Br?nsted sites in H-forms of faujasites obtained from ammonium and guanidine forms

The infrared spectra of H-forms of Y zeolite made from the guanidine and ammonium forms were compared. The Brönsted acid sites have been characterized by adsorption of pyridine. Good correlation between the concentration of Brönsted acid sites and the catalytic activity of the samples has been found. It was concluded that guanidine cations limited localization of OH groups on the surface of the supercages.

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, . , . . , OH .

     

Interaction between particles in solution and the mechanism of dihydrogen activation in base catalyzed isotope exchange reactions

A previously suggested mechanism for the H-D isotope exchange of dihydrogen with aqueous alkaline and amide-ammonia solutions is discussed to be generalized and extended to hydrogen isotope exhange with other protolytic solvents.

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- () - () - (). ().

     

Influence of pressure reduction on the shapes of thermoanalytical curves of red muds

The effect of reduction of pressure on the shapes of the TG, DTG and DTA curves and the mass-spectra of hydroxide and carbonate phases was investigated in some typical Hungarian red muds. The pressure change caused different decomposition rates of the phases and resulted in better separation of the overlapping thermal curves; this led to advantages as regards phase analysis. For phase analysis the red muds were extracted with water, and the extracts and solid residues were identified by IR- and X-ray methods.

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Zusammenfassung Die Wirkung der Druckänderung auf die Form der TG-, DTG- und DTA-Kurven, sowie der MS-Spektra der Hydroxid- und Carbonatphasen in einigen typischen ungarischen Rotschlamm-Sorten wurde geprüft. Die Druckänderung verursachte verschiedene Zersetzungsgeschwindigkeiten der Phasen, führte zur besseren Auftrennung der sich überlappenden thermischen Kurven, und war ausserdem auch hinsichtlich der Phasenanalyse vom Vorteil. Zur Phasenanalyse wurden die Rotschlämme mit Wasser extrahiert und die Extrakte und festen Rückstände mittels IR- und Röntgenmethoden identifiziert.

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Résumé On a étudié dans quelques espèces typiques de boues rouges de Hongrie l'effet des variations de pression sur la forme des courbes TG, TGD et ATD ainsi que les spectres de masse des phases hydroxyde et carbonate. La variation de la pression entraîne des vitesses de décomposition différentes. Il en résulte une meilleure séparation des phénomènes dans le cas où ceux-ci se chevauchent ainsi que des avantages du point de vue de l'analyse des phases. L'analyse des phases présentes dans les boues rouges a été effectuée par extraction à l'eau. Les extraits et les résidus solides ont été identifiés par spectrométrie infrarouge et par diffraction des rayons X.

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, - . , , . .

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Paper presented at the Scientific Session on Thermal Analysis held at Balatonfüred, Hungary, on 14–16 October 1976.     

Correlation between acid strength (Ho) and ammonia desorption temperature for aluminas and silica-aluminas

Correlation between the temperature at which a base is desorbed and the acid strength (H_o) of the sites set free by it, was looked for. Ammonia was employed as base. A linear correlation of the type H_o=+/T (K) is valid with and constants, dependent on the adsorbate and the adsorbent.

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(H_o) , . H_o=+/T (K), .

     

Investigation of surface phenomena on solid catalysts by thermogravimetry

Thermogravimetry was applied to the investigation of the phenomena of adsorption, chemisorption, desorption and surface reactions on solid catalysts. The measurements were carried out with 13 NaX and NaY type zeolites and with silica gels treated with sodium hydroxide, in the presence of cumene and methanol. On the basis of the quantitative results it is possible to give an interpretation of surface phenomena and to establish the existence of various active centres on the surface of the catalysts.

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Zusammenfassung Adsorptions-, Chemisorptions- und Desorptionserscheinungen, sowie Oberflächenreaktionen an festen Katalysatoren wurden thermogravimetrisch untersucht. Die Messungen wurden an Zeoliten der Typen 13 NaX und NaY und an mit Natriumhydroxid behandelten Silikagelen in Gegenwart von Cumol und Methanol durchgeführt. Aufgrund der quantitativen Ergebnisse war es möglich, die Oberflächenerscheinungen zu deuten und das Vorhandensein von verschiedenen aktiven Zentren an der Katalysatoroberfläche nachzuweisen.

