On the dioximine complexes of transition metals

Twelve new complexes NH₄[Co(DH)₂(SO₃)(amine)]·t H₂O (DH ₂=dimethylglyoxime) have been synthesized and characterized. Their i.r. spectra show the SO₃ to be co-ordinated to the Co atom through the S atom. The thermal decompositions of a series of derivatives of this type have been investigated with a derivatograph. The first process is an endothermic dehydration reaction, occurring in a single stage or in two successive ones. The loss of the crystallization water is followed by another endothermic reaction, without a clear stoichiometry, which is referred to as deamination. At higher temperatures, exothermic pyrolysis processes occur. From the TG curves, kinetic parameters have been derived for the dehydration and deamination reactions.

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Zusammenfassung Zwölf neue Komplexe der allgemeinen Formel NH₄[Co(DH)₂(SO₃)(amin)]·t H₂O (DH=Dimethylglyoxim) wurden synthetisiert und charakterisiert. Die IR-Spektren zeigen, daß SO₃ über das S-Atom koordinativ an das Co-Atom gebunden ist. Die thermische Zersetzung einer Reihe von Derivaten dieses Typs wurde mittels eines Derivatographen untersucht. Der erste Prozeß ist die in einem einzigen oder in zwei aufeinander folgenden Schritten verlaufende endotherme Dehydratisierung. Auf die Abgabe des Kristallwassers folgt eine andere endotherme Reaktion unklarer Stöchiometrie, die als Deaminierung bezeichnet wird. Bei höheren Temperaturen verlaufen exotherme Pyrolyseprozesse. Aus den TG-Kurven wurden kinetische Parameter für die Dehydratisierung und die Deaminierung bestimmt.

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NH₄Co(DH)₂(SO₃)(a)]·tH₂O, DH ₂ — . , . . , . «». . .

     

Preparation and properties of high dispersity palladium catalysts

Preparation methods for monodisperse sols of palladium with 9, 15, 30 and 75 Å particles are suggested. It has been revealed that with decreasing size of palladium particles (d25 Å), the dissolved hydrogen species disappear. As a result, their behavior in dimethyl ethynyl carbinol hydrogenation is close to the platinum properties.

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9, 15, 30, 75 Å. , (d25 Å) , .

     

Photochemical reactions of anthraquinone with hydrocarbons in the presence and absence of oxygen: Trapping of radical intermediates

Radical intermediates formed at 25°C in the presence and absence of oxygen during the photolysis of anthraquinone in aromatic, cyclic and aliphatic hydrocarbon solvents were trapped by 2,6-dichloronitrosobenzene, 2,6-dibromonitrosobenzene and 2,4,6-tribromonitrosobenzene. The resulting nitroxide radicals have been characterized in situ by ESR spectra.

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: 2,6-, 2,6- 2,4,6-— , , 25°C. .

     

Measurement of the dispersity of supported ruthenium catalysts by oxygen chemisorption

A highly dispersed (Ø (Ru)<10 Å, from electron microscopy) Al₂O₃-supported catalyst and not so well dispersed silica supported Pt, Ru, Pt, Ru-alloy catalysts were investigated. Oxygen coverage of Ru is found to be close to 2 at 20 °C over the monometallic Ru catalysts as well as over the Pt, Ru-alloy catalysts.

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(Ø (Ru)<10 Å ) Al₂O₃ Pt Ru Pt Ru . Ru 2 20°C Ru, Pt Ru.

     

Oxygen interaction with rhodium at low pressures II. Oxygen desorption

Oxygen desorption on polycrystalline Rh and single crystal Rh(100) at 400–1600 K has been studied using thermal desorption and numerical calculation methods. With low surface coverages (<0.3) the adsorbed oxygen particles pentrate the metal and the diffuse back to the surface (peak ₂). At >0.3 the processes of formation/decomposition of surface oxide Rh₂O₃ takes place (peak ₁).

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- O₂ Rh Rh(100) 400–1600 . (<0,3) O ë ( ₂), >0,3 - - (Rh₂O₃) ( ₁).

     

Structure, activity and selectivity of V2O5-TiO2 catalysts for o-xylene conversion

The formation of needle shaped crystallites of V₆O₁₃ at low V concentrations on V₂O₅-anatase coated catalysts explains the low selectivity for phthalic anhydride during o-xylene oxidation. The (010) plane of V-oxide, most active for selective oxidation of o-xylene, is not accessible and the contact of this plane with the anatase faces promotes the anatase-rutile transformation and the incorporation and blocking of V⁴⁺ ions.

