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. , , .

     

XPS studies of Cu-Cr catalyst deactivation in catalytic heat generators

Changes in the valence state of transition metal cations on the CuCr₂O₄/–Al₂O₃ catalyst under its deactivation in catalytic heat generators have been studied by the XPS method. Partial reduction of the catalyst active component has been revealed. It has been established that a freshly prepared catalyst contains Cr(VI) that is most likely responsible for its high initial activity.

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CuCr₂O₄/–Al₂O₃ (). , . , Cr(VI), .

     

Chemiluminescence and auto-oscillations in the (S?Cr2O72+?UO22+) system

Quasi-harmonic oscillations of chemiluminescence intensity at certain concentrations of the components for the (S–Cr₂O ₇ ^2– –UO ₂ ²⁺ ) system in concentrated sulfuric acid and chemiluminescence and dark stages with the participation of intermediates Cr(V), U(IV) and sulfur peroxide radicals (HS₂O₆ ^.) have been discovered. Chemiluminescence is attributed to the interaction of HS₂O₆ ^. compounds. The processes of deactivation of the excited states of uranyl involve the participation of Cr(V). A scheme for the oscillation chemiluminescence reactions is suggested.

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(S–Cr₂O ₇ ^2– –UO ₂ ²⁺ ) H₂SO₄ , . Cr(V), U(IV) (HS₂O₆ ^.) HS₂O₆ ^. Cr(V) . .

     

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

     

Role of tellurium in the oxidation of 1-butene on Te-doped CdMoO4

New active and selective catalysts were prepared by adding different quantities of Te to CdMoO₄. These were already selective at low Te levels, but the one with a Cd/Te/Mo ratio of 1/1/1 was specific for butadiene. The catalytic behavior of the Cd–Te–Mo–O system has been correlated mainly with the CdTeMoO₆ phase in the region rich in Te and with the CdMoO₄ phase with Te as dopant in the region poor in Te.

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Te CdMoO₄. Te, CdTeMo=111 . Cd–Te–Mo–O CdTeMoO₆ Te, CdMoO₄ Te , Te.

     

Investigation on the thermal behaviour of Mg(NO3)2·6H2O

DTA, DSC and X-ray investigations of Mg(NO₃)₂ · 6H₂O revealed a lattice transformation at (71±2) C withH=12.5 J/g, and congruent melting at 90 C withH=150.3 J/g. The results of the DTA investigations on different Mg(NO₃)₂-H₂O samples are in good agreement with those of solubility investigations. The melting enthalpy of Mg(NO₃)₃ · 6H₂O is lowered considerably by deviation from the stoichiometric water content of the compound. The results allow conclusions as to the application of this salt hydrate as a latent heat-storage material.

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Zusammenfassung DTA-, DSC- und röntgenographische Untersuchungen von Mg(NO₃)₂ · 6H₂O zeigten die Existenz einer Gitterumwandlung bei (71±2) C mitH=12.5 J/g und ein kongruentes Schmelzen bei 90 C mitH=150.3 J/g. Die Ergebnisse der DTA-Untersuchungen an verschiedenen Mg(NO₃)₂-H₂O Proben stehen in guter übereinstimmung mit denen von Löslichkeitsuntersuchungen. Durch ein Abweichen vom stöchiometrischen Wassergehalt der Verbindung wird die Schmelzenthalpie von Mg(NO₃)₂ · 6H₂O beträchtlich vermindert. Die Ergebnisse ermöglichen Aussagen zur Anwendbarkeit dieses Salzhydrates als Wärmespeichermedium.

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, 71±2 H=12,5 · 90 H=150,3 ·^–1. Mg(NO₃)₂-H₂O . . .

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We thank Dr. Flammersheim, Department of Chemistry, FSU, Jena, for the DSC measueements.     

Thermal decomposition of ammonium nitrate dispersed in a multicomponent nitrate system

To obtain the kinetic curves of thermal decomposition of ammonium nitrate occurring together with decomposition of metal nitrates contained in a mixture, the ammonia contents evolved from samples heated under thermoanalytical conditions were determined by the Kjeldahl method.

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Zusammenfassung Der aus unter thermoanalytischen -Bedingungen erhitzten Proben freigesetzte Ammoniakgehalt wird durch das Kjeldahlverfahren bestimmt, um die kinetischen Kurven der thermischen Zersetzung von Ammoniumnitrat zusammen mit der Zersetzung von Metallnitraten in Gemischen zu erhalten.

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, , , .

     

Cracking of cumene on vanadium doped silica-alumina

The influence of small admixtures of vanadium on the activity of a silica-alumina catalyst in cumene cracking has been investigated. A correlation has been established between the catalytic and acidic properties of the vanadium doped catalyst.

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. .

     

Comparison of DSC and optical transmission measurements of polymorphic transitions

Using optical measurements on single crystals, the speed of first order transitions (K₂Cr207, KNO₃, AgNO₃) was determined and compared with the strongly smeared DSC signals. Such optical measurements are proposed to select materials which are suitable for the determination of the DSC apparatus function.

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Zusammenfassung Mit Hilfe von optischen Messungen wird die Geschwindigkeit von polymorphen Phasenumwandlungen 1. Ordnung (K₂Cr₂O₇, KNO₃, AgNO₃) bestimmt und mit entsprechenden stark verschmierten DSC-Signalen verglichen. Derartige optische Messungen erscheinen geeignet, um Substanzen zu suchen, welche für die Bestimmung der DSC-Apparatefunktion geeignet sind.