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Résumé On a appliqué la méthode thermogravimétrique à l'étude des phénomènes d'adsorption, de chemisorption et de désorption ainsi qu'aux réactions de surface sur des catalyseurs solides. Les mesures ont été effectuées sur zéolites de type 13 NaX et NaY et sur des silicagels traités par la soude en présence de cumène et de méthanol. Des résultats quantitatifs permettent de donner une interprétation des phénomènes de surface et d'établir l'existence de divers centres actifs à la surface des catalyseurs.

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, , , . , , , , . 13 NaX NaY , . .

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The authors express their gratitude to Prof. S. Malinowski for help and discussion and to Mr. W. Dziklinski for his technical help.     

Ba(OH)2 as catalyst in organic reactions, part XIV. Michael addition catalyzed by barium complex salts in the homogeneous phase

Michael addition to chalcone is catalyzed by barium complex salts in the homogeneous phase under various conditions. The nature of these intermediates is analyzed. These complex salts are described for the first time. The Michael adduct of malonodinitrile to chalcone is described for the first time.

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, , . . . . .

     

Thermometrische Prüfung von Bromadditionsreaktionen zur StrukturaufklÄrung und quantitativen Analyse

Zusammenfassung Durch Direktthermometrie lie\en sich organische Substanzen mit Doppelbindung z. B. verschiedene Arzneien, wie Chinin, Vasalgin mittels Bromwasserreagens quantitativ bestimmen. Die Ermittlung der Werte der ReaktionswÄrmen oder WÄrmeent-wicklungsgeschwindigkeiten ermöglicht eine schnelle Unterscheidung der cis- und trans-Isomeren wie Fumar- und MaleinsÄure, öl- und ElaidinsÄure usw.

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Organic substances containing double bonds, e.g. allyl alcohol, and different medicaments (quinine, vasalgin), were determined with bromine water by direct injection enthalpimetry. Measurement of the reaction heat or the rate of evolution of heat permits simple and rapid distinction of cis and trans isomers: fumaric and maleic acid, or oleic and elaidinic acid.

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Résumé Des substances organiques à liaisons doubles (par ex. l'alcool allylique, médicaments divers, la quinine, la vasalgine) ont été dosés par l'eau de brome, en utilisant la thermométrie directe. La mesure des chaleurs de réaction ou des vitesses du dégagement calorifique permettent une distinction rapide entre les isomères cis et trans: les acides fumarique et maléique, oléique et élaÏdique.

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, , , , (, ) . - -: , .

     

Kinetics of edta catalyzed oxidation of I? by Cr(VI)

The activity of various iron-containing ore catalysts during hydrogenation of Kansk-Achinsk lignite into liquid products in H-donor solvent (tetraline) has been studied. Ore samples contained pyrite, hematite and magnetite minerals. The most active appear to be pyrite samples. The catalytic effect of ore systems is, apparently, associated with the fact that during hydrogenation more active than tetraline H-donors are formed due to the hydrogenation of polycyclic aromatic molecules produced by thermal destruction of lignite.

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- H- . , , . , . , , , , , .

     

Potentiometric titration of sorbed hydrogen on palladium carrier catalysts

A method of determination of adsorbed and absorbed hydrogen on palladium catalysts with carbon carriers is suggested and verified. The method allows H_ad and H_ab to be determined with an accuracy of about 10% using catalysts containing at least 5% Pd.

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- . . . 10% , , - , 5% Pd.

     

Thermal decomposition of crystalline molecular sieve (C3H7)3N-AlPO4-5

The thermal decomposition of (C₃H₇)₃N-AlPO₄-5 in inert and oxidizing gas atmospheres has been studied by TG, DTG and DTA in the temperature range 303–1273 K. The removal of tripropylamine occluded in the channels of the aluminophosphate occurs in a number of steps and is strongly influenced by the gas atmosphere.