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V₆O₁₃ V , V₂O₅-, -. (010) , -, , - V⁺⁴.

     

Mechanism of hydrogenation of nitric oxide on platinum catalysts in acidic solution

To explain the mechanism of hydrogenation of NO in 2 M H₂SO₄, the kinetics of the hydrogenation of hydroxylamine to ammonia were studied. The rate constant of this reaction was compared with the ratio of rates at which NH₃OH⁺ and NH ₄ ⁺ were generated by the hydrogenation of NO. Both of these products are formed from NO via parallel reactions of a common intermediate. A mechanism for the hydrogenation of NO and the shift of the catalyst of the potential is proposed.

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NO 2M H₂SO₄ . NH₃OH⁺ NH₄ ⁺ NO. NO . . ., NO .

     

Infrared spectroscopic study of the interaction between furan and a vanadium oxide catalyst

The results of the infrared spectroscopic study of the interaction between furan and a vanadium oxide catalyst permit to suppose that the intermediates in furan oxidation are surface succinyl oxide and maleates.

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, , , - .

     

Thermal characterization of bismaleimide blends

4,4-bismaleimidophenyl methane (BM) and 3,3-bismaleimidophenyl sulfone (BS) were blended in solution using weight ratios 31 (MS31), 21 (MS21), 11 (MS11), 12 (MS12) and 13 (MS13). Chain extended bismaleimide resins were also prepared by treating BS/BM with 4,4-diaminodiphenyl ether in molar ratios of 10.3 (BM-E and BS-E resins). These resins were also blended with bismaleimides and the curing characteristics were evaluated by differential scanning calorimetry. Increase in BM content in BMBS blends or increase in chain extended bismaleimide content in BM-EBS or BS-E BM blends resulted in a reduction of melting and curing temperatures. Indication about the extent of cross-linking was obtained from solubility measurements (in DMF) of isothermally cured resins (180 °C, lh and 220 °C, lh in an air oven). Thermogravimetric analysis of samples isothermally cured at 180 °C and 220 °C (lh each) was carried out in nitrogen atmosphere. Improvement in thermal stability of chain extended bismaleimides was observed on blending.

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Zusammenfassung 4,4-Bismalimidophenyl-methan (BM) und 3,3-Bismalimidophenyl-sulfon (BS) wurden in Lösung in den Gewichtsverhältnissen 31 (MS31), 21 (MS21), 11 (MS11), 12 (MS12) und 13 (MS13) gemischt. Auch kettenpolymerisierten Bismalimid-Harze wurden durch Behandlung von BS/BM mit Diaminodiphenylether im Molverhältnis 10,3 dargestellt (BM-E- und BS-E-Harze). Die Kennwerte der Aushärtung von Mischungen dieser Harze mit den Bismalimiden wurden mittels DSC ermittelt. Eine Erhöhung des BM-Gehaltes in den BM BS-Mischungen oder des Gehaltes der BM-E BS oder BS-E-Mischungen an kettenpolymerisierten Bismalimiden führt zu einer Erniedrigung der Schmelz- und Aushärtetemperaturen. Hinweise über den Vernetzungsgrad wurden aus Löslichkeitsmessungen (in DMF) von Isotherm (je 1 Stunde bei 180 und 220 °C in Luft) gehärteten Harzen erhalten. Die thermogravimetrische Analyse der Isotherm bei 180 bzw. 220 °C 1 Stunde ausgehärteten Proben wurde in Stickstoffatmosphäre ausgeführt. Die thermische Stabilität der Bismalimide wird durch Verschneiden verbessert.

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4,4-- () 3,3-- () 31 (MC 31), 21 (MC 21), 11 (MC 11), 12 (MC 12) 13 (MC13). - / 4,4- 10,3 ( - C-). - . - - - - , . ( 1 180 220°) . . - .

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The financial assistance provided by Department of Science and Technology is gratefully acknowledged.     