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K₂Cr₂O₇, KNO₃ AgNO₃ $ , $ . , $ .

     

Identification of different structures of chromium trioxide supported on highly dispersed silica by photoluminescence

The intensity ratio of the two lines in the excitation spectra of photoluminescence of CrO₃ supported on silica depends on the chromium content and on catalyst treatment. Because of the characteristic dependence the excitation line at 410 nm is related to monochromate while the other line centered at 490–540 nm is due to di- or polychromates.

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CrO₃, , . 410 , 490–530 - - .

     

Study of interaction between trimethyl-substituted silanes and silica surface

Interaction mechanism of (CH₃)₃SiX silanes (X=Br, I, N₃, NCS, NCO, CN, NCNSi(CH₃)₃ and SO₄Si(CH₃)₃ with dehydrated silica surface has been studied by IR spectroscopy. It has been established that (CH₃)₃SiCN, (CH₃)₃SiBr, (CH₃)₃SiI and [(CH₃)₃Si]₂SO₄ can be used as soft silylating agents for endcapping.

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(CH₃)₃SiX (X=Br, I, N₃, NCS, NCO, CN, NCNSi(CH₃)₃, SO₄Si(CH₃)₃) -. , (CH₃)₃SiCN, (CH₃)₃SiBr, (CH₃)₃SiI [(CH₃)₃Si]₂SO₄ .

     

ESR studies of coke formation on zeolite catalysts for methanol conversion

Pentasil type zeolite catalysts with different SiO₂/Al₂O₃ ratios carbonized during methanol conversion at 380–420°C have been studied by the ESR method. Factors responsible for the formation of condensed coke structures on their surface have been established. SiO₂/Al₂O₃, 380–420°C. , .     

Influence of the essential features of the potential energy surface on the temperature dependence of the H+CH3→CH4 reaction

Microcanonical statistical adiabatic channel model calculations show that the temperature dependence of the limiting high pressure rate coefficients of the title reaction becomes less positive (or more negative) when the attractiveness of the radial or the attenuation of anisotropic parts of the potential energy surface increases.

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, ( ) .

     

Das System KNbO3-Nb2O5

Zusammenfassung Das System KNbO₃–Nb₂O₅ wurde mit thermoanalytischen, dilatometrischen und röntgenographischen Methoden neu untersucht. Acht ternäre Verbindungen werden im Bereich von 0–50 Mol-% K₂O gefunden. Nur K₄Nb₆O₁₇ schmilzt kongruent, alle anderen zersetzen sich peritektisch. Bei den beiden niobreichaten ternären Verbindungen handelt es sich um Hochtemperaturphasen, die sich erst oberhalb 1273 bzw. 1551 K bilden. Drei der acht Verbindungen wandeln sich mit steigender Temperatur in ihre Hochtemperaturmodifikation um.

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The KNbO₃-Nb₂O₅ system was studied by thermal analysis, dilatometry and X-ray techniques. Eight ternary compounds were found in the range from 0 to 50 mol% K₂O. Only K₄Nb₆O₇ was found to melt congruently, the other compounds decomposed peritectically. For the two ternary compounds with the highest percentage of niobium high-temperature phases were observed which were formed only above 1273 and 1551°, respectively. Three of the compounds studied transformed into their high temperature modifications on heating.

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, $ KN₃-Nb₂O₅. 0 50 % . , K₄Nb₆O₇ , $ . $ $ 1273 1551°. $ $ .

     

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.

     

Thermogravimetric and kinetic study of a clodronic acid complex formed with sodium

Thermal stability of the clodronic acid complex formed with sodium (Na₂CCl₂(HPO₃)₂ ·4H₂O) was studied using both dynamic and isothermal thermogravimetric analyses as well as mass spectra. The thermal decomposition has two stages: dehydration and loss of two molecules of hydrogen chloride. Using the isothermal TG data the first step was found to be a phase-boundary reaction while the second step obviously cannot be described with just one reaction mechanism. The final residue of the dynamic TG analyses above 810 K was found to be sodium metaphosphate.

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Zusammenfassung Sowohl mittels dynamischer und thermogravimetrischer Untersuchungen als auch and Hand von Massenspektren wurde die thermische Stabilität des mit Natrium gebildeten Säurekomplexes Na₂CCl₂(HPO₃)₂·4H₂O untersucht. Die thermische Zersetzung vollzieht sich in zwei Schritten: Dehydratation und Verlust von zwei Molekülen HCl. Auf Grund der isothermen TG Angaben ist der erste Schritt eine Phasengrenzreaktion, während der zweite Schritt mit einem einzigen Reaktionsmechanismus nicht eindeutig beschrieben werden kann. Das Endprodukt der DTG Analyse oberhalb 810 K erwies sich als Natriummethaphosphat.

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-Na₂CCl₂/HPO_3/2·4H₂O — , - . , , , . , , . 810 .

     

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.

     

Computation in kinetics, III. A new method for kinetic model search based on simultaneous regression estimation of rate constants, stoichiometry and/or reaction order

Modified samples of natural mordenites have been found to catalyze the oxidative condensation of methane to yield ethane and ethylene. The selectivity towards C₂ hydrocarbons increases, whereas the acidity of zeolites falls.

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, . C₂ .

     

A bifunctional stopcock-winch device in cells for infrared investigations of solids

A simple glass device is described acting as stopcock and winch at the same time. The device is especially suitable for the dislocation of solid sample holders in IR cells.

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, . .