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Zusammenfassung Die thermische Zersetzung von (C₃H₇)₃N-AlPO₄-5 wurde in inerter und oxydierender Gasatmosphäre mittels TG, DTG und DTA im Temperaturbereich von 303–1273 K untersucht. Der Austritt des in den Kanälen des Aluminiumphosphats okkludierten Tripropylamins erfolgt über eine Anzahl von Stufen und wird stark von der Gasatmosphäre beeinflußt.

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, (C₃H₇)₃N-AlPO₄-5 303–1273 . , , .

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We are grateful to Dr. V. G. Gunjikar, Mr. J. S. Gujaral and Dr. (Mrs) A. Mitra of the Special Instrument Group of our Laboratory for their co-operation in the work.     

Thermal and spectroscopic study of the solid complexes of furan-2-hydroxamic acid and several divalent metallic cations

Solid crystalline complexes of furan-2-hydroxamic acid (FHA) and six metallic divalent cations (Ca(II), Ba(II), Co(II), Ni(II), Cu(II), and Cd(II)) were prepared. In all cases the stoichiometry was 2(FHA)1 (cation). The solids were characterized by elemental analysis, TG, DSC and IR techniques.

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Zusammenfassung Es wurden feste, kristalline Komplexe von Furan-2-hydroxamsäure (FHA) und sechs verschiedenen bivalenten Metallkationen hergestellt: Ca(II), Ba(II), Co(II), Ni(II), Cu(II) und Cd(II). Die stöchiometrische Zusammensetzung betrug in allen Fällen 2(FHA)1(Kation). Die Feststoffe wurden mittels Elementaranalyse, TG-, DSC- und IR-Techniken charackterisiert.

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-2- , , , , . : 21. , , .

     

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.

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() , , () 0,5–0,7. , .

     

Measurement of reaction kinetics by a pressure rise method

Decomposition of urea nitrate in an initially evacuated system gave sigmoidal pressurevs. time curves. The experimental kinetic data fit the growing nuclei model with a measured enthalpy of activation of 142±12.5 kJ/mole as compared to 115±11.3 kJ/mole obtained thermogravimetrically. This higher value ofH is explained on the basis of two factors: 1) the inhibitory effect of the product gases and 2) self heating, whose extent increasedH by about 12.5 kJ/mole.

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Zusammenfassung Die Zersetzung von Harnstoffnitrat in einem anfanglich evakuierten System ergab sigmoide Druck-Zeit Kurven. Die kinetischen Versuchsangaben können einem Kernwachstums-Modell einer gemessenen Aktivierungsenthalpie von 142±12,5 kJ/mol angepaßt werden, im Vergleich zu den auf thermogravimetrischen Weg ermittelten Wert von 115±11.3 kJ/Mol. Dieser hohe Wert vonH, wird auf Grund zweier Faktoren erklärt: 1) der Hemmungseffekt der Produktgase und 2) Selbsterhitzung, deren AusmaßH um etwa 12.5 kJ/Mol erhöhte.

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Résumé La décomposition du nitrate d'urée dans un système initialement mis sous vide, donne des courbes sigmoïdales de pression en fonction du temps. Les données cinétiques expérimentales peuvent être ajustées à un modèle de grossissement de germes, avec une enthalpie d'activation mesurée de 142±12.5 kJ/mole, comparée à 115±11.3 kJ/mole obtenue par thermogravimétrie. Cette valeur plus élevée deH s'explique sur la base de deux facteurs: 1) l' effet inhibiteur des gaz produits et 2) phénomène d'autoéchauffement qui augmente la valeur deH d'environ 12.5 kJ/mole.

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. , 142+-12.5 / 115 + 11.3 /, . H : 1) 2) , 12.5 /.

     

Gas phase elimination reaction of ethylbromoacetate

Ethylbromoacetate was pyrolyzed in a static system and seasoned vessels at temperatures between 339.3 °C–353.3 °C and pressures between 53–166.4 Torr. The rate constant for the homogeneous unimolecular elimination is given by the following Arrhenius equation: log k₁(s^–1)=(12.62±1.01)–(195.7±9.7) kJ/mol/2.303 RT. In comparing the -bromo substituent with the -chloro one in alkyl -monohaloacetates, the former shows about the same rate as the latter. The lack of a very significant difference in rates may be due to their similar electron withdrawing effect under these reaction conditions.