Study of cyclohexane conversion on A Pt/Al2O3 catalyst under reforming conditions by a gradientless method

A common type of rate equations for hydrocarbon conversions under reforming conditions has been shown, resulting from the features of the hydrocarbons and hydrogen adsorption on the Pt/Al₂O₃ catalyst. This has been confirmed by variations in the rate of cyclohexane conversion observed upon the introduction of methane into the reaction mixture. Methane does not react but is strongly adsorbed on the catalyst surface.

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, . , , .

     

Construction of a thermoanalyzer for DTA-TD-TMAG-T measurements on metals up to 1100 °C

A thermoanalyzer is described for the simultaneous testing of metals and alloys by three methods: differential thermal analysis (DTA), thermal dilatometry (TD) and thermomagnetometry (TMAG). One reference specimen is used as a standard for each of the above kinds of analysis. Measurements can be performed in vacuum or in a static or dynamic atmosphere of gases at any pressure between normal and 5× 10^–5 Torr. The temperature of the sample can be changed linearly in the range 20–1100 °C. DTA and TD are performed classically, whereas TMAG is based on the temperature and magnetic field-dependences of the reversible magnetic susceptibility of the sample. Some analysis results are presented.

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Zusammenfassung Es wird ein Thermoanalysator zur simultanen Untersuchung von Metallen und Legierungen durch drei Methoden beschrieben: Differentialthermoanalyse (DTA), Thermodilatometrie (TD) und Thermomagnetometrie (TMAG). Für alle drei Verfahren wurde die gleiche Referenzsubstanz als Standard benutzt. Messungen können im Vakuum oder is statischer bzw. bewegter Atmosphäre von Gasen beliebigen Druckes zwischen Normaldruck und 5·10^–5 Torr durchgeführt werden. Die Temperatur der Probe kann zwischen 20 und 1100 °C linear variiert werden. Während DTA und TG die herkömmlichen Verfahren zu Grunde liegen, basiert TMAG auf der Temperatur- und Magnetfeldabhängigkeit der reversiblen magnetischen Suszeptibilität der Probe. Einige Analysenergebnisse wurden dargestellt.

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: (), () (). . , 5·10^–5 . 20–1100°. , . .

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Presented at the 4th European Symposium on Thermal Analysis and Calorimetry, Jena, GDR, August 1987.     

Thermal decompositions of Y,La and light lanthanide thiodiglycolates

The conditions of thermal decomposition of the thiodiglycolates of Y, La and light lanthanides from Ce to Gd have been studied. On heating, these complexes decompose in various ways. Hydrated thiodiglycolates of La,Ce(III), Pr(III) and Gd lose crystallization water in one step, while those of Y, Nd, Sm and Eu(III) do so in two steps. The anhydrous complexes subsequently decompose in several steps to the oxysulfates Ln₂O_3–x((SO₄)_x.

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Zusammenfassung Bedingungen der thermischen Zersetzung der Thiodiglycolate von Y, La und den leichten Lanthaniden von Ce bis Gd wurden untersucht. Beim Erhitzen zersetzen sich diese Komplexe auf verschiedene Weise. Hydratisierte Thiodiglycolate von La, Ce(III), Pr(III) und Gd verlieren das Kristallwasser in einem Schritt, die von Y, Nd, Sm, und Eu(III) dagegen in zwei Schritten. Die wasserfreien Komplexe zersetzen sich in mehreren Schritten zu den Oxysulfaten Ln₂O_3–x(SO₄)_x.

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. . . , , , , , . Ln₂O_3–x(SO₄)_x.

     

Hydrolysis kinetics of the acid and base species of oxacillin in aqueous solution

Using the method of initial rates, a study has been carried out on the different kinetic behavior of the acid and base forms of oxacillin. The acid catalytic constants of both species are determined. The acid form is much more stable with respect to hydrolysis.

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, . . , .

     

Conversion of hydrocarbons on supported catalysts prepared via decomposition of surface complexes. Preparation and properties of (Ga+Pt)/SiO2 and (Ga+Pt)/Al2O3 catalysts

The addition of gallium is shown to increase Pt dispersity and its stability to deactivation in n-hexane dehydrocyclization, to decrease the rate of n-hexane hydrogenolysis and to increase the selectivity to benzene, apparently, due to the interaction of Pt clusters with surface Ga ions.

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, -, - . .

