Electrical conductivity of liquid and film polymer composites filled with anion-radical salts in the presence of crown ethers

In the example of alkali metal tetracyanoquinodimethanides (M⁺TCQDM), a study has been made of the influence of resonance charge exchange on the conductivity () of polymer composites filled with anion-radical salts. When neutral molecules TCQDM⁰ are introduced into such systems, this leads to an increase in as a result of the lower activation energy of jumps between states TCQDM and TCQDM⁰. The addition of molecules of crown ethers has an analogous effect: They favor the appearance in the polymer matrix (the same as in solution) of TCQDM molecules in different charge states (TCQDM⁰, TCQDM) with migration of the cation within the limits of ternary associates (CE...M⁺...A) that are formed in systems for which the ratio of the crown ether cavity diameter to the cation diameter 1.4. Symbaticity has been found in the dependences of the electrical conductivity of films and the limiting mobility of solutions with the same composition on the parameter .Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 4, pp. 446–452, July–August, 1989.     

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.     

Invariant sets for kinetic equations

Some sets in the space of compositions possessing an invariance property are considered for a closed system, where a complex chemical reaction of a known mechanism proceeds. If the vector of concentrations belongs to such a set at a certain moment of time, it will remain within it at any succeeding moment. Some possible applications are discussed.

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, , , : , . .

     

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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, . . , .

     

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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- . .

     

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) , .

     

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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, -, - . .

     

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 .

     

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%.

     

Effect of the support on the coking of nickel catalysts in hydrocarbon steam reforming

Experiments on the coking rates of variously prepared nickel catalysts on TiO₂, Al₂O₃ and MgO in n-butane steam reforming show that changes in the relative coking rate at a rising steam excess in the gas phase depend mainly on the kind of support. The results obtained are accounted for by changes in the electron density at the site of nickel crystallite contact with the surface of various supports.

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, TiO₂, Al₂O₃ MgO, - , , , , , . .

     

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.

     

Kinetic dehydroxylation of nontronite,estimated from isothermal and nonisothermal thermogravimetry

Dehydroxylation of an American nontronite (Manito) was followed via records of isothermal and dynamic thermogravimetry. Analysis of the isothermal weight-change curves (673-753 K). was performed with the procedure suggested by Hancock and Sharp. A fourteen-kinetic equation procedure was employed for analysis of the non-isothermal weight change in the range 623–1023 K. (A second-order decomposition equation seems to fit the dehydroxylation better under these conditions). The activation energies associated with the isothermal and nonisothermal processes are 118.8 and 136.8 kJ/mol^–1, respectively.

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Zusammenfassung Anhand isothermer und herkömmlicher Thermogravimetrie wurde die Dehydroxylierung eines amerikanischen Nontronites (Manito) verfolgt. Die isothermen TG-Kurven (673–753 K) wurden mittels der von Hancock und Sharp (1972). Ein kinetisches Vierzehngleichungsverfahren wurde zur Analyse der nichtisothermen TG-Kurven im Bereich 623–1023 K angestellt. Einer Dehydroxylierung unter diesen Bedingungen scheint eine Zersetzungsgleichung zweiter Ordnung besser zu entsprechen. Die Aktivierungsenefgie für die isothermen bzw. nichtisothermen Prozesse beträgt 118,8 bzw. 136,8 kJ/mol.

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(). (673–753 ) . , 623–1023, . . , , 118,8 136,8 /.

     

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.

     

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. .

     

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 , .

     

Kinetics and thermodynamics of RuIII-EDTA complex catalyzed oxidation of diethylamine and triethylamine with molecular oxygen

The kinetics of oxidation of diethyl and triethylamine with molecular oxygen catalyzed by Ru^III (EDTA-H) (H₂O) complex has been studied at different temperatures (25–45 °C at pH 2.0 (=0.5 M KCl) as a function of amine concentration. The thermodynamic (G⁰, H⁰ and S⁰) and the activation parameters (H and S) for the reaction were computed.

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- , Ru^III (EDTA-H) (H₂O) (25–45°C) pH=2 (=0,5 M KCI) . (G⁰, H⁰ S⁰), (H S).

     

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 ^– .

     

Mössbauer study of the thermal decompositions of alkaline earth tris(oxalato)ferrates(III)

The thermal decompositions of alkaline earth tris(oxalato)ferrates(III) (Mg, Ca, Sr and Ba) have been studied by Mössbauer spectroscopy and other techniques. During the thermal decomposition, dehydration occurs first, followed by reduction to iron(II) species, and oxides and ferrites (MFe^IIIO₄) are then formed at higher temperature. In the case of strontium tris(oxalato)ferrate(III), strontium ferrite (SrFe^IVO₄) is formed at 700°.

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Zusammenfassung Die thermische Zersetzung von Tris(oxalato)ferraten(III) der Erdalkalimetalle (Mg, Ca, Sr, Ba) wurde durch Mössbauer-Spektroskopie und andere Techniken untersucht. Im Verlaufe der thermischen Zersetzung verläuft zunächst die Dehydratisierung, gefolgt von der Reduktion zu Eisen(II)-Species. Oxide und Ferrite (MFe^IIIO₄) werden danach bei höheren Temperaturen gebildet. Strontium-tris(oxalato)-ferrat(III) geht bei 700 °C in Strontiumferrit (SrFe^IVO₄) über.

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() () , , ë . , , MFe^IIIO₄. 700° SrFe^IVO₄.