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, , , 339,3 °C–353,3 °C 53–166,4 . : 10g₁ (^–1)=(12,62±1,01)–(195,7±9,7) ·^–1/2,303RT. - - - . .

     

Reduction behavior of Cu?SiO2 catalyst prepared by ion exchange for selective dehydrogenation to produce methyl formate from methanol

Reducibility of Cu–SiO₂ catalyst prepared by ion exchange method, being effective for selective dehydrogenation to produce methyl formate from methanol at lower temperatures, has been studied by a TPR technique. The results suggest that easier reduction leads to an increase of dispersity of Cu particles.

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, - , , . , , Cu.

     

Hydrogen adsorption on chromia-supported iridium catalyst

Effect of thermal pretreatment of chromia-supported iridium catalyst on hydrogen adsorption was studied. It was found that the hydrogen uptake by Ir/Cr₂O₃ was highly dependent on the reduction temperature. The catalyst proved to be resistant to sintering in oxygen atmosphere at temperatures up to 700 °C and it showed symptoms of redispersion even at 650 °C.

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. Ir/Cr₂O₃ . 700°C, , 650°C .

     

Formation of oxalates and carbonates in the thermal decompositions of alkali metal formates

The influences of gaseous and solid reactants on the yields of oxalates and carbonates in the thermal decompositions of alkali metal formates have been studied. A mechanism of formation of these products is proposed, which explains the influences of basic and acidic species formed in the medium on the thermal decompositions of the alkali metal formates.

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Zusammenfassung Der einfluß von gasförmigen und festen Reaktanten auf die Ausbeute von oxalaten und Karbonaten bei der thermischen Zersetzung von Alkalimetallformiaten wurde untersucht. Es wurde ein Mechanismus für die Bildung dieser Produkte vorgeschlagen, der den Einfluß der während der thermischen Zersetzung von Alkalimetallformiaten entstehenden Basen und Säuren erklärt.

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, . , , .

     

Oxidation of carbon monoxide with nitrous oxide over CeO2

With the help of the transient response method and fluorescence spectroscopy, it has been revealed that the title reaction proceeds by the catalyst redox transformation Ce(III)Ce(IV) over CeO₂ in great contrast to previous observations over MgO. , Ce(III)Ce(IV) CeO₂ MgO.     

Study of thermochemical conversions of alicyclic polyimides

The thermochemical conversions of certain polyimides obtained by the polycondensation of dianhydrides of alicyclic tetracarboxylic acids and 4,4-diaminodiphenyl oxide were studied by different methods of thermal analysis (thermogravimetry, mass-spectrometric evolved gas analysis, and pyrolytic gas chromatography). The thermal dissociation of dianhydride fragments according to the reverse reaction of retrodiene synthesis is the basic reaction that determines the thermal stabilities of the polymers studied. It is shown that the absence of endoethylene bonding or its substitution by oxygen in the dianhydride fragments leads to increases in the thermal stabilities of alicyclic polyimides.

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Zusammenfassung Thermochemische Umwandlungen einiger Polyimide, die durch Polykondensation der Dianhydride alicyclischer Tetracarbonsäuren mit 4,4-Diaminodiphenyloxid dargestellt waren, wurden durch verschiedene thermoanalytische Methoden (TG, massenspektrometrische EGA und Pyrolyse-Gaschromatographie) untersucht. Die thermische Spaltung der Dianhydrid-Komponente nach einer Retro-Diensynthese ist die Hauptreaktion, die die thermische Stabilität der Polymeren bestimmt. Bei Abwesenheit der endo-Ethylen-Bindung in der Dianhydrid-Komponente oder Substitution durch eine Etherbindung wird die thermische Stabilität von Polyimiden mit alicyclischen Baugruppen erhöht.

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, - , 4,4- . , , . , - , .

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The authors would like to thank Yu. A. Sazanov and L. A. Shibaev (IVS AN SSSR, Leningrad) for help in the mass-spectrometric thermal analysis of the polymers.