     

Thermoanalytical studies on the preparation of industrial crystalline aluminium sulphate

Changes in the water content of aluminium sulphate hydrate were investigated gravimetrically at room temperature in air with different relative humidities. The samples conditioned in this way were characterized by thermoanalytical (TG, DTG, DSC) and X-ray diffraction measurements. Industrial aluminium sulphate hydrate obtained by freezing the melt has a partly crystalline structure. After grinding, this material crystallizes during storage. This process requires a humid atmosphere; increasing relative humidity brings about more intensive crystallization.It was found that the crystallization of aluminium sulphate from the melt is facilitated by a higher water content of the melt.

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Zusammenfassung VerÄnderungen des Wassergehalts von Aluminiumsulfat-Hydrat bei Zimmertemperatur in Luft unterschiedlicher relativer Feuchtigkeit wurden gravimetrisch untersucht. Die auf diese Weise konditionierten Proben wurden durch thermoanalytische (TG, DTG, DSC) und röntgendiffraktometrische Messungen charakterisiert. Durch Erstarren der Schmelze erhaltenes industrielles Aluminiumsulfat-Hydrat ist teilweise kristallin. Nach dem Mahlen kristallisiert dieses Material wÄhrend der Lagerung. Dieser Proze\ erfordert eine feuchte AtmosphÄre, wobei sich der Kristallisationsgrad mit steigender relativer Feuchtigkeit erhöht. Es wurde festgestellt, da\ die Kristallisation des Aluminiumsulfats durch einen höheren Wassergehalt der Schmelze gefördert wird.

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. , , . , , . . , . , .

     

Some investigations on the photostabilization of polypropylene

The effect of substituted hydroxybenzophenone, benzotriazole and organic metal complexes on the photooxidation of PP films has been studied. It has been established that NiDBTC added in 1.0 wt. % is the most effective photostabilizer.While in the case of other stabilizers there is a slight increase in the Co content even during the induction period, with the application of NiDBTC practically no oxidation can be observed before the stabilizer completely disappears. This means that NiDBTC inhibits the photooxidation of the polymer even in low concentration.

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, - . , Ni, 1,0 . %. . , Ni , . , Ni .

     

Effect of the roughness factor on the surface oxidation of ruthenium catalysts

The surface oxidation of ruthenium catalysts with different roughness factor values has been analyzed. It is shown that electro formation of oxidized species on the exposed surface of ruthenium is strongly affected by the rougher characteristics of the surface. This effect has been explained through the addition and removal of protons to and from the oxidized species.

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. , . .

     

Application of thermal analysis for quantitative nitrogen determination in fertilizers

DSC and DTA techniques have been used to determine nitrogen present in the form of ammonium nitrate in fertilizers. The optimum conditions for the investigations were determined for both techniques. By determining peak area, i.e. the enthalpy of the ammonium nitrate crystal transformation II I, it was possible to determine the nitrogen content in ammonium nitrate and in lime ammonium nitrate by DSC with average deviations of 0.44 and 0.91%,respectively. Using DTA and the enthalpy of the ammonium nitrate crystal transformation IV III, the average deviation of nitrogen determination in lime/ammonium nitrate was 1.09%.

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Zusammenfassung DSC und DTA wurden zur Bestimmung des in Düngemitteln in Form von Ammoniumnitrat vorliegenden Stickstoffs benutzt. Für beide Techniken wurden die optimalen Untersuchungsbedingungen ermittelt. Durch Bestimmung der Peakfläche, d. h. der Enthalpie der Kristalltransformation II I des Ammoniumnitrats konnte der Stickstoffgehalt in Ammoniumnitrat und in Kalk/Ammoniumnitrat mittels DSC mit mittleren Abweichungen von 0.44 bzw. 0.91% bestimmt werden. Aus der Kristalltransformation IV III des Ammoniumnitrats ergibt sich bei Benutzung der DTA-Methode eine mittlere Abweichung von 1.09% für die Stickstoffbestimmung in Kalk/Ammoniumnitrat.

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, . . , , (III) , — . , , 0,44 0,91%. IVIII , - 1,09%.

     

Catalytic activity of palladium-containing zeolites in the complete oxidation of benzene

The dependence of palladium distribution in zeolites on the temperature of thermal treatment has been established from the data on oxygen chemisorption and the statistical processing of electron micrographs. The influence of palladium distribution in zeolites on their catalytic activity towards the complete oxidation of benzene has been shown.

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