

A thermal study (simultaneous TG and DTA measurements) was carried out on the dithiocarbazic ester complexes M[N³CH₂R₁N²C¹(S)SCH₃]₂, where M=Ni, Pt; R₁=C₆H₅. The following disproportionation reaction occurs in the solid state: II is formed through deprotonation of the CH₂ group bound to N³, whereas III is formed through protonation of N³.The influence of inductive and/or steric effects on the mechanism of this reaction is discussed, taking into account the electrochemical and X-ray data on the complexes Pt[NRNC(S)SR']₂ with differentR substituents: R=H, Ph, CH₂Ph, CH₂C₅H₁₁, CH(CH₃)₂, C(CH₃)₃; R=CH₃, CH₂Ph.These results accord with the behaviour of the same complexes in solution.

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Zusammenfassung Dithiokarbamidsäureesterkomplexe M[N³CH₂R₁N²C¹(S)SCH₃]₂ mit M=Ni, Pt und R₁=C₆H₅ wurden thermisch untersucht. Im festen Zustand spielt sich folgende Disproportionierungsreaktion ab: II wird durch Deprotonierung der an N³ gebundenen CH₂ Gruppe und III durch Protonierung des Atoms N² gebildet. Unter Zuhilfenahme der elektrochemischen und Röntgendaten der Komplexe Pt[NRNC(S)SR']₂ mit verschiedenen Substituenten R: R=H, Ph, CH₂Ph, CH₂C₅H₁₁, CH(CH₃)₂, C(CH₃)₃ und R=CH₃ bzw. CH₂Ph wurde der Einfluß von induktiven und/or sterischen Effekten auf den Reaktionsmechanismus diskutiert. Diese Ergebnisse stehen in Übereinstimmung mit dem Verhalten der Komplexe in Lösung.

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M[N³CH₂R₁N²C¹(S)SCH₃]₂, M= Ni, Pt,R ₁=C₆H₅. : II CH₂ , N³, III N². () , Pt[NRNC(S)SR]₂, R= , aR= . .

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We thank prof. A. La Ginestra for many helpful discussions on the various aspects of this work.     

Influence of substituents on rate constants for recombination of tertiary peroxy radicals

A linear correlation between the logarithm of rate constant (2k_t) for recombination of tertiary peroxy radicals (ROO)^* and ^* constants of substituents R was found to be 1g 2k_t=lg 2k _t ^° . The calculated values are 1g 2k _t ^° =4.59±0.08 and ^*=5.56±0.35.

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I (2k_t) (ROO) R: 1g 2k_t=lg 2k _t ^° . , 1g 1g 2k _t ^° =4,59±0,08 =5,56±0,35

     

Kinetics of the thermal decomposition of alkaline earth metal hydrofluorides

The thermal stability of alkaline earth metal hydrofluorides was studied by means of a Derivatograph. The values of the activation energy, reaction order and rate constant were determined. The comparison of the kinetic parameters of the decomposition process for the complete series of hydrofluorides studied led to a certain regularity in the differences in their thermal stabilities and its correlation with the strength of the hydrogen bond in their structure.

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Zusammenfassung Die thermische Stabilität von Erdalkalihydrofluoriden wurde mit Hilfe eines Derivatographen untersucht, die Werte der Aktivierungsenergien, der Reaktionsordnung und der Geschwindigkeitskonstanten bestimmt. Der Vergleich der kinetischen Parameter des Zersetzungsvorganges wies auf eine gewisse Regelmäßigkeit in ihrer verschiedenen thermischen Stabilität, die in Zusammenhang mit der Stärke ihrer strukturalen Wasserstoffbindung steht.

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Résumé On a étudié la stabilité thermique des hydrogénofluorures des métáux alcalinoterreux et déterminé les valeurs des énergies d'activation, des ordres de réaction et des constantes de vitesse de réaction à l'aide d'un Dérivatographe. Après comparaison des paramètres cinétiques on a pu établir une certaine régularité dans le changement de la stabilité thermique en corrélation avec la force de liaison de l'hydrogène dans la structure.

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. , . .